Remove LLVM 8.0.1 files.

1 files changed, 0 insertions, 5678 deletions

diff --git a/gnu/llvm/tools/clang/lib/Sema/SemaTemplateDeduction.cpp b/gnu/llvm/tools/clang/lib/Sema/SemaTemplateDeduction.cpp
deleted file mode 100644
index f2f989ce124..00000000000
--- a/gnu/llvm/tools/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ /dev/null
@@ -1,5678 +0,0 @@
-//===- SemaTemplateDeduction.cpp - Template Argument Deduction ------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements C++ template argument deduction.
-//
-//===----------------------------------------------------------------------===//
-
-#include "clang/Sema/TemplateDeduction.h"
-#include "TreeTransform.h"
-#include "TypeLocBuilder.h"
-#include "clang/AST/ASTContext.h"
-#include "clang/AST/ASTLambda.h"
-#include "clang/AST/Decl.h"
-#include "clang/AST/DeclAccessPair.h"
-#include "clang/AST/DeclBase.h"
-#include "clang/AST/DeclCXX.h"
-#include "clang/AST/DeclTemplate.h"
-#include "clang/AST/DeclarationName.h"
-#include "clang/AST/Expr.h"
-#include "clang/AST/ExprCXX.h"
-#include "clang/AST/NestedNameSpecifier.h"
-#include "clang/AST/TemplateBase.h"
-#include "clang/AST/TemplateName.h"
-#include "clang/AST/Type.h"
-#include "clang/AST/TypeLoc.h"
-#include "clang/AST/UnresolvedSet.h"
-#include "clang/Basic/AddressSpaces.h"
-#include "clang/Basic/ExceptionSpecificationType.h"
-#include "clang/Basic/LLVM.h"
-#include "clang/Basic/LangOptions.h"
-#include "clang/Basic/PartialDiagnostic.h"
-#include "clang/Basic/SourceLocation.h"
-#include "clang/Basic/Specifiers.h"
-#include "clang/Sema/Ownership.h"
-#include "clang/Sema/Sema.h"
-#include "clang/Sema/Template.h"
-#include "llvm/ADT/APInt.h"
-#include "llvm/ADT/APSInt.h"
-#include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/FoldingSet.h"
-#include "llvm/ADT/Optional.h"
-#include "llvm/ADT/SmallBitVector.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/Support/Casting.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/Support/ErrorHandling.h"
-#include <algorithm>
-#include <cassert>
-#include <tuple>
-#include <utility>
-
-namespace clang {
-
-  /// Various flags that control template argument deduction.
-  ///
-  /// These flags can be bitwise-OR'd together.
-  enum TemplateDeductionFlags {
-    /// No template argument deduction flags, which indicates the
-    /// strictest results for template argument deduction (as used for, e.g.,
-    /// matching class template partial specializations).
-    TDF_None = 0,
-
-    /// Within template argument deduction from a function call, we are
-    /// matching with a parameter type for which the original parameter was
-    /// a reference.
-    TDF_ParamWithReferenceType = 0x1,
-
-    /// Within template argument deduction from a function call, we
-    /// are matching in a case where we ignore cv-qualifiers.
-    TDF_IgnoreQualifiers = 0x02,
-
-    /// Within template argument deduction from a function call,
-    /// we are matching in a case where we can perform template argument
-    /// deduction from a template-id of a derived class of the argument type.
-    TDF_DerivedClass = 0x04,
-
-    /// Allow non-dependent types to differ, e.g., when performing
-    /// template argument deduction from a function call where conversions
-    /// may apply.
-    TDF_SkipNonDependent = 0x08,
-
-    /// Whether we are performing template argument deduction for
-    /// parameters and arguments in a top-level template argument
-    TDF_TopLevelParameterTypeList = 0x10,
-
-    /// Within template argument deduction from overload resolution per
-    /// C++ [over.over] allow matching function types that are compatible in
-    /// terms of noreturn and default calling convention adjustments, or
-    /// similarly matching a declared template specialization against a
-    /// possible template, per C++ [temp.deduct.decl]. In either case, permit
-    /// deduction where the parameter is a function type that can be converted
-    /// to the argument type.
-    TDF_AllowCompatibleFunctionType = 0x20,
-
-    /// Within template argument deduction for a conversion function, we are
-    /// matching with an argument type for which the original argument was
-    /// a reference.
-    TDF_ArgWithReferenceType = 0x40,
-  };
-}
-
-using namespace clang;
-using namespace sema;
-
-/// Compare two APSInts, extending and switching the sign as
-/// necessary to compare their values regardless of underlying type.
-static bool hasSameExtendedValue(llvm::APSInt X, llvm::APSInt Y) {
-  if (Y.getBitWidth() > X.getBitWidth())
-    X = X.extend(Y.getBitWidth());
-  else if (Y.getBitWidth() < X.getBitWidth())
-    Y = Y.extend(X.getBitWidth());
-
-  // If there is a signedness mismatch, correct it.
-  if (X.isSigned() != Y.isSigned()) {
-    // If the signed value is negative, then the values cannot be the same.
-    if ((Y.isSigned() && Y.isNegative()) || (X.isSigned() && X.isNegative()))
-      return false;
-
-    Y.setIsSigned(true);
-    X.setIsSigned(true);
-  }
-
-  return X == Y;
-}
-
-static Sema::TemplateDeductionResult
-DeduceTemplateArguments(Sema &S,
-                        TemplateParameterList *TemplateParams,
-                        const TemplateArgument &Param,
-                        TemplateArgument Arg,
-                        TemplateDeductionInfo &Info,
-                        SmallVectorImpl<DeducedTemplateArgument> &Deduced);
-
-static Sema::TemplateDeductionResult
-DeduceTemplateArgumentsByTypeMatch(Sema &S,
-                                   TemplateParameterList *TemplateParams,
-                                   QualType Param,
-                                   QualType Arg,
-                                   TemplateDeductionInfo &Info,
-                                   SmallVectorImpl<DeducedTemplateArgument> &
-                                                      Deduced,
-                                   unsigned TDF,
-                                   bool PartialOrdering = false,
-                                   bool DeducedFromArrayBound = false);
-
-static Sema::TemplateDeductionResult
-DeduceTemplateArguments(Sema &S, TemplateParameterList *TemplateParams,
-                        ArrayRef<TemplateArgument> Params,
-                        ArrayRef<TemplateArgument> Args,
-                        TemplateDeductionInfo &Info,
-                        SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-                        bool NumberOfArgumentsMustMatch);
-
-static void MarkUsedTemplateParameters(ASTContext &Ctx,
-                                       const TemplateArgument &TemplateArg,
-                                       bool OnlyDeduced, unsigned Depth,
-                                       llvm::SmallBitVector &Used);
-
-static void MarkUsedTemplateParameters(ASTContext &Ctx, QualType T,
-                                       bool OnlyDeduced, unsigned Level,
-                                       llvm::SmallBitVector &Deduced);
-
-/// If the given expression is of a form that permits the deduction
-/// of a non-type template parameter, return the declaration of that
-/// non-type template parameter.
-static NonTypeTemplateParmDecl *
-getDeducedParameterFromExpr(TemplateDeductionInfo &Info, Expr *E) {
-  // If we are within an alias template, the expression may have undergone
-  // any number of parameter substitutions already.
-  while (true) {
-    if (ImplicitCastExpr *IC = dyn_cast<ImplicitCastExpr>(E))
-      E = IC->getSubExpr();
-    else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(E))
-      E = CE->getSubExpr();
-    else if (SubstNonTypeTemplateParmExpr *Subst =
-               dyn_cast<SubstNonTypeTemplateParmExpr>(E))
-      E = Subst->getReplacement();
-    else
-      break;
-  }
-
-  if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
-    if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(DRE->getDecl()))
-      if (NTTP->getDepth() == Info.getDeducedDepth())
-        return NTTP;
-
-  return nullptr;
-}
-
-/// Determine whether two declaration pointers refer to the same
-/// declaration.
-static bool isSameDeclaration(Decl *X, Decl *Y) {
-  if (NamedDecl *NX = dyn_cast<NamedDecl>(X))
-    X = NX->getUnderlyingDecl();
-  if (NamedDecl *NY = dyn_cast<NamedDecl>(Y))
-    Y = NY->getUnderlyingDecl();
-
-  return X->getCanonicalDecl() == Y->getCanonicalDecl();
-}
-
-/// Verify that the given, deduced template arguments are compatible.
-///
-/// \returns The deduced template argument, or a NULL template argument if
-/// the deduced template arguments were incompatible.
-static DeducedTemplateArgument
-checkDeducedTemplateArguments(ASTContext &Context,
-                              const DeducedTemplateArgument &X,
-                              const DeducedTemplateArgument &Y) {
-  // We have no deduction for one or both of the arguments; they're compatible.
-  if (X.isNull())
-    return Y;
-  if (Y.isNull())
-    return X;
-
-  // If we have two non-type template argument values deduced for the same
-  // parameter, they must both match the type of the parameter, and thus must
-  // match each other's type. As we're only keeping one of them, we must check
-  // for that now. The exception is that if either was deduced from an array
-  // bound, the type is permitted to differ.
-  if (!X.wasDeducedFromArrayBound() && !Y.wasDeducedFromArrayBound()) {
-    QualType XType = X.getNonTypeTemplateArgumentType();
-    if (!XType.isNull()) {
-      QualType YType = Y.getNonTypeTemplateArgumentType();
-      if (YType.isNull() || !Context.hasSameType(XType, YType))
-        return DeducedTemplateArgument();
-    }
-  }
-
-  switch (X.getKind()) {
-  case TemplateArgument::Null:
-    llvm_unreachable("Non-deduced template arguments handled above");
-
-  case TemplateArgument::Type:
-    // If two template type arguments have the same type, they're compatible.
-    if (Y.getKind() == TemplateArgument::Type &&
-        Context.hasSameType(X.getAsType(), Y.getAsType()))
-      return X;
-
-    // If one of the two arguments was deduced from an array bound, the other
-    // supersedes it.
-    if (X.wasDeducedFromArrayBound() != Y.wasDeducedFromArrayBound())
-      return X.wasDeducedFromArrayBound() ? Y : X;
-
-    // The arguments are not compatible.
-    return DeducedTemplateArgument();
-
-  case TemplateArgument::Integral:
-    // If we deduced a constant in one case and either a dependent expression or
-    // declaration in another case, keep the integral constant.
-    // If both are integral constants with the same value, keep that value.
-    if (Y.getKind() == TemplateArgument::Expression ||
-        Y.getKind() == TemplateArgument::Declaration ||
-        (Y.getKind() == TemplateArgument::Integral &&
-         hasSameExtendedValue(X.getAsIntegral(), Y.getAsIntegral())))
-      return X.wasDeducedFromArrayBound() ? Y : X;
-
-    // All other combinations are incompatible.
-    return DeducedTemplateArgument();
-
-  case TemplateArgument::Template:
-    if (Y.getKind() == TemplateArgument::Template &&
-        Context.hasSameTemplateName(X.getAsTemplate(), Y.getAsTemplate()))
-      return X;
-
-    // All other combinations are incompatible.
-    return DeducedTemplateArgument();
-
-  case TemplateArgument::TemplateExpansion:
-    if (Y.getKind() == TemplateArgument::TemplateExpansion &&
-        Context.hasSameTemplateName(X.getAsTemplateOrTemplatePattern(),
-                                    Y.getAsTemplateOrTemplatePattern()))
-      return X;
-
-    // All other combinations are incompatible.
-    return DeducedTemplateArgument();
-
-  case TemplateArgument::Expression: {
-    if (Y.getKind() != TemplateArgument::Expression)
-      return checkDeducedTemplateArguments(Context, Y, X);
-
-    // Compare the expressions for equality
-    llvm::FoldingSetNodeID ID1, ID2;
-    X.getAsExpr()->Profile(ID1, Context, true);
-    Y.getAsExpr()->Profile(ID2, Context, true);
-    if (ID1 == ID2)
-      return X.wasDeducedFromArrayBound() ? Y : X;
-
-    // Differing dependent expressions are incompatible.
-    return DeducedTemplateArgument();
-  }
-
-  case TemplateArgument::Declaration:
-    assert(!X.wasDeducedFromArrayBound());
-
-    // If we deduced a declaration and a dependent expression, keep the
-    // declaration.
-    if (Y.getKind() == TemplateArgument::Expression)
-      return X;
-
-    // If we deduced a declaration and an integral constant, keep the
-    // integral constant and whichever type did not come from an array
-    // bound.
-    if (Y.getKind() == TemplateArgument::Integral) {
-      if (Y.wasDeducedFromArrayBound())
-        return TemplateArgument(Context, Y.getAsIntegral(),
-                                X.getParamTypeForDecl());
-      return Y;
-    }
-
-    // If we deduced two declarations, make sure that they refer to the
-    // same declaration.
-    if (Y.getKind() == TemplateArgument::Declaration &&
-        isSameDeclaration(X.getAsDecl(), Y.getAsDecl()))
-      return X;
-
-    // All other combinations are incompatible.
-    return DeducedTemplateArgument();
-
-  case TemplateArgument::NullPtr:
-    // If we deduced a null pointer and a dependent expression, keep the
-    // null pointer.
-    if (Y.getKind() == TemplateArgument::Expression)
-      return X;
-
-    // If we deduced a null pointer and an integral constant, keep the
-    // integral constant.
-    if (Y.getKind() == TemplateArgument::Integral)
-      return Y;
-
-    // If we deduced two null pointers, they are the same.
-    if (Y.getKind() == TemplateArgument::NullPtr)
-      return X;
-
-    // All other combinations are incompatible.
-    return DeducedTemplateArgument();
-
-  case TemplateArgument::Pack: {
-    if (Y.getKind() != TemplateArgument::Pack ||
-        X.pack_size() != Y.pack_size())
-      return DeducedTemplateArgument();
-
-    llvm::SmallVector<TemplateArgument, 8> NewPack;
-    for (TemplateArgument::pack_iterator XA = X.pack_begin(),
-                                      XAEnd = X.pack_end(),
-                                         YA = Y.pack_begin();
-         XA != XAEnd; ++XA, ++YA) {
-      TemplateArgument Merged = checkDeducedTemplateArguments(
-          Context, DeducedTemplateArgument(*XA, X.wasDeducedFromArrayBound()),
-          DeducedTemplateArgument(*YA, Y.wasDeducedFromArrayBound()));
-      if (Merged.isNull())
-        return DeducedTemplateArgument();
-      NewPack.push_back(Merged);
-    }
-
-    return DeducedTemplateArgument(
-        TemplateArgument::CreatePackCopy(Context, NewPack),
-        X.wasDeducedFromArrayBound() && Y.wasDeducedFromArrayBound());
-  }
-  }
-
-  llvm_unreachable("Invalid TemplateArgument Kind!");
-}
-
-/// Deduce the value of the given non-type template parameter
-/// as the given deduced template argument. All non-type template parameter
-/// deduction is funneled through here.
-static Sema::TemplateDeductionResult DeduceNonTypeTemplateArgument(
-    Sema &S, TemplateParameterList *TemplateParams,
-    NonTypeTemplateParmDecl *NTTP, const DeducedTemplateArgument &NewDeduced,
-    QualType ValueType, TemplateDeductionInfo &Info,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
-  assert(NTTP->getDepth() == Info.getDeducedDepth() &&
-         "deducing non-type template argument with wrong depth");
-
-  DeducedTemplateArgument Result = checkDeducedTemplateArguments(
-      S.Context, Deduced[NTTP->getIndex()], NewDeduced);
-  if (Result.isNull()) {
-    Info.Param = NTTP;
-    Info.FirstArg = Deduced[NTTP->getIndex()];
-    Info.SecondArg = NewDeduced;
-    return Sema::TDK_Inconsistent;
-  }
-
-  Deduced[NTTP->getIndex()] = Result;
-  if (!S.getLangOpts().CPlusPlus17)
-    return Sema::TDK_Success;
-
-  if (NTTP->isExpandedParameterPack())
-    // FIXME: We may still need to deduce parts of the type here! But we
-    // don't have any way to find which slice of the type to use, and the
-    // type stored on the NTTP itself is nonsense. Perhaps the type of an
-    // expanded NTTP should be a pack expansion type?
-    return Sema::TDK_Success;
-
-  // Get the type of the parameter for deduction. If it's a (dependent) array
-  // or function type, we will not have decayed it yet, so do that now.
-  QualType ParamType = S.Context.getAdjustedParameterType(NTTP->getType());
-  if (auto *Expansion = dyn_cast<PackExpansionType>(ParamType))
-    ParamType = Expansion->getPattern();
-
-  // FIXME: It's not clear how deduction of a parameter of reference
-  // type from an argument (of non-reference type) should be performed.
-  // For now, we just remove reference types from both sides and let
-  // the final check for matching types sort out the mess.
-  return DeduceTemplateArgumentsByTypeMatch(
-      S, TemplateParams, ParamType.getNonReferenceType(),
-      ValueType.getNonReferenceType(), Info, Deduced, TDF_SkipNonDependent,
-      /*PartialOrdering=*/false,
-      /*ArrayBound=*/NewDeduced.wasDeducedFromArrayBound());
-}
-
-/// Deduce the value of the given non-type template parameter
-/// from the given integral constant.
-static Sema::TemplateDeductionResult DeduceNonTypeTemplateArgument(
-    Sema &S, TemplateParameterList *TemplateParams,
-    NonTypeTemplateParmDecl *NTTP, const llvm::APSInt &Value,
-    QualType ValueType, bool DeducedFromArrayBound, TemplateDeductionInfo &Info,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
-  return DeduceNonTypeTemplateArgument(
-      S, TemplateParams, NTTP,
-      DeducedTemplateArgument(S.Context, Value, ValueType,
-                              DeducedFromArrayBound),
-      ValueType, Info, Deduced);
-}
-
-/// Deduce the value of the given non-type template parameter
-/// from the given null pointer template argument type.
-static Sema::TemplateDeductionResult DeduceNullPtrTemplateArgument(
-    Sema &S, TemplateParameterList *TemplateParams,
-    NonTypeTemplateParmDecl *NTTP, QualType NullPtrType,
-    TemplateDeductionInfo &Info,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
-  Expr *Value =
-      S.ImpCastExprToType(new (S.Context) CXXNullPtrLiteralExpr(
-                              S.Context.NullPtrTy, NTTP->getLocation()),
-                          NullPtrType, CK_NullToPointer)
-          .get();
-  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
-                                       DeducedTemplateArgument(Value),
-                                       Value->getType(), Info, Deduced);
-}
-
-/// Deduce the value of the given non-type template parameter
-/// from the given type- or value-dependent expression.
-///
-/// \returns true if deduction succeeded, false otherwise.
-static Sema::TemplateDeductionResult DeduceNonTypeTemplateArgument(
-    Sema &S, TemplateParameterList *TemplateParams,
-    NonTypeTemplateParmDecl *NTTP, Expr *Value, TemplateDeductionInfo &Info,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
-  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
-                                       DeducedTemplateArgument(Value),
-                                       Value->getType(), Info, Deduced);
-}
-
-/// Deduce the value of the given non-type template parameter
-/// from the given declaration.
-///
-/// \returns true if deduction succeeded, false otherwise.
-static Sema::TemplateDeductionResult DeduceNonTypeTemplateArgument(
-    Sema &S, TemplateParameterList *TemplateParams,
-    NonTypeTemplateParmDecl *NTTP, ValueDecl *D, QualType T,
-    TemplateDeductionInfo &Info,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
-  D = D ? cast<ValueDecl>(D->getCanonicalDecl()) : nullptr;
-  TemplateArgument New(D, T);
-  return DeduceNonTypeTemplateArgument(
-      S, TemplateParams, NTTP, DeducedTemplateArgument(New), T, Info, Deduced);
-}
-
-static Sema::TemplateDeductionResult
-DeduceTemplateArguments(Sema &S,
-                        TemplateParameterList *TemplateParams,
-                        TemplateName Param,
-                        TemplateName Arg,
-                        TemplateDeductionInfo &Info,
-                        SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
-  TemplateDecl *ParamDecl = Param.getAsTemplateDecl();
-  if (!ParamDecl) {
-    // The parameter type is dependent and is not a template template parameter,
-    // so there is nothing that we can deduce.
-    return Sema::TDK_Success;
-  }
-
-  if (TemplateTemplateParmDecl *TempParam
-        = dyn_cast<TemplateTemplateParmDecl>(ParamDecl)) {
-    // If we're not deducing at this depth, there's nothing to deduce.
-    if (TempParam->getDepth() != Info.getDeducedDepth())
-      return Sema::TDK_Success;
-
-    DeducedTemplateArgument NewDeduced(S.Context.getCanonicalTemplateName(Arg));
-    DeducedTemplateArgument Result = checkDeducedTemplateArguments(S.Context,
-                                                 Deduced[TempParam->getIndex()],
-                                                                   NewDeduced);
-    if (Result.isNull()) {
-      Info.Param = TempParam;
-      Info.FirstArg = Deduced[TempParam->getIndex()];
-      Info.SecondArg = NewDeduced;
-      return Sema::TDK_Inconsistent;
-    }
-
-    Deduced[TempParam->getIndex()] = Result;
-    return Sema::TDK_Success;
-  }
-
-  // Verify that the two template names are equivalent.
-  if (S.Context.hasSameTemplateName(Param, Arg))
-    return Sema::TDK_Success;
-
-  // Mismatch of non-dependent template parameter to argument.
-  Info.FirstArg = TemplateArgument(Param);
-  Info.SecondArg = TemplateArgument(Arg);
-  return Sema::TDK_NonDeducedMismatch;
-}
-
-/// Deduce the template arguments by comparing the template parameter
-/// type (which is a template-id) with the template argument type.
-///
-/// \param S the Sema
-///
-/// \param TemplateParams the template parameters that we are deducing
-///
-/// \param Param the parameter type
-///
-/// \param Arg the argument type
-///
-/// \param Info information about the template argument deduction itself
-///
-/// \param Deduced the deduced template arguments
-///
-/// \returns the result of template argument deduction so far. Note that a
-/// "success" result means that template argument deduction has not yet failed,
-/// but it may still fail, later, for other reasons.
-static Sema::TemplateDeductionResult
-DeduceTemplateArguments(Sema &S,
-                        TemplateParameterList *TemplateParams,
-                        const TemplateSpecializationType *Param,
-                        QualType Arg,
-                        TemplateDeductionInfo &Info,
-                        SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
-  assert(Arg.isCanonical() && "Argument type must be canonical");
-
-  // Treat an injected-class-name as its underlying template-id.
-  if (auto *Injected = dyn_cast<InjectedClassNameType>(Arg))
-    Arg = Injected->getInjectedSpecializationType();
-
-  // Check whether the template argument is a dependent template-id.
-  if (const TemplateSpecializationType *SpecArg
-        = dyn_cast<TemplateSpecializationType>(Arg)) {
-    // Perform template argument deduction for the template name.
-    if (Sema::TemplateDeductionResult Result
-          = DeduceTemplateArguments(S, TemplateParams,
-                                    Param->getTemplateName(),
-                                    SpecArg->getTemplateName(),
-                                    Info, Deduced))
-      return Result;
-
-
-    // Perform template argument deduction on each template
-    // argument. Ignore any missing/extra arguments, since they could be
-    // filled in by default arguments.
-    return DeduceTemplateArguments(S, TemplateParams,
-                                   Param->template_arguments(),
-                                   SpecArg->template_arguments(), Info, Deduced,
-                                   /*NumberOfArgumentsMustMatch=*/false);
-  }
-
-  // If the argument type is a class template specialization, we
-  // perform template argument deduction using its template
-  // arguments.
-  const RecordType *RecordArg = dyn_cast<RecordType>(Arg);
-  if (!RecordArg) {
-    Info.FirstArg = TemplateArgument(QualType(Param, 0));
-    Info.SecondArg = TemplateArgument(Arg);
-    return Sema::TDK_NonDeducedMismatch;
-  }
-
-  ClassTemplateSpecializationDecl *SpecArg
-    = dyn_cast<ClassTemplateSpecializationDecl>(RecordArg->getDecl());
-  if (!SpecArg) {
-    Info.FirstArg = TemplateArgument(QualType(Param, 0));
-    Info.SecondArg = TemplateArgument(Arg);
-    return Sema::TDK_NonDeducedMismatch;
-  }
-
-  // Perform template argument deduction for the template name.
-  if (Sema::TemplateDeductionResult Result
-        = DeduceTemplateArguments(S,
-                                  TemplateParams,
-                                  Param->getTemplateName(),
-                               TemplateName(SpecArg->getSpecializedTemplate()),
-                                  Info, Deduced))
-    return Result;
-
-  // Perform template argument deduction for the template arguments.
-  return DeduceTemplateArguments(S, TemplateParams, Param->template_arguments(),
-                                 SpecArg->getTemplateArgs().asArray(), Info,
-                                 Deduced, /*NumberOfArgumentsMustMatch=*/true);
-}
-
-/// Determines whether the given type is an opaque type that
-/// might be more qualified when instantiated.
-static bool IsPossiblyOpaquelyQualifiedType(QualType T) {
-  switch (T->getTypeClass()) {
-  case Type::TypeOfExpr:
-  case Type::TypeOf:
-  case Type::DependentName:
-  case Type::Decltype:
-  case Type::UnresolvedUsing:
-  case Type::TemplateTypeParm:
-    return true;
-
-  case Type::ConstantArray:
-  case Type::IncompleteArray:
-  case Type::VariableArray:
-  case Type::DependentSizedArray:
-    return IsPossiblyOpaquelyQualifiedType(
-                                      cast<ArrayType>(T)->getElementType());
-
-  default:
-    return false;
-  }
-}
-
-/// Helper function to build a TemplateParameter when we don't
-/// know its type statically.
-static TemplateParameter makeTemplateParameter(Decl *D) {
-  if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(D))
-    return TemplateParameter(TTP);
-  if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D))
-    return TemplateParameter(NTTP);
-
-  return TemplateParameter(cast<TemplateTemplateParmDecl>(D));
-}
-
-/// If \p Param is an expanded parameter pack, get the number of expansions.
-static Optional<unsigned> getExpandedPackSize(NamedDecl *Param) {
-  if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param))
-    if (NTTP->isExpandedParameterPack())
-      return NTTP->getNumExpansionTypes();
-
-  if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(Param))
-    if (TTP->isExpandedParameterPack())
-      return TTP->getNumExpansionTemplateParameters();
-
-  return None;
-}
-
-/// A pack that we're currently deducing.
-struct clang::DeducedPack {
-  // The index of the pack.
-  unsigned Index;
-
-  // The old value of the pack before we started deducing it.
-  DeducedTemplateArgument Saved;
-
-  // A deferred value of this pack from an inner deduction, that couldn't be
-  // deduced because this deduction hadn't happened yet.
-  DeducedTemplateArgument DeferredDeduction;
-
-  // The new value of the pack.
-  SmallVector<DeducedTemplateArgument, 4> New;
-
-  // The outer deduction for this pack, if any.
-  DeducedPack *Outer = nullptr;
-
-  DeducedPack(unsigned Index) : Index(Index) {}
-};
-
-namespace {
-
-/// A scope in which we're performing pack deduction.
-class PackDeductionScope {
-public:
-  /// Prepare to deduce the packs named within Pattern.
-  PackDeductionScope(Sema &S, TemplateParameterList *TemplateParams,
-                     SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-                     TemplateDeductionInfo &Info, TemplateArgument Pattern)
-      : S(S), TemplateParams(TemplateParams), Deduced(Deduced), Info(Info) {
-    unsigned NumNamedPacks = addPacks(Pattern);
-    finishConstruction(NumNamedPacks);
-  }
-
-  /// Prepare to directly deduce arguments of the parameter with index \p Index.
-  PackDeductionScope(Sema &S, TemplateParameterList *TemplateParams,
-                     SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-                     TemplateDeductionInfo &Info, unsigned Index)
-      : S(S), TemplateParams(TemplateParams), Deduced(Deduced), Info(Info) {
-    addPack(Index);
-    finishConstruction(1);
-  }
-
-private:
-  void addPack(unsigned Index) {
-    // Save the deduced template argument for the parameter pack expanded
-    // by this pack expansion, then clear out the deduction.
-    DeducedPack Pack(Index);
-    Pack.Saved = Deduced[Index];
-    Deduced[Index] = TemplateArgument();
-
-    // FIXME: What if we encounter multiple packs with different numbers of
-    // pre-expanded expansions? (This should already have been diagnosed
-    // during substitution.)
-    if (Optional<unsigned> ExpandedPackExpansions =
-            getExpandedPackSize(TemplateParams->getParam(Index)))
-      FixedNumExpansions = ExpandedPackExpansions;
-
-    Packs.push_back(Pack);
-  }
-
-  unsigned addPacks(TemplateArgument Pattern) {
-    // Compute the set of template parameter indices that correspond to
-    // parameter packs expanded by the pack expansion.
-    llvm::SmallBitVector SawIndices(TemplateParams->size());
-
-    auto AddPack = [&](unsigned Index) {
-      if (SawIndices[Index])
-        return;
-      SawIndices[Index] = true;
-      addPack(Index);
-    };
-
-    // First look for unexpanded packs in the pattern.
-    SmallVector<UnexpandedParameterPack, 2> Unexpanded;
-    S.collectUnexpandedParameterPacks(Pattern, Unexpanded);
-    for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
-      unsigned Depth, Index;
-      std::tie(Depth, Index) = getDepthAndIndex(Unexpanded[I]);
-      if (Depth == Info.getDeducedDepth())
-        AddPack(Index);
-    }
-    assert(!Packs.empty() && "Pack expansion without unexpanded packs?");
-
-    unsigned NumNamedPacks = Packs.size();
-
-    // We can also have deduced template parameters that do not actually
-    // appear in the pattern, but can be deduced by it (the type of a non-type
-    // template parameter pack, in particular). These won't have prevented us
-    // from partially expanding the pack.
-    llvm::SmallBitVector Used(TemplateParams->size());
-    MarkUsedTemplateParameters(S.Context, Pattern, /*OnlyDeduced*/true,
-                               Info.getDeducedDepth(), Used);
-    for (int Index = Used.find_first(); Index != -1;
-         Index = Used.find_next(Index))
-      if (TemplateParams->getParam(Index)->isParameterPack())
-        AddPack(Index);
-
-    return NumNamedPacks;
-  }
-
-  void finishConstruction(unsigned NumNamedPacks) {
-    // Dig out the partially-substituted pack, if there is one.
-    const TemplateArgument *PartialPackArgs = nullptr;
-    unsigned NumPartialPackArgs = 0;
-    std::pair<unsigned, unsigned> PartialPackDepthIndex(-1u, -1u);
-    if (auto *Scope = S.CurrentInstantiationScope)
-      if (auto *Partial = Scope->getPartiallySubstitutedPack(
-              &PartialPackArgs, &NumPartialPackArgs))
-        PartialPackDepthIndex = getDepthAndIndex(Partial);
-
-    // This pack expansion will have been partially or fully expanded if
-    // it only names explicitly-specified parameter packs (including the
-    // partially-substituted one, if any).
-    bool IsExpanded = true;
-    for (unsigned I = 0; I != NumNamedPacks; ++I) {
-      if (Packs[I].Index >= Info.getNumExplicitArgs()) {
-        IsExpanded = false;
-        IsPartiallyExpanded = false;
-        break;
-      }
-      if (PartialPackDepthIndex ==
-            std::make_pair(Info.getDeducedDepth(), Packs[I].Index)) {
-        IsPartiallyExpanded = true;
-      }
-    }
-
-    // Skip over the pack elements that were expanded into separate arguments.
-    // If we partially expanded, this is the number of partial arguments.
-    if (IsPartiallyExpanded)
-      PackElements += NumPartialPackArgs;
-    else if (IsExpanded)
-      PackElements += *FixedNumExpansions;
-
-    for (auto &Pack : Packs) {
-      if (Info.PendingDeducedPacks.size() > Pack.Index)
-        Pack.Outer = Info.PendingDeducedPacks[Pack.Index];
-      else
-        Info.PendingDeducedPacks.resize(Pack.Index + 1);
-      Info.PendingDeducedPacks[Pack.Index] = &Pack;
-
-      if (PartialPackDepthIndex ==
-            std::make_pair(Info.getDeducedDepth(), Pack.Index)) {
-        Pack.New.append(PartialPackArgs, PartialPackArgs + NumPartialPackArgs);
-        // We pre-populate the deduced value of the partially-substituted
-        // pack with the specified value. This is not entirely correct: the
-        // value is supposed to have been substituted, not deduced, but the
-        // cases where this is observable require an exact type match anyway.
-        //
-        // FIXME: If we could represent a "depth i, index j, pack elem k"
-        // parameter, we could substitute the partially-substituted pack
-        // everywhere and avoid this.
-        if (!IsPartiallyExpanded)
-          Deduced[Pack.Index] = Pack.New[PackElements];
-      }
-    }
-  }
-
-public:
-  ~PackDeductionScope() {
-    for (auto &Pack : Packs)
-      Info.PendingDeducedPacks[Pack.Index] = Pack.Outer;
-  }
-
-  /// Determine whether this pack has already been partially expanded into a
-  /// sequence of (prior) function parameters / template arguments.
-  bool isPartiallyExpanded() { return IsPartiallyExpanded; }
-
-  /// Determine whether this pack expansion scope has a known, fixed arity.
-  /// This happens if it involves a pack from an outer template that has
-  /// (notionally) already been expanded.
-  bool hasFixedArity() { return FixedNumExpansions.hasValue(); }
-
-  /// Determine whether the next element of the argument is still part of this
-  /// pack. This is the case unless the pack is already expanded to a fixed
-  /// length.
-  bool hasNextElement() {
-    return !FixedNumExpansions || *FixedNumExpansions > PackElements;
-  }
-
-  /// Move to deducing the next element in each pack that is being deduced.
-  void nextPackElement() {
-    // Capture the deduced template arguments for each parameter pack expanded
-    // by this pack expansion, add them to the list of arguments we've deduced
-    // for that pack, then clear out the deduced argument.
-    for (auto &Pack : Packs) {
-      DeducedTemplateArgument &DeducedArg = Deduced[Pack.Index];
-      if (!Pack.New.empty() || !DeducedArg.isNull()) {
-        while (Pack.New.size() < PackElements)
-          Pack.New.push_back(DeducedTemplateArgument());
-        if (Pack.New.size() == PackElements)
-          Pack.New.push_back(DeducedArg);
-        else
-          Pack.New[PackElements] = DeducedArg;
-        DeducedArg = Pack.New.size() > PackElements + 1
-                         ? Pack.New[PackElements + 1]
-                         : DeducedTemplateArgument();
-      }
-    }
-    ++PackElements;
-  }
-
-  /// Finish template argument deduction for a set of argument packs,
-  /// producing the argument packs and checking for consistency with prior
-  /// deductions.
-  Sema::TemplateDeductionResult
-  finish(bool TreatNoDeductionsAsNonDeduced = true) {
-    // Build argument packs for each of the parameter packs expanded by this
-    // pack expansion.
-    for (auto &Pack : Packs) {
-      // Put back the old value for this pack.
-      Deduced[Pack.Index] = Pack.Saved;
-
-      // If we are deducing the size of this pack even if we didn't deduce any
-      // values for it, then make sure we build a pack of the right size.
-      // FIXME: Should we always deduce the size, even if the pack appears in
-      // a non-deduced context?
-      if (!TreatNoDeductionsAsNonDeduced)
-        Pack.New.resize(PackElements);
-
-      // Build or find a new value for this pack.
-      DeducedTemplateArgument NewPack;
-      if (PackElements && Pack.New.empty()) {
-        if (Pack.DeferredDeduction.isNull()) {
-          // We were not able to deduce anything for this parameter pack
-          // (because it only appeared in non-deduced contexts), so just
-          // restore the saved argument pack.
-          continue;
-        }
-
-        NewPack = Pack.DeferredDeduction;
-        Pack.DeferredDeduction = TemplateArgument();
-      } else if (Pack.New.empty()) {
-        // If we deduced an empty argument pack, create it now.
-        NewPack = DeducedTemplateArgument(TemplateArgument::getEmptyPack());
-      } else {
-        TemplateArgument *ArgumentPack =
-            new (S.Context) TemplateArgument[Pack.New.size()];
-        std::copy(Pack.New.begin(), Pack.New.end(), ArgumentPack);
-        NewPack = DeducedTemplateArgument(
-            TemplateArgument(llvm::makeArrayRef(ArgumentPack, Pack.New.size())),
-            // FIXME: This is wrong, it's possible that some pack elements are
-            // deduced from an array bound and others are not:
-            //   template<typename ...T, T ...V> void g(const T (&...p)[V]);
-            //   g({1, 2, 3}, {{}, {}});
-            // ... should deduce T = {int, size_t (from array bound)}.
-            Pack.New[0].wasDeducedFromArrayBound());
-      }
-
-      // Pick where we're going to put the merged pack.
-      DeducedTemplateArgument *Loc;
-      if (Pack.Outer) {
-        if (Pack.Outer->DeferredDeduction.isNull()) {
-          // Defer checking this pack until we have a complete pack to compare
-          // it against.
-          Pack.Outer->DeferredDeduction = NewPack;
-          continue;
-        }
-        Loc = &Pack.Outer->DeferredDeduction;
-      } else {
-        Loc = &Deduced[Pack.Index];
-      }
-
-      // Check the new pack matches any previous value.
-      DeducedTemplateArgument OldPack = *Loc;
-      DeducedTemplateArgument Result =
-          checkDeducedTemplateArguments(S.Context, OldPack, NewPack);
-
-      // If we deferred a deduction of this pack, check that one now too.
-      if (!Result.isNull() && !Pack.DeferredDeduction.isNull()) {
-        OldPack = Result;
-        NewPack = Pack.DeferredDeduction;
-        Result = checkDeducedTemplateArguments(S.Context, OldPack, NewPack);
-      }
-
-      NamedDecl *Param = TemplateParams->getParam(Pack.Index);
-      if (Result.isNull()) {
-        Info.Param = makeTemplateParameter(Param);
-        Info.FirstArg = OldPack;
-        Info.SecondArg = NewPack;
-        return Sema::TDK_Inconsistent;
-      }
-
-      // If we have a pre-expanded pack and we didn't deduce enough elements
-      // for it, fail deduction.
-      if (Optional<unsigned> Expansions = getExpandedPackSize(Param)) {
-        if (*Expansions != PackElements) {
-          Info.Param = makeTemplateParameter(Param);
-          Info.FirstArg = Result;
-          return Sema::TDK_IncompletePack;
-        }
-      }
-
-      *Loc = Result;
-    }
-
-    return Sema::TDK_Success;
-  }
-
-private:
-  Sema &S;
-  TemplateParameterList *TemplateParams;
-  SmallVectorImpl<DeducedTemplateArgument> &Deduced;
-  TemplateDeductionInfo &Info;
-  unsigned PackElements = 0;
-  bool IsPartiallyExpanded = false;
-  /// The number of expansions, if we have a fully-expanded pack in this scope.
-  Optional<unsigned> FixedNumExpansions;
-
-  SmallVector<DeducedPack, 2> Packs;
-};
-
-} // namespace
-
-/// Deduce the template arguments by comparing the list of parameter
-/// types to the list of argument types, as in the parameter-type-lists of
-/// function types (C++ [temp.deduct.type]p10).
-///
-/// \param S The semantic analysis object within which we are deducing
-///
-/// \param TemplateParams The template parameters that we are deducing
-///
-/// \param Params The list of parameter types
-///
-/// \param NumParams The number of types in \c Params
-///
-/// \param Args The list of argument types
-///
-/// \param NumArgs The number of types in \c Args
-///
-/// \param Info information about the template argument deduction itself
-///
-/// \param Deduced the deduced template arguments
-///
-/// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
-/// how template argument deduction is performed.
-///
-/// \param PartialOrdering If true, we are performing template argument
-/// deduction for during partial ordering for a call
-/// (C++0x [temp.deduct.partial]).
-///
-/// \returns the result of template argument deduction so far. Note that a
-/// "success" result means that template argument deduction has not yet failed,
-/// but it may still fail, later, for other reasons.
-static Sema::TemplateDeductionResult
-DeduceTemplateArguments(Sema &S,
-                        TemplateParameterList *TemplateParams,
-                        const QualType *Params, unsigned NumParams,
-                        const QualType *Args, unsigned NumArgs,
-                        TemplateDeductionInfo &Info,
-                        SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-                        unsigned TDF,
-                        bool PartialOrdering = false) {
-  // C++0x [temp.deduct.type]p10:
-  //   Similarly, if P has a form that contains (T), then each parameter type
-  //   Pi of the respective parameter-type- list of P is compared with the
-  //   corresponding parameter type Ai of the corresponding parameter-type-list
-  //   of A. [...]
-  unsigned ArgIdx = 0, ParamIdx = 0;
-  for (; ParamIdx != NumParams; ++ParamIdx) {
-    // Check argument types.
-    const PackExpansionType *Expansion
-                                = dyn_cast<PackExpansionType>(Params[ParamIdx]);
-    if (!Expansion) {
-      // Simple case: compare the parameter and argument types at this point.
-
-      // Make sure we have an argument.
-      if (ArgIdx >= NumArgs)
-        return Sema::TDK_MiscellaneousDeductionFailure;
-
-      if (isa<PackExpansionType>(Args[ArgIdx])) {
-        // C++0x [temp.deduct.type]p22:
-        //   If the original function parameter associated with A is a function
-        //   parameter pack and the function parameter associated with P is not
-        //   a function parameter pack, then template argument deduction fails.
-        return Sema::TDK_MiscellaneousDeductionFailure;
-      }
-
-      if (Sema::TemplateDeductionResult Result
-            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                                 Params[ParamIdx], Args[ArgIdx],
-                                                 Info, Deduced, TDF,
-                                                 PartialOrdering))
-        return Result;
-
-      ++ArgIdx;
-      continue;
-    }
-
-    // C++0x [temp.deduct.type]p10:
-    //   If the parameter-declaration corresponding to Pi is a function
-    //   parameter pack, then the type of its declarator- id is compared with
-    //   each remaining parameter type in the parameter-type-list of A. Each
-    //   comparison deduces template arguments for subsequent positions in the
-    //   template parameter packs expanded by the function parameter pack.
-
-    QualType Pattern = Expansion->getPattern();
-    PackDeductionScope PackScope(S, TemplateParams, Deduced, Info, Pattern);
-
-    // A pack scope with fixed arity is not really a pack any more, so is not
-    // a non-deduced context.
-    if (ParamIdx + 1 == NumParams || PackScope.hasFixedArity()) {
-      for (; ArgIdx < NumArgs && PackScope.hasNextElement(); ++ArgIdx) {
-        // Deduce template arguments from the pattern.
-        if (Sema::TemplateDeductionResult Result
-              = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, Pattern,
-                                                   Args[ArgIdx], Info, Deduced,
-                                                   TDF, PartialOrdering))
-          return Result;
-
-        PackScope.nextPackElement();
-      }
-    } else {
-      // C++0x [temp.deduct.type]p5:
-      //   The non-deduced contexts are:
-      //     - A function parameter pack that does not occur at the end of the
-      //       parameter-declaration-clause.
-      //
-      // FIXME: There is no wording to say what we should do in this case. We
-      // choose to resolve this by applying the same rule that is applied for a
-      // function call: that is, deduce all contained packs to their
-      // explicitly-specified values (or to <> if there is no such value).
-      //
-      // This is seemingly-arbitrarily different from the case of a template-id
-      // with a non-trailing pack-expansion in its arguments, which renders the
-      // entire template-argument-list a non-deduced context.
-
-      // If the parameter type contains an explicitly-specified pack that we
-      // could not expand, skip the number of parameters notionally created
-      // by the expansion.
-      Optional<unsigned> NumExpansions = Expansion->getNumExpansions();
-      if (NumExpansions && !PackScope.isPartiallyExpanded()) {
-        for (unsigned I = 0; I != *NumExpansions && ArgIdx < NumArgs;
-             ++I, ++ArgIdx)
-          PackScope.nextPackElement();
-      }
-    }
-
-    // Build argument packs for each of the parameter packs expanded by this
-    // pack expansion.
-    if (auto Result = PackScope.finish())
-      return Result;
-  }
-
-  // Make sure we don't have any extra arguments.
-  if (ArgIdx < NumArgs)
-    return Sema::TDK_MiscellaneousDeductionFailure;
-
-  return Sema::TDK_Success;
-}
-
-/// Determine whether the parameter has qualifiers that the argument
-/// lacks. Put another way, determine whether there is no way to add
-/// a deduced set of qualifiers to the ParamType that would result in
-/// its qualifiers matching those of the ArgType.
-static bool hasInconsistentOrSupersetQualifiersOf(QualType ParamType,
-                                                  QualType ArgType) {
-  Qualifiers ParamQs = ParamType.getQualifiers();
-  Qualifiers ArgQs = ArgType.getQualifiers();
-
-  if (ParamQs == ArgQs)
-    return false;
-
-  // Mismatched (but not missing) Objective-C GC attributes.
-  if (ParamQs.getObjCGCAttr() != ArgQs.getObjCGCAttr() &&
-      ParamQs.hasObjCGCAttr())
-    return true;
-
-  // Mismatched (but not missing) address spaces.
-  if (ParamQs.getAddressSpace() != ArgQs.getAddressSpace() &&
-      ParamQs.hasAddressSpace())
-    return true;
-
-  // Mismatched (but not missing) Objective-C lifetime qualifiers.
-  if (ParamQs.getObjCLifetime() != ArgQs.getObjCLifetime() &&
-      ParamQs.hasObjCLifetime())
-    return true;
-
-  // CVR qualifiers inconsistent or a superset.
-  return (ParamQs.getCVRQualifiers() & ~ArgQs.getCVRQualifiers()) != 0;
-}
-
-/// Compare types for equality with respect to possibly compatible
-/// function types (noreturn adjustment, implicit calling conventions). If any
-/// of parameter and argument is not a function, just perform type comparison.
-///
-/// \param Param the template parameter type.
-///
-/// \param Arg the argument type.
-bool Sema::isSameOrCompatibleFunctionType(CanQualType Param,
-                                          CanQualType Arg) {
-  const FunctionType *ParamFunction = Param->getAs<FunctionType>(),
-                     *ArgFunction   = Arg->getAs<FunctionType>();
-
-  // Just compare if not functions.
-  if (!ParamFunction || !ArgFunction)
-    return Param == Arg;
-
-  // Noreturn and noexcept adjustment.
-  QualType AdjustedParam;
-  if (IsFunctionConversion(Param, Arg, AdjustedParam))
-    return Arg == Context.getCanonicalType(AdjustedParam);
-
-  // FIXME: Compatible calling conventions.
-
-  return Param == Arg;
-}
-
-/// Get the index of the first template parameter that was originally from the
-/// innermost template-parameter-list. This is 0 except when we concatenate
-/// the template parameter lists of a class template and a constructor template
-/// when forming an implicit deduction guide.
-static unsigned getFirstInnerIndex(FunctionTemplateDecl *FTD) {
-  auto *Guide = dyn_cast<CXXDeductionGuideDecl>(FTD->getTemplatedDecl());
-  if (!Guide || !Guide->isImplicit())
-    return 0;
-  return Guide->getDeducedTemplate()->getTemplateParameters()->size();
-}
-
-/// Determine whether a type denotes a forwarding reference.
-static bool isForwardingReference(QualType Param, unsigned FirstInnerIndex) {
-  // C++1z [temp.deduct.call]p3:
-  //   A forwarding reference is an rvalue reference to a cv-unqualified
-  //   template parameter that does not represent a template parameter of a
-  //   class template.
-  if (auto *ParamRef = Param->getAs<RValueReferenceType>()) {
-    if (ParamRef->getPointeeType().getQualifiers())
-      return false;
-    auto *TypeParm = ParamRef->getPointeeType()->getAs<TemplateTypeParmType>();
-    return TypeParm && TypeParm->getIndex() >= FirstInnerIndex;
-  }
-  return false;
-}
-
-/// Deduce the template arguments by comparing the parameter type and
-/// the argument type (C++ [temp.deduct.type]).
-///
-/// \param S the semantic analysis object within which we are deducing
-///
-/// \param TemplateParams the template parameters that we are deducing
-///
-/// \param ParamIn the parameter type
-///
-/// \param ArgIn the argument type
-///
-/// \param Info information about the template argument deduction itself
-///
-/// \param Deduced the deduced template arguments
-///
-/// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
-/// how template argument deduction is performed.
-///
-/// \param PartialOrdering Whether we're performing template argument deduction
-/// in the context of partial ordering (C++0x [temp.deduct.partial]).
-///
-/// \returns the result of template argument deduction so far. Note that a
-/// "success" result means that template argument deduction has not yet failed,
-/// but it may still fail, later, for other reasons.
-static Sema::TemplateDeductionResult
-DeduceTemplateArgumentsByTypeMatch(Sema &S,
-                                   TemplateParameterList *TemplateParams,
-                                   QualType ParamIn, QualType ArgIn,
-                                   TemplateDeductionInfo &Info,
-                            SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-                                   unsigned TDF,
-                                   bool PartialOrdering,
-                                   bool DeducedFromArrayBound) {
-  // We only want to look at the canonical types, since typedefs and
-  // sugar are not part of template argument deduction.
-  QualType Param = S.Context.getCanonicalType(ParamIn);
-  QualType Arg = S.Context.getCanonicalType(ArgIn);
-
-  // If the argument type is a pack expansion, look at its pattern.
-  // This isn't explicitly called out
-  if (const PackExpansionType *ArgExpansion
-                                            = dyn_cast<PackExpansionType>(Arg))
-    Arg = ArgExpansion->getPattern();
-
-  if (PartialOrdering) {
-    // C++11 [temp.deduct.partial]p5:
-    //   Before the partial ordering is done, certain transformations are
-    //   performed on the types used for partial ordering:
-    //     - If P is a reference type, P is replaced by the type referred to.
-    const ReferenceType *ParamRef = Param->getAs<ReferenceType>();
-    if (ParamRef)
-      Param = ParamRef->getPointeeType();
-
-    //     - If A is a reference type, A is replaced by the type referred to.
-    const ReferenceType *ArgRef = Arg->getAs<ReferenceType>();
-    if (ArgRef)
-      Arg = ArgRef->getPointeeType();
-
-    if (ParamRef && ArgRef && S.Context.hasSameUnqualifiedType(Param, Arg)) {
-      // C++11 [temp.deduct.partial]p9:
-      //   If, for a given type, deduction succeeds in both directions (i.e.,
-      //   the types are identical after the transformations above) and both
-      //   P and A were reference types [...]:
-      //     - if [one type] was an lvalue reference and [the other type] was
-      //       not, [the other type] is not considered to be at least as
-      //       specialized as [the first type]
-      //     - if [one type] is more cv-qualified than [the other type],
-      //       [the other type] is not considered to be at least as specialized
-      //       as [the first type]
-      // Objective-C ARC adds:
-      //     - [one type] has non-trivial lifetime, [the other type] has
-      //       __unsafe_unretained lifetime, and the types are otherwise
-      //       identical
-      //
-      // A is "considered to be at least as specialized" as P iff deduction
-      // succeeds, so we model this as a deduction failure. Note that
-      // [the first type] is P and [the other type] is A here; the standard
-      // gets this backwards.
-      Qualifiers ParamQuals = Param.getQualifiers();
-      Qualifiers ArgQuals = Arg.getQualifiers();
-      if ((ParamRef->isLValueReferenceType() &&
-           !ArgRef->isLValueReferenceType()) ||
-          ParamQuals.isStrictSupersetOf(ArgQuals) ||
-          (ParamQuals.hasNonTrivialObjCLifetime() &&
-           ArgQuals.getObjCLifetime() == Qualifiers::OCL_ExplicitNone &&
-           ParamQuals.withoutObjCLifetime() ==
-               ArgQuals.withoutObjCLifetime())) {
-        Info.FirstArg = TemplateArgument(ParamIn);
-        Info.SecondArg = TemplateArgument(ArgIn);
-        return Sema::TDK_NonDeducedMismatch;
-      }
-    }
-
-    // C++11 [temp.deduct.partial]p7:
-    //   Remove any top-level cv-qualifiers:
-    //     - If P is a cv-qualified type, P is replaced by the cv-unqualified
-    //       version of P.
-    Param = Param.getUnqualifiedType();
-    //     - If A is a cv-qualified type, A is replaced by the cv-unqualified
-    //       version of A.
-    Arg = Arg.getUnqualifiedType();
-  } else {
-    // C++0x [temp.deduct.call]p4 bullet 1:
-    //   - If the original P is a reference type, the deduced A (i.e., the type
-    //     referred to by the reference) can be more cv-qualified than the
-    //     transformed A.
-    if (TDF & TDF_ParamWithReferenceType) {
-      Qualifiers Quals;
-      QualType UnqualParam = S.Context.getUnqualifiedArrayType(Param, Quals);
-      Quals.setCVRQualifiers(Quals.getCVRQualifiers() &
-                             Arg.getCVRQualifiers());
-      Param = S.Context.getQualifiedType(UnqualParam, Quals);
-    }
-
-    if ((TDF & TDF_TopLevelParameterTypeList) && !Param->isFunctionType()) {
-      // C++0x [temp.deduct.type]p10:
-      //   If P and A are function types that originated from deduction when
-      //   taking the address of a function template (14.8.2.2) or when deducing
-      //   template arguments from a function declaration (14.8.2.6) and Pi and
-      //   Ai are parameters of the top-level parameter-type-list of P and A,
-      //   respectively, Pi is adjusted if it is a forwarding reference and Ai
-      //   is an lvalue reference, in
-      //   which case the type of Pi is changed to be the template parameter
-      //   type (i.e., T&& is changed to simply T). [ Note: As a result, when
-      //   Pi is T&& and Ai is X&, the adjusted Pi will be T, causing T to be
-      //   deduced as X&. - end note ]
-      TDF &= ~TDF_TopLevelParameterTypeList;
-      if (isForwardingReference(Param, 0) && Arg->isLValueReferenceType())
-        Param = Param->getPointeeType();
-    }
-  }
-
-  // C++ [temp.deduct.type]p9:
-  //   A template type argument T, a template template argument TT or a
-  //   template non-type argument i can be deduced if P and A have one of
-  //   the following forms:
-  //
-  //     T
-  //     cv-list T
-  if (const TemplateTypeParmType *TemplateTypeParm
-        = Param->getAs<TemplateTypeParmType>()) {
-    // Just skip any attempts to deduce from a placeholder type or a parameter
-    // at a different depth.
-    if (Arg->isPlaceholderType() ||
-        Info.getDeducedDepth() != TemplateTypeParm->getDepth())
-      return Sema::TDK_Success;
-
-    unsigned Index = TemplateTypeParm->getIndex();
-    bool RecanonicalizeArg = false;
-
-    // If the argument type is an array type, move the qualifiers up to the
-    // top level, so they can be matched with the qualifiers on the parameter.
-    if (isa<ArrayType>(Arg)) {
-      Qualifiers Quals;
-      Arg = S.Context.getUnqualifiedArrayType(Arg, Quals);
-      if (Quals) {
-        Arg = S.Context.getQualifiedType(Arg, Quals);
-        RecanonicalizeArg = true;
-      }
-    }
-
-    // The argument type can not be less qualified than the parameter
-    // type.
-    if (!(TDF & TDF_IgnoreQualifiers) &&
-        hasInconsistentOrSupersetQualifiersOf(Param, Arg)) {
-      Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
-      Info.FirstArg = TemplateArgument(Param);
-      Info.SecondArg = TemplateArgument(Arg);
-      return Sema::TDK_Underqualified;
-    }
-
-    // Do not match a function type with a cv-qualified type.
-    // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1584
-    if (Arg->isFunctionType() && Param.hasQualifiers()) {
-      return Sema::TDK_NonDeducedMismatch;
-    }
-
-    assert(TemplateTypeParm->getDepth() == Info.getDeducedDepth() &&
-           "saw template type parameter with wrong depth");
-    assert(Arg != S.Context.OverloadTy && "Unresolved overloaded function");
-    QualType DeducedType = Arg;
-
-    // Remove any qualifiers on the parameter from the deduced type.
-    // We checked the qualifiers for consistency above.
-    Qualifiers DeducedQs = DeducedType.getQualifiers();
-    Qualifiers ParamQs = Param.getQualifiers();
-    DeducedQs.removeCVRQualifiers(ParamQs.getCVRQualifiers());
-    if (ParamQs.hasObjCGCAttr())
-      DeducedQs.removeObjCGCAttr();
-    if (ParamQs.hasAddressSpace())
-      DeducedQs.removeAddressSpace();
-    if (ParamQs.hasObjCLifetime())
-      DeducedQs.removeObjCLifetime();
-
-    // Objective-C ARC:
-    //   If template deduction would produce a lifetime qualifier on a type
-    //   that is not a lifetime type, template argument deduction fails.
-    if (ParamQs.hasObjCLifetime() && !DeducedType->isObjCLifetimeType() &&
-        !DeducedType->isDependentType()) {
-      Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
-      Info.FirstArg = TemplateArgument(Param);
-      Info.SecondArg = TemplateArgument(Arg);
-      return Sema::TDK_Underqualified;
-    }
-
-    // Objective-C ARC:
-    //   If template deduction would produce an argument type with lifetime type
-    //   but no lifetime qualifier, the __strong lifetime qualifier is inferred.
-    if (S.getLangOpts().ObjCAutoRefCount &&
-        DeducedType->isObjCLifetimeType() &&
-        !DeducedQs.hasObjCLifetime())
-      DeducedQs.setObjCLifetime(Qualifiers::OCL_Strong);
-
-    DeducedType = S.Context.getQualifiedType(DeducedType.getUnqualifiedType(),
-                                             DeducedQs);
-
-    if (RecanonicalizeArg)
-      DeducedType = S.Context.getCanonicalType(DeducedType);
-
-    DeducedTemplateArgument NewDeduced(DeducedType, DeducedFromArrayBound);
-    DeducedTemplateArgument Result = checkDeducedTemplateArguments(S.Context,
-                                                                 Deduced[Index],
-                                                                   NewDeduced);
-    if (Result.isNull()) {
-      Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
-      Info.FirstArg = Deduced[Index];
-      Info.SecondArg = NewDeduced;
-      return Sema::TDK_Inconsistent;
-    }
-
-    Deduced[Index] = Result;
-    return Sema::TDK_Success;
-  }
-
-  // Set up the template argument deduction information for a failure.
-  Info.FirstArg = TemplateArgument(ParamIn);
-  Info.SecondArg = TemplateArgument(ArgIn);
-
-  // If the parameter is an already-substituted template parameter
-  // pack, do nothing: we don't know which of its arguments to look
-  // at, so we have to wait until all of the parameter packs in this
-  // expansion have arguments.
-  if (isa<SubstTemplateTypeParmPackType>(Param))
-    return Sema::TDK_Success;
-
-  // Check the cv-qualifiers on the parameter and argument types.
-  CanQualType CanParam = S.Context.getCanonicalType(Param);
-  CanQualType CanArg = S.Context.getCanonicalType(Arg);
-  if (!(TDF & TDF_IgnoreQualifiers)) {
-    if (TDF & TDF_ParamWithReferenceType) {
-      if (hasInconsistentOrSupersetQualifiersOf(Param, Arg))
-        return Sema::TDK_NonDeducedMismatch;
-    } else if (TDF & TDF_ArgWithReferenceType) {
-      // C++ [temp.deduct.conv]p4:
-      //   If the original A is a reference type, A can be more cv-qualified
-      //   than the deduced A
-      if (!Arg.getQualifiers().compatiblyIncludes(Param.getQualifiers()))
-        return Sema::TDK_NonDeducedMismatch;
-
-      // Strip out all extra qualifiers from the argument to figure out the
-      // type we're converting to, prior to the qualification conversion.
-      Qualifiers Quals;
-      Arg = S.Context.getUnqualifiedArrayType(Arg, Quals);
-      Arg = S.Context.getQualifiedType(Arg, Param.getQualifiers());
-    } else if (!IsPossiblyOpaquelyQualifiedType(Param)) {
-      if (Param.getCVRQualifiers() != Arg.getCVRQualifiers())
-        return Sema::TDK_NonDeducedMismatch;
-    }
-
-    // If the parameter type is not dependent, there is nothing to deduce.
-    if (!Param->isDependentType()) {
-      if (!(TDF & TDF_SkipNonDependent)) {
-        bool NonDeduced =
-            (TDF & TDF_AllowCompatibleFunctionType)
-                ? !S.isSameOrCompatibleFunctionType(CanParam, CanArg)
-                : Param != Arg;
-        if (NonDeduced) {
-          return Sema::TDK_NonDeducedMismatch;
-        }
-      }
-      return Sema::TDK_Success;
-    }
-  } else if (!Param->isDependentType()) {
-    CanQualType ParamUnqualType = CanParam.getUnqualifiedType(),
-                ArgUnqualType = CanArg.getUnqualifiedType();
-    bool Success =
-        (TDF & TDF_AllowCompatibleFunctionType)
-            ? S.isSameOrCompatibleFunctionType(ParamUnqualType, ArgUnqualType)
-            : ParamUnqualType == ArgUnqualType;
-    if (Success)
-      return Sema::TDK_Success;
-  }
-
-  switch (Param->getTypeClass()) {
-    // Non-canonical types cannot appear here.
-#define NON_CANONICAL_TYPE(Class, Base) \
-  case Type::Class: llvm_unreachable("deducing non-canonical type: " #Class);
-#define TYPE(Class, Base)
-#include "clang/AST/TypeNodes.def"
-
-    case Type::TemplateTypeParm:
-    case Type::SubstTemplateTypeParmPack:
-      llvm_unreachable("Type nodes handled above");
-
-    // These types cannot be dependent, so simply check whether the types are
-    // the same.
-    case Type::Builtin:
-    case Type::VariableArray:
-    case Type::Vector:
-    case Type::FunctionNoProto:
-    case Type::Record:
-    case Type::Enum:
-    case Type::ObjCObject:
-    case Type::ObjCInterface:
-    case Type::ObjCObjectPointer:
-      if (TDF & TDF_SkipNonDependent)
-        return Sema::TDK_Success;
-
-      if (TDF & TDF_IgnoreQualifiers) {
-        Param = Param.getUnqualifiedType();
-        Arg = Arg.getUnqualifiedType();
-      }
-
-      return Param == Arg? Sema::TDK_Success : Sema::TDK_NonDeducedMismatch;
-
-    //     _Complex T   [placeholder extension]
-    case Type::Complex:
-      if (const ComplexType *ComplexArg = Arg->getAs<ComplexType>())
-        return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                    cast<ComplexType>(Param)->getElementType(),
-                                    ComplexArg->getElementType(),
-                                    Info, Deduced, TDF);
-
-      return Sema::TDK_NonDeducedMismatch;
-
-    //     _Atomic T   [extension]
-    case Type::Atomic:
-      if (const AtomicType *AtomicArg = Arg->getAs<AtomicType>())
-        return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                       cast<AtomicType>(Param)->getValueType(),
-                                       AtomicArg->getValueType(),
-                                       Info, Deduced, TDF);
-
-      return Sema::TDK_NonDeducedMismatch;
-
-    //     T *
-    case Type::Pointer: {
-      QualType PointeeType;
-      if (const PointerType *PointerArg = Arg->getAs<PointerType>()) {
-        PointeeType = PointerArg->getPointeeType();
-      } else if (const ObjCObjectPointerType *PointerArg
-                   = Arg->getAs<ObjCObjectPointerType>()) {
-        PointeeType = PointerArg->getPointeeType();
-      } else {
-        return Sema::TDK_NonDeducedMismatch;
-      }
-
-      unsigned SubTDF = TDF & (TDF_IgnoreQualifiers | TDF_DerivedClass);
-      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                     cast<PointerType>(Param)->getPointeeType(),
-                                     PointeeType,
-                                     Info, Deduced, SubTDF);
-    }
-
-    //     T &
-    case Type::LValueReference: {
-      const LValueReferenceType *ReferenceArg =
-          Arg->getAs<LValueReferenceType>();
-      if (!ReferenceArg)
-        return Sema::TDK_NonDeducedMismatch;
-
-      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                           cast<LValueReferenceType>(Param)->getPointeeType(),
-                           ReferenceArg->getPointeeType(), Info, Deduced, 0);
-    }
-
-    //     T && [C++0x]
-    case Type::RValueReference: {
-      const RValueReferenceType *ReferenceArg =
-          Arg->getAs<RValueReferenceType>();
-      if (!ReferenceArg)
-        return Sema::TDK_NonDeducedMismatch;
-
-      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                             cast<RValueReferenceType>(Param)->getPointeeType(),
-                             ReferenceArg->getPointeeType(),
-                             Info, Deduced, 0);
-    }
-
-    //     T [] (implied, but not stated explicitly)
-    case Type::IncompleteArray: {
-      const IncompleteArrayType *IncompleteArrayArg =
-        S.Context.getAsIncompleteArrayType(Arg);
-      if (!IncompleteArrayArg)
-        return Sema::TDK_NonDeducedMismatch;
-
-      unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
-      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                    S.Context.getAsIncompleteArrayType(Param)->getElementType(),
-                    IncompleteArrayArg->getElementType(),
-                    Info, Deduced, SubTDF);
-    }
-
-    //     T [integer-constant]
-    case Type::ConstantArray: {
-      const ConstantArrayType *ConstantArrayArg =
-        S.Context.getAsConstantArrayType(Arg);
-      if (!ConstantArrayArg)
-        return Sema::TDK_NonDeducedMismatch;
-
-      const ConstantArrayType *ConstantArrayParm =
-        S.Context.getAsConstantArrayType(Param);
-      if (ConstantArrayArg->getSize() != ConstantArrayParm->getSize())
-        return Sema::TDK_NonDeducedMismatch;
-
-      unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
-      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                           ConstantArrayParm->getElementType(),
-                                           ConstantArrayArg->getElementType(),
-                                           Info, Deduced, SubTDF);
-    }
-
-    //     type [i]
-    case Type::DependentSizedArray: {
-      const ArrayType *ArrayArg = S.Context.getAsArrayType(Arg);
-      if (!ArrayArg)
-        return Sema::TDK_NonDeducedMismatch;
-
-      unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
-
-      // Check the element type of the arrays
-      const DependentSizedArrayType *DependentArrayParm
-        = S.Context.getAsDependentSizedArrayType(Param);
-      if (Sema::TemplateDeductionResult Result
-            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                          DependentArrayParm->getElementType(),
-                                          ArrayArg->getElementType(),
-                                          Info, Deduced, SubTDF))
-        return Result;
-
-      // Determine the array bound is something we can deduce.
-      NonTypeTemplateParmDecl *NTTP
-        = getDeducedParameterFromExpr(Info, DependentArrayParm->getSizeExpr());
-      if (!NTTP)
-        return Sema::TDK_Success;
-
-      // We can perform template argument deduction for the given non-type
-      // template parameter.
-      assert(NTTP->getDepth() == Info.getDeducedDepth() &&
-             "saw non-type template parameter with wrong depth");
-      if (const ConstantArrayType *ConstantArrayArg
-            = dyn_cast<ConstantArrayType>(ArrayArg)) {
-        llvm::APSInt Size(ConstantArrayArg->getSize());
-        return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, Size,
-                                             S.Context.getSizeType(),
-                                             /*ArrayBound=*/true,
-                                             Info, Deduced);
-      }
-      if (const DependentSizedArrayType *DependentArrayArg
-            = dyn_cast<DependentSizedArrayType>(ArrayArg))
-        if (DependentArrayArg->getSizeExpr())
-          return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
-                                               DependentArrayArg->getSizeExpr(),
-                                               Info, Deduced);
-
-      // Incomplete type does not match a dependently-sized array type
-      return Sema::TDK_NonDeducedMismatch;
-    }
-
-    //     type(*)(T)
-    //     T(*)()
-    //     T(*)(T)
-    case Type::FunctionProto: {
-      unsigned SubTDF = TDF & TDF_TopLevelParameterTypeList;
-      const FunctionProtoType *FunctionProtoArg =
-        dyn_cast<FunctionProtoType>(Arg);
-      if (!FunctionProtoArg)
-        return Sema::TDK_NonDeducedMismatch;
-
-      const FunctionProtoType *FunctionProtoParam =
-        cast<FunctionProtoType>(Param);
-
-      if (FunctionProtoParam->getTypeQuals()
-            != FunctionProtoArg->getTypeQuals() ||
-          FunctionProtoParam->getRefQualifier()
-            != FunctionProtoArg->getRefQualifier() ||
-          FunctionProtoParam->isVariadic() != FunctionProtoArg->isVariadic())
-        return Sema::TDK_NonDeducedMismatch;
-
-      // Check return types.
-      if (auto Result = DeduceTemplateArgumentsByTypeMatch(
-              S, TemplateParams, FunctionProtoParam->getReturnType(),
-              FunctionProtoArg->getReturnType(), Info, Deduced, 0))
-        return Result;
-
-      // Check parameter types.
-      if (auto Result = DeduceTemplateArguments(
-              S, TemplateParams, FunctionProtoParam->param_type_begin(),
-              FunctionProtoParam->getNumParams(),
-              FunctionProtoArg->param_type_begin(),
-              FunctionProtoArg->getNumParams(), Info, Deduced, SubTDF))
-        return Result;
-
-      if (TDF & TDF_AllowCompatibleFunctionType)
-        return Sema::TDK_Success;
-
-      // FIXME: Per core-2016/10/1019 (no corresponding core issue yet), permit
-      // deducing through the noexcept-specifier if it's part of the canonical
-      // type. libstdc++ relies on this.
-      Expr *NoexceptExpr = FunctionProtoParam->getNoexceptExpr();
-      if (NonTypeTemplateParmDecl *NTTP =
-          NoexceptExpr ? getDeducedParameterFromExpr(Info, NoexceptExpr)
-                       : nullptr) {
-        assert(NTTP->getDepth() == Info.getDeducedDepth() &&
-               "saw non-type template parameter with wrong depth");
-
-        llvm::APSInt Noexcept(1);
-        switch (FunctionProtoArg->canThrow()) {
-        case CT_Cannot:
-          Noexcept = 1;
-          LLVM_FALLTHROUGH;
-
-        case CT_Can:
-          // We give E in noexcept(E) the "deduced from array bound" treatment.
-          // FIXME: Should we?
-          return DeduceNonTypeTemplateArgument(
-              S, TemplateParams, NTTP, Noexcept, S.Context.BoolTy,
-              /*ArrayBound*/true, Info, Deduced);
-
-        case CT_Dependent:
-          if (Expr *ArgNoexceptExpr = FunctionProtoArg->getNoexceptExpr())
-            return DeduceNonTypeTemplateArgument(
-                S, TemplateParams, NTTP, ArgNoexceptExpr, Info, Deduced);
-          // Can't deduce anything from throw(T...).
-          break;
-        }
-      }
-      // FIXME: Detect non-deduced exception specification mismatches?
-      //
-      // Careful about [temp.deduct.call] and [temp.deduct.conv], which allow
-      // top-level differences in noexcept-specifications.
-
-      return Sema::TDK_Success;
-    }
-
-    case Type::InjectedClassName:
-      // Treat a template's injected-class-name as if the template
-      // specialization type had been used.
-      Param = cast<InjectedClassNameType>(Param)
-        ->getInjectedSpecializationType();
-      assert(isa<TemplateSpecializationType>(Param) &&
-             "injected class name is not a template specialization type");
-      LLVM_FALLTHROUGH;
-
-    //     template-name<T> (where template-name refers to a class template)
-    //     template-name<i>
-    //     TT<T>
-    //     TT<i>
-    //     TT<>
-    case Type::TemplateSpecialization: {
-      const TemplateSpecializationType *SpecParam =
-          cast<TemplateSpecializationType>(Param);
-
-      // When Arg cannot be a derived class, we can just try to deduce template
-      // arguments from the template-id.
-      const RecordType *RecordT = Arg->getAs<RecordType>();
-      if (!(TDF & TDF_DerivedClass) || !RecordT)
-        return DeduceTemplateArguments(S, TemplateParams, SpecParam, Arg, Info,
-                                       Deduced);
-
-      SmallVector<DeducedTemplateArgument, 8> DeducedOrig(Deduced.begin(),
-                                                          Deduced.end());
-
-      Sema::TemplateDeductionResult Result = DeduceTemplateArguments(
-          S, TemplateParams, SpecParam, Arg, Info, Deduced);
-
-      if (Result == Sema::TDK_Success)
-        return Result;
-
-      // We cannot inspect base classes as part of deduction when the type
-      // is incomplete, so either instantiate any templates necessary to
-      // complete the type, or skip over it if it cannot be completed.
-      if (!S.isCompleteType(Info.getLocation(), Arg))
-        return Result;
-
-      // C++14 [temp.deduct.call] p4b3:
-      //   If P is a class and P has the form simple-template-id, then the
-      //   transformed A can be a derived class of the deduced A. Likewise if
-      //   P is a pointer to a class of the form simple-template-id, the
-      //   transformed A can be a pointer to a derived class pointed to by the
-      //   deduced A.
-      //
-      //   These alternatives are considered only if type deduction would
-      //   otherwise fail. If they yield more than one possible deduced A, the
-      //   type deduction fails.
-
-      // Reset the incorrectly deduced argument from above.
-      Deduced = DeducedOrig;
-
-      // Use data recursion to crawl through the list of base classes.
-      // Visited contains the set of nodes we have already visited, while
-      // ToVisit is our stack of records that we still need to visit.
-      llvm::SmallPtrSet<const RecordType *, 8> Visited;
-      SmallVector<const RecordType *, 8> ToVisit;
-      ToVisit.push_back(RecordT);
-      bool Successful = false;
-      SmallVector<DeducedTemplateArgument, 8> SuccessfulDeduced;
-      while (!ToVisit.empty()) {
-        // Retrieve the next class in the inheritance hierarchy.
-        const RecordType *NextT = ToVisit.pop_back_val();
-
-        // If we have already seen this type, skip it.
-        if (!Visited.insert(NextT).second)
-          continue;
-
-        // If this is a base class, try to perform template argument
-        // deduction from it.
-        if (NextT != RecordT) {
-          TemplateDeductionInfo BaseInfo(Info.getLocation());
-          Sema::TemplateDeductionResult BaseResult =
-              DeduceTemplateArguments(S, TemplateParams, SpecParam,
-                                      QualType(NextT, 0), BaseInfo, Deduced);
-
-          // If template argument deduction for this base was successful,
-          // note that we had some success. Otherwise, ignore any deductions
-          // from this base class.
-          if (BaseResult == Sema::TDK_Success) {
-            // If we've already seen some success, then deduction fails due to
-            // an ambiguity (temp.deduct.call p5).
-            if (Successful)
-              return Sema::TDK_MiscellaneousDeductionFailure;
-
-            Successful = true;
-            std::swap(SuccessfulDeduced, Deduced);
-
-            Info.Param = BaseInfo.Param;
-            Info.FirstArg = BaseInfo.FirstArg;
-            Info.SecondArg = BaseInfo.SecondArg;
-          }
-
-          Deduced = DeducedOrig;
-        }
-
-        // Visit base classes
-        CXXRecordDecl *Next = cast<CXXRecordDecl>(NextT->getDecl());
-        for (const auto &Base : Next->bases()) {
-          assert(Base.getType()->isRecordType() &&
-                 "Base class that isn't a record?");
-          ToVisit.push_back(Base.getType()->getAs<RecordType>());
-        }
-      }
-
-      if (Successful) {
-        std::swap(SuccessfulDeduced, Deduced);
-        return Sema::TDK_Success;
-      }
-
-      return Result;
-    }
-
-    //     T type::*
-    //     T T::*
-    //     T (type::*)()
-    //     type (T::*)()
-    //     type (type::*)(T)
-    //     type (T::*)(T)
-    //     T (type::*)(T)
-    //     T (T::*)()
-    //     T (T::*)(T)
-    case Type::MemberPointer: {
-      const MemberPointerType *MemPtrParam = cast<MemberPointerType>(Param);
-      const MemberPointerType *MemPtrArg = dyn_cast<MemberPointerType>(Arg);
-      if (!MemPtrArg)
-        return Sema::TDK_NonDeducedMismatch;
-
-      QualType ParamPointeeType = MemPtrParam->getPointeeType();
-      if (ParamPointeeType->isFunctionType())
-        S.adjustMemberFunctionCC(ParamPointeeType, /*IsStatic=*/true,
-                                 /*IsCtorOrDtor=*/false, Info.getLocation());
-      QualType ArgPointeeType = MemPtrArg->getPointeeType();
-      if (ArgPointeeType->isFunctionType())
-        S.adjustMemberFunctionCC(ArgPointeeType, /*IsStatic=*/true,
-                                 /*IsCtorOrDtor=*/false, Info.getLocation());
-
-      if (Sema::TemplateDeductionResult Result
-            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                                 ParamPointeeType,
-                                                 ArgPointeeType,
-                                                 Info, Deduced,
-                                                 TDF & TDF_IgnoreQualifiers))
-        return Result;
-
-      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                           QualType(MemPtrParam->getClass(), 0),
-                                           QualType(MemPtrArg->getClass(), 0),
-                                           Info, Deduced,
-                                           TDF & TDF_IgnoreQualifiers);
-    }
-
-    //     (clang extension)
-    //
-    //     type(^)(T)
-    //     T(^)()
-    //     T(^)(T)
-    case Type::BlockPointer: {
-      const BlockPointerType *BlockPtrParam = cast<BlockPointerType>(Param);
-      const BlockPointerType *BlockPtrArg = dyn_cast<BlockPointerType>(Arg);
-
-      if (!BlockPtrArg)
-        return Sema::TDK_NonDeducedMismatch;
-
-      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                                BlockPtrParam->getPointeeType(),
-                                                BlockPtrArg->getPointeeType(),
-                                                Info, Deduced, 0);
-    }
-
-    //     (clang extension)
-    //
-    //     T __attribute__(((ext_vector_type(<integral constant>))))
-    case Type::ExtVector: {
-      const ExtVectorType *VectorParam = cast<ExtVectorType>(Param);
-      if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
-        // Make sure that the vectors have the same number of elements.
-        if (VectorParam->getNumElements() != VectorArg->getNumElements())
-          return Sema::TDK_NonDeducedMismatch;
-
-        // Perform deduction on the element types.
-        return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                                  VectorParam->getElementType(),
-                                                  VectorArg->getElementType(),
-                                                  Info, Deduced, TDF);
-      }
-
-      if (const DependentSizedExtVectorType *VectorArg
-                                = dyn_cast<DependentSizedExtVectorType>(Arg)) {
-        // We can't check the number of elements, since the argument has a
-        // dependent number of elements. This can only occur during partial
-        // ordering.
-
-        // Perform deduction on the element types.
-        return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                                  VectorParam->getElementType(),
-                                                  VectorArg->getElementType(),
-                                                  Info, Deduced, TDF);
-      }
-
-      return Sema::TDK_NonDeducedMismatch;
-    }
-
-    case Type::DependentVector: {
-      const auto *VectorParam = cast<DependentVectorType>(Param);
-
-      if (const auto *VectorArg = dyn_cast<VectorType>(Arg)) {
-        // Perform deduction on the element types.
-        if (Sema::TemplateDeductionResult Result =
-                DeduceTemplateArgumentsByTypeMatch(
-                    S, TemplateParams, VectorParam->getElementType(),
-                    VectorArg->getElementType(), Info, Deduced, TDF))
-          return Result;
-
-        // Perform deduction on the vector size, if we can.
-        NonTypeTemplateParmDecl *NTTP =
-            getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
-        if (!NTTP)
-          return Sema::TDK_Success;
-
-        llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
-        ArgSize = VectorArg->getNumElements();
-        // Note that we use the "array bound" rules here; just like in that
-        // case, we don't have any particular type for the vector size, but
-        // we can provide one if necessary.
-        return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
-                                             S.Context.UnsignedIntTy, true,
-                                             Info, Deduced);
-      }
-
-      if (const auto *VectorArg = dyn_cast<DependentVectorType>(Arg)) {
-        // Perform deduction on the element types.
-        if (Sema::TemplateDeductionResult Result =
-                DeduceTemplateArgumentsByTypeMatch(
-                    S, TemplateParams, VectorParam->getElementType(),
-                    VectorArg->getElementType(), Info, Deduced, TDF))
-          return Result;
-
-        // Perform deduction on the vector size, if we can.
-        NonTypeTemplateParmDecl *NTTP = getDeducedParameterFromExpr(
-            Info, VectorParam->getSizeExpr());
-        if (!NTTP)
-          return Sema::TDK_Success;
-
-        return DeduceNonTypeTemplateArgument(
-            S, TemplateParams, NTTP, VectorArg->getSizeExpr(), Info, Deduced);
-      }
-
-      return Sema::TDK_NonDeducedMismatch;
-    }
-
-    //     (clang extension)
-    //
-    //     T __attribute__(((ext_vector_type(N))))
-    case Type::DependentSizedExtVector: {
-      const DependentSizedExtVectorType *VectorParam
-        = cast<DependentSizedExtVectorType>(Param);
-
-      if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
-        // Perform deduction on the element types.
-        if (Sema::TemplateDeductionResult Result
-              = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                                  VectorParam->getElementType(),
-                                                   VectorArg->getElementType(),
-                                                   Info, Deduced, TDF))
-          return Result;
-
-        // Perform deduction on the vector size, if we can.
-        NonTypeTemplateParmDecl *NTTP
-          = getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
-        if (!NTTP)
-          return Sema::TDK_Success;
-
-        llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
-        ArgSize = VectorArg->getNumElements();
-        // Note that we use the "array bound" rules here; just like in that
-        // case, we don't have any particular type for the vector size, but
-        // we can provide one if necessary.
-        return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
-                                             S.Context.IntTy, true, Info,
-                                             Deduced);
-      }
-
-      if (const DependentSizedExtVectorType *VectorArg
-                                = dyn_cast<DependentSizedExtVectorType>(Arg)) {
-        // Perform deduction on the element types.
-        if (Sema::TemplateDeductionResult Result
-            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                                 VectorParam->getElementType(),
-                                                 VectorArg->getElementType(),
-                                                 Info, Deduced, TDF))
-          return Result;
-
-        // Perform deduction on the vector size, if we can.
-        NonTypeTemplateParmDecl *NTTP
-          = getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
-        if (!NTTP)
-          return Sema::TDK_Success;
-
-        return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
-                                             VectorArg->getSizeExpr(),
-                                             Info, Deduced);
-      }
-
-      return Sema::TDK_NonDeducedMismatch;
-    }
-
-    //     (clang extension)
-    //
-    //     T __attribute__(((address_space(N))))
-    case Type::DependentAddressSpace: {
-      const DependentAddressSpaceType *AddressSpaceParam =
-          cast<DependentAddressSpaceType>(Param);
-
-      if (const DependentAddressSpaceType *AddressSpaceArg =
-              dyn_cast<DependentAddressSpaceType>(Arg)) {
-        // Perform deduction on the pointer type.
-        if (Sema::TemplateDeductionResult Result =
-                DeduceTemplateArgumentsByTypeMatch(
-                    S, TemplateParams, AddressSpaceParam->getPointeeType(),
-                    AddressSpaceArg->getPointeeType(), Info, Deduced, TDF))
-          return Result;
-
-        // Perform deduction on the address space, if we can.
-        NonTypeTemplateParmDecl *NTTP = getDeducedParameterFromExpr(
-            Info, AddressSpaceParam->getAddrSpaceExpr());
-        if (!NTTP)
-          return Sema::TDK_Success;
-
-        return DeduceNonTypeTemplateArgument(
-            S, TemplateParams, NTTP, AddressSpaceArg->getAddrSpaceExpr(), Info,
-            Deduced);
-      }
-
-      if (isTargetAddressSpace(Arg.getAddressSpace())) {
-        llvm::APSInt ArgAddressSpace(S.Context.getTypeSize(S.Context.IntTy),
-                                     false);
-        ArgAddressSpace = toTargetAddressSpace(Arg.getAddressSpace());
-
-        // Perform deduction on the pointer types.
-        if (Sema::TemplateDeductionResult Result =
-                DeduceTemplateArgumentsByTypeMatch(
-                    S, TemplateParams, AddressSpaceParam->getPointeeType(),
-                    S.Context.removeAddrSpaceQualType(Arg), Info, Deduced, TDF))
-          return Result;
-
-        // Perform deduction on the address space, if we can.
-        NonTypeTemplateParmDecl *NTTP = getDeducedParameterFromExpr(
-            Info, AddressSpaceParam->getAddrSpaceExpr());
-        if (!NTTP)
-          return Sema::TDK_Success;
-
-        return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
-                                             ArgAddressSpace, S.Context.IntTy,
-                                             true, Info, Deduced);
-      }
-
-      return Sema::TDK_NonDeducedMismatch;
-    }
-
-    case Type::TypeOfExpr:
-    case Type::TypeOf:
-    case Type::DependentName:
-    case Type::UnresolvedUsing:
-    case Type::Decltype:
-    case Type::UnaryTransform:
-    case Type::Auto:
-    case Type::DeducedTemplateSpecialization:
-    case Type::DependentTemplateSpecialization:
-    case Type::PackExpansion:
-    case Type::Pipe:
-      // No template argument deduction for these types
-      return Sema::TDK_Success;
-  }
-
-  llvm_unreachable("Invalid Type Class!");
-}
-
-static Sema::TemplateDeductionResult
-DeduceTemplateArguments(Sema &S,
-                        TemplateParameterList *TemplateParams,
-                        const TemplateArgument &Param,
-                        TemplateArgument Arg,
-                        TemplateDeductionInfo &Info,
-                        SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
-  // If the template argument is a pack expansion, perform template argument
-  // deduction against the pattern of that expansion. This only occurs during
-  // partial ordering.
-  if (Arg.isPackExpansion())
-    Arg = Arg.getPackExpansionPattern();
-
-  switch (Param.getKind()) {
-  case TemplateArgument::Null:
-    llvm_unreachable("Null template argument in parameter list");
-
-  case TemplateArgument::Type:
-    if (Arg.getKind() == TemplateArgument::Type)
-      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                                Param.getAsType(),
-                                                Arg.getAsType(),
-                                                Info, Deduced, 0);
-    Info.FirstArg = Param;
-    Info.SecondArg = Arg;
-    return Sema::TDK_NonDeducedMismatch;
-
-  case TemplateArgument::Template:
-    if (Arg.getKind() == TemplateArgument::Template)
-      return DeduceTemplateArguments(S, TemplateParams,
-                                     Param.getAsTemplate(),
-                                     Arg.getAsTemplate(), Info, Deduced);
-    Info.FirstArg = Param;
-    Info.SecondArg = Arg;
-    return Sema::TDK_NonDeducedMismatch;
-
-  case TemplateArgument::TemplateExpansion:
-    llvm_unreachable("caller should handle pack expansions");
-
-  case TemplateArgument::Declaration:
-    if (Arg.getKind() == TemplateArgument::Declaration &&
-        isSameDeclaration(Param.getAsDecl(), Arg.getAsDecl()))
-      return Sema::TDK_Success;
-
-    Info.FirstArg = Param;
-    Info.SecondArg = Arg;
-    return Sema::TDK_NonDeducedMismatch;
-
-  case TemplateArgument::NullPtr:
-    if (Arg.getKind() == TemplateArgument::NullPtr &&
-        S.Context.hasSameType(Param.getNullPtrType(), Arg.getNullPtrType()))
-      return Sema::TDK_Success;
-
-    Info.FirstArg = Param;
-    Info.SecondArg = Arg;
-    return Sema::TDK_NonDeducedMismatch;
-
-  case TemplateArgument::Integral:
-    if (Arg.getKind() == TemplateArgument::Integral) {
-      if (hasSameExtendedValue(Param.getAsIntegral(), Arg.getAsIntegral()))
-        return Sema::TDK_Success;
-
-      Info.FirstArg = Param;
-      Info.SecondArg = Arg;
-      return Sema::TDK_NonDeducedMismatch;
-    }
-
-    if (Arg.getKind() == TemplateArgument::Expression) {
-      Info.FirstArg = Param;
-      Info.SecondArg = Arg;
-      return Sema::TDK_NonDeducedMismatch;
-    }
-
-    Info.FirstArg = Param;
-    Info.SecondArg = Arg;
-    return Sema::TDK_NonDeducedMismatch;
-
-  case TemplateArgument::Expression:
-    if (NonTypeTemplateParmDecl *NTTP
-          = getDeducedParameterFromExpr(Info, Param.getAsExpr())) {
-      if (Arg.getKind() == TemplateArgument::Integral)
-        return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
-                                             Arg.getAsIntegral(),
-                                             Arg.getIntegralType(),
-                                             /*ArrayBound=*/false,
-                                             Info, Deduced);
-      if (Arg.getKind() == TemplateArgument::NullPtr)
-        return DeduceNullPtrTemplateArgument(S, TemplateParams, NTTP,
-                                             Arg.getNullPtrType(),
-                                             Info, Deduced);
-      if (Arg.getKind() == TemplateArgument::Expression)
-        return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
-                                             Arg.getAsExpr(), Info, Deduced);
-      if (Arg.getKind() == TemplateArgument::Declaration)
-        return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
-                                             Arg.getAsDecl(),
-                                             Arg.getParamTypeForDecl(),
-                                             Info, Deduced);
-
-      Info.FirstArg = Param;
-      Info.SecondArg = Arg;
-      return Sema::TDK_NonDeducedMismatch;
-    }
-
-    // Can't deduce anything, but that's okay.
-    return Sema::TDK_Success;
-
-  case TemplateArgument::Pack:
-    llvm_unreachable("Argument packs should be expanded by the caller!");
-  }
-
-  llvm_unreachable("Invalid TemplateArgument Kind!");
-}
-
-/// Determine whether there is a template argument to be used for
-/// deduction.
-///
-/// This routine "expands" argument packs in-place, overriding its input
-/// parameters so that \c Args[ArgIdx] will be the available template argument.
-///
-/// \returns true if there is another template argument (which will be at
-/// \c Args[ArgIdx]), false otherwise.
-static bool hasTemplateArgumentForDeduction(ArrayRef<TemplateArgument> &Args,
-                                            unsigned &ArgIdx) {
-  if (ArgIdx == Args.size())
-    return false;
-
-  const TemplateArgument &Arg = Args[ArgIdx];
-  if (Arg.getKind() != TemplateArgument::Pack)
-    return true;
-
-  assert(ArgIdx == Args.size() - 1 && "Pack not at the end of argument list?");
-  Args = Arg.pack_elements();
-  ArgIdx = 0;
-  return ArgIdx < Args.size();
-}
-
-/// Determine whether the given set of template arguments has a pack
-/// expansion that is not the last template argument.
-static bool hasPackExpansionBeforeEnd(ArrayRef<TemplateArgument> Args) {
-  bool FoundPackExpansion = false;
-  for (const auto &A : Args) {
-    if (FoundPackExpansion)
-      return true;
-
-    if (A.getKind() == TemplateArgument::Pack)
-      return hasPackExpansionBeforeEnd(A.pack_elements());
-
-    // FIXME: If this is a fixed-arity pack expansion from an outer level of
-    // templates, it should not be treated as a pack expansion.
-    if (A.isPackExpansion())
-      FoundPackExpansion = true;
-  }
-
-  return false;
-}
-
-static Sema::TemplateDeductionResult
-DeduceTemplateArguments(Sema &S, TemplateParameterList *TemplateParams,
-                        ArrayRef<TemplateArgument> Params,
-                        ArrayRef<TemplateArgument> Args,
-                        TemplateDeductionInfo &Info,
-                        SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-                        bool NumberOfArgumentsMustMatch) {
-  // C++0x [temp.deduct.type]p9:
-  //   If the template argument list of P contains a pack expansion that is not
-  //   the last template argument, the entire template argument list is a
-  //   non-deduced context.
-  if (hasPackExpansionBeforeEnd(Params))
-    return Sema::TDK_Success;
-
-  // C++0x [temp.deduct.type]p9:
-  //   If P has a form that contains <T> or <i>, then each argument Pi of the
-  //   respective template argument list P is compared with the corresponding
-  //   argument Ai of the corresponding template argument list of A.
-  unsigned ArgIdx = 0, ParamIdx = 0;
-  for (; hasTemplateArgumentForDeduction(Params, ParamIdx); ++ParamIdx) {
-    if (!Params[ParamIdx].isPackExpansion()) {
-      // The simple case: deduce template arguments by matching Pi and Ai.
-
-      // Check whether we have enough arguments.
-      if (!hasTemplateArgumentForDeduction(Args, ArgIdx))
-        return NumberOfArgumentsMustMatch
-                   ? Sema::TDK_MiscellaneousDeductionFailure
-                   : Sema::TDK_Success;
-
-      // C++1z [temp.deduct.type]p9:
-      //   During partial ordering, if Ai was originally a pack expansion [and]
-      //   Pi is not a pack expansion, template argument deduction fails.
-      if (Args[ArgIdx].isPackExpansion())
-        return Sema::TDK_MiscellaneousDeductionFailure;
-
-      // Perform deduction for this Pi/Ai pair.
-      if (Sema::TemplateDeductionResult Result
-            = DeduceTemplateArguments(S, TemplateParams,
-                                      Params[ParamIdx], Args[ArgIdx],
-                                      Info, Deduced))
-        return Result;
-
-      // Move to the next argument.
-      ++ArgIdx;
-      continue;
-    }
-
-    // The parameter is a pack expansion.
-
-    // C++0x [temp.deduct.type]p9:
-    //   If Pi is a pack expansion, then the pattern of Pi is compared with
-    //   each remaining argument in the template argument list of A. Each
-    //   comparison deduces template arguments for subsequent positions in the
-    //   template parameter packs expanded by Pi.
-    TemplateArgument Pattern = Params[ParamIdx].getPackExpansionPattern();
-
-    // Prepare to deduce the packs within the pattern.
-    PackDeductionScope PackScope(S, TemplateParams, Deduced, Info, Pattern);
-
-    // Keep track of the deduced template arguments for each parameter pack
-    // expanded by this pack expansion (the outer index) and for each
-    // template argument (the inner SmallVectors).
-    for (; hasTemplateArgumentForDeduction(Args, ArgIdx) &&
-           PackScope.hasNextElement();
-         ++ArgIdx) {
-      // Deduce template arguments from the pattern.
-      if (Sema::TemplateDeductionResult Result
-            = DeduceTemplateArguments(S, TemplateParams, Pattern, Args[ArgIdx],
-                                      Info, Deduced))
-        return Result;
-
-      PackScope.nextPackElement();
-    }
-
-    // Build argument packs for each of the parameter packs expanded by this
-    // pack expansion.
-    if (auto Result = PackScope.finish())
-      return Result;
-  }
-
-  return Sema::TDK_Success;
-}
-
-static Sema::TemplateDeductionResult
-DeduceTemplateArguments(Sema &S,
-                        TemplateParameterList *TemplateParams,
-                        const TemplateArgumentList &ParamList,
-                        const TemplateArgumentList &ArgList,
-                        TemplateDeductionInfo &Info,
-                        SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
-  return DeduceTemplateArguments(S, TemplateParams, ParamList.asArray(),
-                                 ArgList.asArray(), Info, Deduced,
-                                 /*NumberOfArgumentsMustMatch*/false);
-}
-
-/// Determine whether two template arguments are the same.
-static bool isSameTemplateArg(ASTContext &Context,
-                              TemplateArgument X,
-                              const TemplateArgument &Y,
-                              bool PackExpansionMatchesPack = false) {
-  // If we're checking deduced arguments (X) against original arguments (Y),
-  // we will have flattened packs to non-expansions in X.
-  if (PackExpansionMatchesPack && X.isPackExpansion() && !Y.isPackExpansion())
-    X = X.getPackExpansionPattern();
-
-  if (X.getKind() != Y.getKind())
-    return false;
-
-  switch (X.getKind()) {
-    case TemplateArgument::Null:
-      llvm_unreachable("Comparing NULL template argument");
-
-    case TemplateArgument::Type:
-      return Context.getCanonicalType(X.getAsType()) ==
-             Context.getCanonicalType(Y.getAsType());
-
-    case TemplateArgument::Declaration:
-      return isSameDeclaration(X.getAsDecl(), Y.getAsDecl());
-
-    case TemplateArgument::NullPtr:
-      return Context.hasSameType(X.getNullPtrType(), Y.getNullPtrType());
-
-    case TemplateArgument::Template:
-    case TemplateArgument::TemplateExpansion:
-      return Context.getCanonicalTemplateName(
-                    X.getAsTemplateOrTemplatePattern()).getAsVoidPointer() ==
-             Context.getCanonicalTemplateName(
-                    Y.getAsTemplateOrTemplatePattern()).getAsVoidPointer();
-
-    case TemplateArgument::Integral:
-      return hasSameExtendedValue(X.getAsIntegral(), Y.getAsIntegral());
-
-    case TemplateArgument::Expression: {
-      llvm::FoldingSetNodeID XID, YID;
-      X.getAsExpr()->Profile(XID, Context, true);
-      Y.getAsExpr()->Profile(YID, Context, true);
-      return XID == YID;
-    }
-
-    case TemplateArgument::Pack:
-      if (X.pack_size() != Y.pack_size())
-        return false;
-
-      for (TemplateArgument::pack_iterator XP = X.pack_begin(),
-                                        XPEnd = X.pack_end(),
-                                           YP = Y.pack_begin();
-           XP != XPEnd; ++XP, ++YP)
-        if (!isSameTemplateArg(Context, *XP, *YP, PackExpansionMatchesPack))
-          return false;
-
-      return true;
-  }
-
-  llvm_unreachable("Invalid TemplateArgument Kind!");
-}
-
-/// Allocate a TemplateArgumentLoc where all locations have
-/// been initialized to the given location.
-///
-/// \param Arg The template argument we are producing template argument
-/// location information for.
-///
-/// \param NTTPType For a declaration template argument, the type of
-/// the non-type template parameter that corresponds to this template
-/// argument. Can be null if no type sugar is available to add to the
-/// type from the template argument.
-///
-/// \param Loc The source location to use for the resulting template
-/// argument.
-TemplateArgumentLoc
-Sema::getTrivialTemplateArgumentLoc(const TemplateArgument &Arg,
-                                    QualType NTTPType, SourceLocation Loc) {
-  switch (Arg.getKind()) {
-  case TemplateArgument::Null:
-    llvm_unreachable("Can't get a NULL template argument here");
-
-  case TemplateArgument::Type:
-    return TemplateArgumentLoc(
-        Arg, Context.getTrivialTypeSourceInfo(Arg.getAsType(), Loc));
-
-  case TemplateArgument::Declaration: {
-    if (NTTPType.isNull())
-      NTTPType = Arg.getParamTypeForDecl();
-    Expr *E = BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
-                  .getAs<Expr>();
-    return TemplateArgumentLoc(TemplateArgument(E), E);
-  }
-
-  case TemplateArgument::NullPtr: {
-    if (NTTPType.isNull())
-      NTTPType = Arg.getNullPtrType();
-    Expr *E = BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
-                  .getAs<Expr>();
-    return TemplateArgumentLoc(TemplateArgument(NTTPType, /*isNullPtr*/true),
-                               E);
-  }
-
-  case TemplateArgument::Integral: {
-    Expr *E =
-        BuildExpressionFromIntegralTemplateArgument(Arg, Loc).getAs<Expr>();
-    return TemplateArgumentLoc(TemplateArgument(E), E);
-  }
-
-    case TemplateArgument::Template:
-    case TemplateArgument::TemplateExpansion: {
-      NestedNameSpecifierLocBuilder Builder;
-      TemplateName Template = Arg.getAsTemplate();
-      if (DependentTemplateName *DTN = Template.getAsDependentTemplateName())
-        Builder.MakeTrivial(Context, DTN->getQualifier(), Loc);
-      else if (QualifiedTemplateName *QTN =
-                   Template.getAsQualifiedTemplateName())
-        Builder.MakeTrivial(Context, QTN->getQualifier(), Loc);
-
-      if (Arg.getKind() == TemplateArgument::Template)
-        return TemplateArgumentLoc(Arg, Builder.getWithLocInContext(Context),
-                                   Loc);
-
-      return TemplateArgumentLoc(Arg, Builder.getWithLocInContext(Context),
-                                 Loc, Loc);
-    }
-
-  case TemplateArgument::Expression:
-    return TemplateArgumentLoc(Arg, Arg.getAsExpr());
-
-  case TemplateArgument::Pack:
-    return TemplateArgumentLoc(Arg, TemplateArgumentLocInfo());
-  }
-
-  llvm_unreachable("Invalid TemplateArgument Kind!");
-}
-
-/// Convert the given deduced template argument and add it to the set of
-/// fully-converted template arguments.
-static bool
-ConvertDeducedTemplateArgument(Sema &S, NamedDecl *Param,
-                               DeducedTemplateArgument Arg,
-                               NamedDecl *Template,
-                               TemplateDeductionInfo &Info,
-                               bool IsDeduced,
-                               SmallVectorImpl<TemplateArgument> &Output) {
-  auto ConvertArg = [&](DeducedTemplateArgument Arg,
-                        unsigned ArgumentPackIndex) {
-    // Convert the deduced template argument into a template
-    // argument that we can check, almost as if the user had written
-    // the template argument explicitly.
-    TemplateArgumentLoc ArgLoc =
-        S.getTrivialTemplateArgumentLoc(Arg, QualType(), Info.getLocation());
-
-    // Check the template argument, converting it as necessary.
-    return S.CheckTemplateArgument(
-        Param, ArgLoc, Template, Template->getLocation(),
-        Template->getSourceRange().getEnd(), ArgumentPackIndex, Output,
-        IsDeduced
-            ? (Arg.wasDeducedFromArrayBound() ? Sema::CTAK_DeducedFromArrayBound
-                                              : Sema::CTAK_Deduced)
-            : Sema::CTAK_Specified);
-  };
-
-  if (Arg.getKind() == TemplateArgument::Pack) {
-    // This is a template argument pack, so check each of its arguments against
-    // the template parameter.
-    SmallVector<TemplateArgument, 2> PackedArgsBuilder;
-    for (const auto &P : Arg.pack_elements()) {
-      // When converting the deduced template argument, append it to the
-      // general output list. We need to do this so that the template argument
-      // checking logic has all of the prior template arguments available.
-      DeducedTemplateArgument InnerArg(P);
-      InnerArg.setDeducedFromArrayBound(Arg.wasDeducedFromArrayBound());
-      assert(InnerArg.getKind() != TemplateArgument::Pack &&
-             "deduced nested pack");
-      if (P.isNull()) {
-        // We deduced arguments for some elements of this pack, but not for
-        // all of them. This happens if we get a conditionally-non-deduced
-        // context in a pack expansion (such as an overload set in one of the
-        // arguments).
-        S.Diag(Param->getLocation(),
-               diag::err_template_arg_deduced_incomplete_pack)
-          << Arg << Param;
-        return true;
-      }
-      if (ConvertArg(InnerArg, PackedArgsBuilder.size()))
-        return true;
-
-      // Move the converted template argument into our argument pack.
-      PackedArgsBuilder.push_back(Output.pop_back_val());
-    }
-
-    // If the pack is empty, we still need to substitute into the parameter
-    // itself, in case that substitution fails.
-    if (PackedArgsBuilder.empty()) {
-      LocalInstantiationScope Scope(S);
-      TemplateArgumentList TemplateArgs(TemplateArgumentList::OnStack, Output);
-      MultiLevelTemplateArgumentList Args(TemplateArgs);
-
-      if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
-        Sema::InstantiatingTemplate Inst(S, Template->getLocation(), Template,
-                                         NTTP, Output,
-                                         Template->getSourceRange());
-        if (Inst.isInvalid() ||
-            S.SubstType(NTTP->getType(), Args, NTTP->getLocation(),
-                        NTTP->getDeclName()).isNull())
-          return true;
-      } else if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(Param)) {
-        Sema::InstantiatingTemplate Inst(S, Template->getLocation(), Template,
-                                         TTP, Output,
-                                         Template->getSourceRange());
-        if (Inst.isInvalid() || !S.SubstDecl(TTP, S.CurContext, Args))
-          return true;
-      }
-      // For type parameters, no substitution is ever required.
-    }
-
-    // Create the resulting argument pack.
-    Output.push_back(
-        TemplateArgument::CreatePackCopy(S.Context, PackedArgsBuilder));
-    return false;
-  }
-
-  return ConvertArg(Arg, 0);
-}
-
-// FIXME: This should not be a template, but
-// ClassTemplatePartialSpecializationDecl sadly does not derive from
-// TemplateDecl.
-template<typename TemplateDeclT>
-static Sema::TemplateDeductionResult ConvertDeducedTemplateArguments(
-    Sema &S, TemplateDeclT *Template, bool IsDeduced,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-    TemplateDeductionInfo &Info, SmallVectorImpl<TemplateArgument> &Builder,
-    LocalInstantiationScope *CurrentInstantiationScope = nullptr,
-    unsigned NumAlreadyConverted = 0, bool PartialOverloading = false) {
-  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
-
-  for (unsigned I = 0, N = TemplateParams->size(); I != N; ++I) {
-    NamedDecl *Param = TemplateParams->getParam(I);
-
-    // C++0x [temp.arg.explicit]p3:
-    //    A trailing template parameter pack (14.5.3) not otherwise deduced will
-    //    be deduced to an empty sequence of template arguments.
-    // FIXME: Where did the word "trailing" come from?
-    if (Deduced[I].isNull() && Param->isTemplateParameterPack()) {
-      if (auto Result = PackDeductionScope(S, TemplateParams, Deduced, Info, I)
-                            .finish(/*TreatNoDeductionsAsNonDeduced*/false))
-        return Result;
-    }
-
-    if (!Deduced[I].isNull()) {
-      if (I < NumAlreadyConverted) {
-        // We may have had explicitly-specified template arguments for a
-        // template parameter pack (that may or may not have been extended
-        // via additional deduced arguments).
-        if (Param->isParameterPack() && CurrentInstantiationScope &&
-            CurrentInstantiationScope->getPartiallySubstitutedPack() == Param) {
-          // Forget the partially-substituted pack; its substitution is now
-          // complete.
-          CurrentInstantiationScope->ResetPartiallySubstitutedPack();
-          // We still need to check the argument in case it was extended by
-          // deduction.
-        } else {
-          // We have already fully type-checked and converted this
-          // argument, because it was explicitly-specified. Just record the
-          // presence of this argument.
-          Builder.push_back(Deduced[I]);
-          continue;
-        }
-      }
-
-      // We may have deduced this argument, so it still needs to be
-      // checked and converted.
-      if (ConvertDeducedTemplateArgument(S, Param, Deduced[I], Template, Info,
-                                         IsDeduced, Builder)) {
-        Info.Param = makeTemplateParameter(Param);
-        // FIXME: These template arguments are temporary. Free them!
-        Info.reset(TemplateArgumentList::CreateCopy(S.Context, Builder));
-        return Sema::TDK_SubstitutionFailure;
-      }
-
-      continue;
-    }
-
-    // Substitute into the default template argument, if available.
-    bool HasDefaultArg = false;
-    TemplateDecl *TD = dyn_cast<TemplateDecl>(Template);
-    if (!TD) {
-      assert(isa<ClassTemplatePartialSpecializationDecl>(Template) ||
-             isa<VarTemplatePartialSpecializationDecl>(Template));
-      return Sema::TDK_Incomplete;
-    }
-
-    TemplateArgumentLoc DefArg = S.SubstDefaultTemplateArgumentIfAvailable(
-        TD, TD->getLocation(), TD->getSourceRange().getEnd(), Param, Builder,
-        HasDefaultArg);
-
-    // If there was no default argument, deduction is incomplete.
-    if (DefArg.getArgument().isNull()) {
-      Info.Param = makeTemplateParameter(
-          const_cast<NamedDecl *>(TemplateParams->getParam(I)));
-      Info.reset(TemplateArgumentList::CreateCopy(S.Context, Builder));
-      if (PartialOverloading) break;
-
-      return HasDefaultArg ? Sema::TDK_SubstitutionFailure
-                           : Sema::TDK_Incomplete;
-    }
-
-    // Check whether we can actually use the default argument.
-    if (S.CheckTemplateArgument(Param, DefArg, TD, TD->getLocation(),
-                                TD->getSourceRange().getEnd(), 0, Builder,
-                                Sema::CTAK_Specified)) {
-      Info.Param = makeTemplateParameter(
-                         const_cast<NamedDecl *>(TemplateParams->getParam(I)));
-      // FIXME: These template arguments are temporary. Free them!
-      Info.reset(TemplateArgumentList::CreateCopy(S.Context, Builder));
-      return Sema::TDK_SubstitutionFailure;
-    }
-
-    // If we get here, we successfully used the default template argument.
-  }
-
-  return Sema::TDK_Success;
-}
-
-static DeclContext *getAsDeclContextOrEnclosing(Decl *D) {
-  if (auto *DC = dyn_cast<DeclContext>(D))
-    return DC;
-  return D->getDeclContext();
-}
-
-template<typename T> struct IsPartialSpecialization {
-  static constexpr bool value = false;
-};
-template<>
-struct IsPartialSpecialization<ClassTemplatePartialSpecializationDecl> {
-  static constexpr bool value = true;
-};
-template<>
-struct IsPartialSpecialization<VarTemplatePartialSpecializationDecl> {
-  static constexpr bool value = true;
-};
-
-/// Complete template argument deduction for a partial specialization.
-template <typename T>
-static typename std::enable_if<IsPartialSpecialization<T>::value,
-                               Sema::TemplateDeductionResult>::type
-FinishTemplateArgumentDeduction(
-    Sema &S, T *Partial, bool IsPartialOrdering,
-    const TemplateArgumentList &TemplateArgs,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-    TemplateDeductionInfo &Info) {
-  // Unevaluated SFINAE context.
-  EnterExpressionEvaluationContext Unevaluated(
-      S, Sema::ExpressionEvaluationContext::Unevaluated);
-  Sema::SFINAETrap Trap(S);
-
-  Sema::ContextRAII SavedContext(S, getAsDeclContextOrEnclosing(Partial));
-
-  // C++ [temp.deduct.type]p2:
-  //   [...] or if any template argument remains neither deduced nor
-  //   explicitly specified, template argument deduction fails.
-  SmallVector<TemplateArgument, 4> Builder;
-  if (auto Result = ConvertDeducedTemplateArguments(
-          S, Partial, IsPartialOrdering, Deduced, Info, Builder))
-    return Result;
-
-  // Form the template argument list from the deduced template arguments.
-  TemplateArgumentList *DeducedArgumentList
-    = TemplateArgumentList::CreateCopy(S.Context, Builder);
-
-  Info.reset(DeducedArgumentList);
-
-  // Substitute the deduced template arguments into the template
-  // arguments of the class template partial specialization, and
-  // verify that the instantiated template arguments are both valid
-  // and are equivalent to the template arguments originally provided
-  // to the class template.
-  LocalInstantiationScope InstScope(S);
-  auto *Template = Partial->getSpecializedTemplate();
-  const ASTTemplateArgumentListInfo *PartialTemplArgInfo =
-      Partial->getTemplateArgsAsWritten();
-  const TemplateArgumentLoc *PartialTemplateArgs =
-      PartialTemplArgInfo->getTemplateArgs();
-
-  TemplateArgumentListInfo InstArgs(PartialTemplArgInfo->LAngleLoc,
-                                    PartialTemplArgInfo->RAngleLoc);
-
-  if (S.Subst(PartialTemplateArgs, PartialTemplArgInfo->NumTemplateArgs,
-              InstArgs, MultiLevelTemplateArgumentList(*DeducedArgumentList))) {
-    unsigned ArgIdx = InstArgs.size(), ParamIdx = ArgIdx;
-    if (ParamIdx >= Partial->getTemplateParameters()->size())
-      ParamIdx = Partial->getTemplateParameters()->size() - 1;
-
-    Decl *Param = const_cast<NamedDecl *>(
-        Partial->getTemplateParameters()->getParam(ParamIdx));
-    Info.Param = makeTemplateParameter(Param);
-    Info.FirstArg = PartialTemplateArgs[ArgIdx].getArgument();
-    return Sema::TDK_SubstitutionFailure;
-  }
-
-  SmallVector<TemplateArgument, 4> ConvertedInstArgs;
-  if (S.CheckTemplateArgumentList(Template, Partial->getLocation(), InstArgs,
-                                  false, ConvertedInstArgs))
-    return Sema::TDK_SubstitutionFailure;
-
-  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
-  for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
-    TemplateArgument InstArg = ConvertedInstArgs.data()[I];
-    if (!isSameTemplateArg(S.Context, TemplateArgs[I], InstArg)) {
-      Info.Param = makeTemplateParameter(TemplateParams->getParam(I));
-      Info.FirstArg = TemplateArgs[I];
-      Info.SecondArg = InstArg;
-      return Sema::TDK_NonDeducedMismatch;
-    }
-  }
-
-  if (Trap.hasErrorOccurred())
-    return Sema::TDK_SubstitutionFailure;
-
-  return Sema::TDK_Success;
-}
-
-/// Complete template argument deduction for a class or variable template,
-/// when partial ordering against a partial specialization.
-// FIXME: Factor out duplication with partial specialization version above.
-static Sema::TemplateDeductionResult FinishTemplateArgumentDeduction(
-    Sema &S, TemplateDecl *Template, bool PartialOrdering,
-    const TemplateArgumentList &TemplateArgs,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-    TemplateDeductionInfo &Info) {
-  // Unevaluated SFINAE context.
-  EnterExpressionEvaluationContext Unevaluated(
-      S, Sema::ExpressionEvaluationContext::Unevaluated);
-  Sema::SFINAETrap Trap(S);
-
-  Sema::ContextRAII SavedContext(S, getAsDeclContextOrEnclosing(Template));
-
-  // C++ [temp.deduct.type]p2:
-  //   [...] or if any template argument remains neither deduced nor
-  //   explicitly specified, template argument deduction fails.
-  SmallVector<TemplateArgument, 4> Builder;
-  if (auto Result = ConvertDeducedTemplateArguments(
-          S, Template, /*IsDeduced*/PartialOrdering, Deduced, Info, Builder))
-    return Result;
-
-  // Check that we produced the correct argument list.
-  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
-  for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
-    TemplateArgument InstArg = Builder[I];
-    if (!isSameTemplateArg(S.Context, TemplateArgs[I], InstArg,
-                           /*PackExpansionMatchesPack*/true)) {
-      Info.Param = makeTemplateParameter(TemplateParams->getParam(I));
-      Info.FirstArg = TemplateArgs[I];
-      Info.SecondArg = InstArg;
-      return Sema::TDK_NonDeducedMismatch;
-    }
-  }
-
-  if (Trap.hasErrorOccurred())
-    return Sema::TDK_SubstitutionFailure;
-
-  return Sema::TDK_Success;
-}
-
-
-/// Perform template argument deduction to determine whether
-/// the given template arguments match the given class template
-/// partial specialization per C++ [temp.class.spec.match].
-Sema::TemplateDeductionResult
-Sema::DeduceTemplateArguments(ClassTemplatePartialSpecializationDecl *Partial,
-                              const TemplateArgumentList &TemplateArgs,
-                              TemplateDeductionInfo &Info) {
-  if (Partial->isInvalidDecl())
-    return TDK_Invalid;
-
-  // C++ [temp.class.spec.match]p2:
-  //   A partial specialization matches a given actual template
-  //   argument list if the template arguments of the partial
-  //   specialization can be deduced from the actual template argument
-  //   list (14.8.2).
-
-  // Unevaluated SFINAE context.
-  EnterExpressionEvaluationContext Unevaluated(
-      *this, Sema::ExpressionEvaluationContext::Unevaluated);
-  SFINAETrap Trap(*this);
-
-  SmallVector<DeducedTemplateArgument, 4> Deduced;
-  Deduced.resize(Partial->getTemplateParameters()->size());
-  if (TemplateDeductionResult Result
-        = ::DeduceTemplateArguments(*this,
-                                    Partial->getTemplateParameters(),
-                                    Partial->getTemplateArgs(),
-                                    TemplateArgs, Info, Deduced))
-    return Result;
-
-  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
-  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
-                             Info);
-  if (Inst.isInvalid())
-    return TDK_InstantiationDepth;
-
-  if (Trap.hasErrorOccurred())
-    return Sema::TDK_SubstitutionFailure;
-
-  return ::FinishTemplateArgumentDeduction(
-      *this, Partial, /*PartialOrdering=*/false, TemplateArgs, Deduced, Info);
-}
-
-/// Perform template argument deduction to determine whether
-/// the given template arguments match the given variable template
-/// partial specialization per C++ [temp.class.spec.match].
-Sema::TemplateDeductionResult
-Sema::DeduceTemplateArguments(VarTemplatePartialSpecializationDecl *Partial,
-                              const TemplateArgumentList &TemplateArgs,
-                              TemplateDeductionInfo &Info) {
-  if (Partial->isInvalidDecl())
-    return TDK_Invalid;
-
-  // C++ [temp.class.spec.match]p2:
-  //   A partial specialization matches a given actual template
-  //   argument list if the template arguments of the partial
-  //   specialization can be deduced from the actual template argument
-  //   list (14.8.2).
-
-  // Unevaluated SFINAE context.
-  EnterExpressionEvaluationContext Unevaluated(
-      *this, Sema::ExpressionEvaluationContext::Unevaluated);
-  SFINAETrap Trap(*this);
-
-  SmallVector<DeducedTemplateArgument, 4> Deduced;
-  Deduced.resize(Partial->getTemplateParameters()->size());
-  if (TemplateDeductionResult Result = ::DeduceTemplateArguments(
-          *this, Partial->getTemplateParameters(), Partial->getTemplateArgs(),
-          TemplateArgs, Info, Deduced))
-    return Result;
-
-  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
-  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
-                             Info);
-  if (Inst.isInvalid())
-    return TDK_InstantiationDepth;
-
-  if (Trap.hasErrorOccurred())
-    return Sema::TDK_SubstitutionFailure;
-
-  return ::FinishTemplateArgumentDeduction(
-      *this, Partial, /*PartialOrdering=*/false, TemplateArgs, Deduced, Info);
-}
-
-/// Determine whether the given type T is a simple-template-id type.
-static bool isSimpleTemplateIdType(QualType T) {
-  if (const TemplateSpecializationType *Spec
-        = T->getAs<TemplateSpecializationType>())
-    return Spec->getTemplateName().getAsTemplateDecl() != nullptr;
-
-  // C++17 [temp.local]p2:
-  //   the injected-class-name [...] is equivalent to the template-name followed
-  //   by the template-arguments of the class template specialization or partial
-  //   specialization enclosed in <>
-  // ... which means it's equivalent to a simple-template-id.
-  //
-  // This only arises during class template argument deduction for a copy
-  // deduction candidate, where it permits slicing.
-  if (T->getAs<InjectedClassNameType>())
-    return true;
-
-  return false;
-}
-
-/// Substitute the explicitly-provided template arguments into the
-/// given function template according to C++ [temp.arg.explicit].
-///
-/// \param FunctionTemplate the function template into which the explicit
-/// template arguments will be substituted.
-///
-/// \param ExplicitTemplateArgs the explicitly-specified template
-/// arguments.
-///
-/// \param Deduced the deduced template arguments, which will be populated
-/// with the converted and checked explicit template arguments.
-///
-/// \param ParamTypes will be populated with the instantiated function
-/// parameters.
-///
-/// \param FunctionType if non-NULL, the result type of the function template
-/// will also be instantiated and the pointed-to value will be updated with
-/// the instantiated function type.
-///
-/// \param Info if substitution fails for any reason, this object will be
-/// populated with more information about the failure.
-///
-/// \returns TDK_Success if substitution was successful, or some failure
-/// condition.
-Sema::TemplateDeductionResult
-Sema::SubstituteExplicitTemplateArguments(
-                                      FunctionTemplateDecl *FunctionTemplate,
-                               TemplateArgumentListInfo &ExplicitTemplateArgs,
-                       SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-                                 SmallVectorImpl<QualType> &ParamTypes,
-                                          QualType *FunctionType,
-                                          TemplateDeductionInfo &Info) {
-  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
-  TemplateParameterList *TemplateParams
-    = FunctionTemplate->getTemplateParameters();
-
-  if (ExplicitTemplateArgs.size() == 0) {
-    // No arguments to substitute; just copy over the parameter types and
-    // fill in the function type.
-    for (auto P : Function->parameters())
-      ParamTypes.push_back(P->getType());
-
-    if (FunctionType)
-      *FunctionType = Function->getType();
-    return TDK_Success;
-  }
-
-  // Unevaluated SFINAE context.
-  EnterExpressionEvaluationContext Unevaluated(
-      *this, Sema::ExpressionEvaluationContext::Unevaluated);
-  SFINAETrap Trap(*this);
-
-  // C++ [temp.arg.explicit]p3:
-  //   Template arguments that are present shall be specified in the
-  //   declaration order of their corresponding template-parameters. The
-  //   template argument list shall not specify more template-arguments than
-  //   there are corresponding template-parameters.
-  SmallVector<TemplateArgument, 4> Builder;
-
-  // Enter a new template instantiation context where we check the
-  // explicitly-specified template arguments against this function template,
-  // and then substitute them into the function parameter types.
-  SmallVector<TemplateArgument, 4> DeducedArgs;
-  InstantiatingTemplate Inst(
-      *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
-      CodeSynthesisContext::ExplicitTemplateArgumentSubstitution, Info);
-  if (Inst.isInvalid())
-    return TDK_InstantiationDepth;
-
-  if (CheckTemplateArgumentList(FunctionTemplate, SourceLocation(),
-                                ExplicitTemplateArgs, true, Builder, false) ||
-      Trap.hasErrorOccurred()) {
-    unsigned Index = Builder.size();
-    if (Index >= TemplateParams->size())
-      return TDK_SubstitutionFailure;
-    Info.Param = makeTemplateParameter(TemplateParams->getParam(Index));
-    return TDK_InvalidExplicitArguments;
-  }
-
-  // Form the template argument list from the explicitly-specified
-  // template arguments.
-  TemplateArgumentList *ExplicitArgumentList
-    = TemplateArgumentList::CreateCopy(Context, Builder);
-  Info.setExplicitArgs(ExplicitArgumentList);
-
-  // Template argument deduction and the final substitution should be
-  // done in the context of the templated declaration.  Explicit
-  // argument substitution, on the other hand, needs to happen in the
-  // calling context.
-  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
-
-  // If we deduced template arguments for a template parameter pack,
-  // note that the template argument pack is partially substituted and record
-  // the explicit template arguments. They'll be used as part of deduction
-  // for this template parameter pack.
-  unsigned PartiallySubstitutedPackIndex = -1u;
-  if (!Builder.empty()) {
-    const TemplateArgument &Arg = Builder.back();
-    if (Arg.getKind() == TemplateArgument::Pack) {
-      auto *Param = TemplateParams->getParam(Builder.size() - 1);
-      // If this is a fully-saturated fixed-size pack, it should be
-      // fully-substituted, not partially-substituted.
-      Optional<unsigned> Expansions = getExpandedPackSize(Param);
-      if (!Expansions || Arg.pack_size() < *Expansions) {
-        PartiallySubstitutedPackIndex = Builder.size() - 1;
-        CurrentInstantiationScope->SetPartiallySubstitutedPack(
-            Param, Arg.pack_begin(), Arg.pack_size());
-      }
-    }
-  }
-
-  const FunctionProtoType *Proto
-    = Function->getType()->getAs<FunctionProtoType>();
-  assert(Proto && "Function template does not have a prototype?");
-
-  // Isolate our substituted parameters from our caller.
-  LocalInstantiationScope InstScope(*this, /*MergeWithOuterScope*/true);
-
-  ExtParameterInfoBuilder ExtParamInfos;
-
-  // Instantiate the types of each of the function parameters given the
-  // explicitly-specified template arguments. If the function has a trailing
-  // return type, substitute it after the arguments to ensure we substitute
-  // in lexical order.
-  if (Proto->hasTrailingReturn()) {
-    if (SubstParmTypes(Function->getLocation(), Function->parameters(),
-                       Proto->getExtParameterInfosOrNull(),
-                       MultiLevelTemplateArgumentList(*ExplicitArgumentList),
-                       ParamTypes, /*params*/ nullptr, ExtParamInfos))
-      return TDK_SubstitutionFailure;
-  }
-
-  // Instantiate the return type.
-  QualType ResultType;
-  {
-    // C++11 [expr.prim.general]p3:
-    //   If a declaration declares a member function or member function
-    //   template of a class X, the expression this is a prvalue of type
-    //   "pointer to cv-qualifier-seq X" between the optional cv-qualifer-seq
-    //   and the end of the function-definition, member-declarator, or
-    //   declarator.
-    Qualifiers ThisTypeQuals;
-    CXXRecordDecl *ThisContext = nullptr;
-    if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Function)) {
-      ThisContext = Method->getParent();
-      ThisTypeQuals = Method->getTypeQualifiers();
-    }
-
-    CXXThisScopeRAII ThisScope(*this, ThisContext, ThisTypeQuals,
-                               getLangOpts().CPlusPlus11);
-
-    ResultType =
-        SubstType(Proto->getReturnType(),
-                  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
-                  Function->getTypeSpecStartLoc(), Function->getDeclName());
-    if (ResultType.isNull() || Trap.hasErrorOccurred())
-      return TDK_SubstitutionFailure;
-  }
-
-  // Instantiate the types of each of the function parameters given the
-  // explicitly-specified template arguments if we didn't do so earlier.
-  if (!Proto->hasTrailingReturn() &&
-      SubstParmTypes(Function->getLocation(), Function->parameters(),
-                     Proto->getExtParameterInfosOrNull(),
-                     MultiLevelTemplateArgumentList(*ExplicitArgumentList),
-                     ParamTypes, /*params*/ nullptr, ExtParamInfos))
-    return TDK_SubstitutionFailure;
-
-  if (FunctionType) {
-    auto EPI = Proto->getExtProtoInfo();
-    EPI.ExtParameterInfos = ExtParamInfos.getPointerOrNull(ParamTypes.size());
-
-    // In C++1z onwards, exception specifications are part of the function type,
-    // so substitution into the type must also substitute into the exception
-    // specification.
-    SmallVector<QualType, 4> ExceptionStorage;
-    if (getLangOpts().CPlusPlus17 &&
-        SubstExceptionSpec(
-            Function->getLocation(), EPI.ExceptionSpec, ExceptionStorage,
-            MultiLevelTemplateArgumentList(*ExplicitArgumentList)))
-      return TDK_SubstitutionFailure;
-
-    *FunctionType = BuildFunctionType(ResultType, ParamTypes,
-                                      Function->getLocation(),
-                                      Function->getDeclName(),
-                                      EPI);
-    if (FunctionType->isNull() || Trap.hasErrorOccurred())
-      return TDK_SubstitutionFailure;
-  }
-
-  // C++ [temp.arg.explicit]p2:
-  //   Trailing template arguments that can be deduced (14.8.2) may be
-  //   omitted from the list of explicit template-arguments. If all of the
-  //   template arguments can be deduced, they may all be omitted; in this
-  //   case, the empty template argument list <> itself may also be omitted.
-  //
-  // Take all of the explicitly-specified arguments and put them into
-  // the set of deduced template arguments. The partially-substituted
-  // parameter pack, however, will be set to NULL since the deduction
-  // mechanism handles the partially-substituted argument pack directly.
-  Deduced.reserve(TemplateParams->size());
-  for (unsigned I = 0, N = ExplicitArgumentList->size(); I != N; ++I) {
-    const TemplateArgument &Arg = ExplicitArgumentList->get(I);
-    if (I == PartiallySubstitutedPackIndex)
-      Deduced.push_back(DeducedTemplateArgument());
-    else
-      Deduced.push_back(Arg);
-  }
-
-  return TDK_Success;
-}
-
-/// Check whether the deduced argument type for a call to a function
-/// template matches the actual argument type per C++ [temp.deduct.call]p4.
-static Sema::TemplateDeductionResult
-CheckOriginalCallArgDeduction(Sema &S, TemplateDeductionInfo &Info,
-                              Sema::OriginalCallArg OriginalArg,
-                              QualType DeducedA) {
-  ASTContext &Context = S.Context;
-
-  auto Failed = [&]() -> Sema::TemplateDeductionResult {
-    Info.FirstArg = TemplateArgument(DeducedA);
-    Info.SecondArg = TemplateArgument(OriginalArg.OriginalArgType);
-    Info.CallArgIndex = OriginalArg.ArgIdx;
-    return OriginalArg.DecomposedParam ? Sema::TDK_DeducedMismatchNested
-                                       : Sema::TDK_DeducedMismatch;
-  };
-
-  QualType A = OriginalArg.OriginalArgType;
-  QualType OriginalParamType = OriginalArg.OriginalParamType;
-
-  // Check for type equality (top-level cv-qualifiers are ignored).
-  if (Context.hasSameUnqualifiedType(A, DeducedA))
-    return Sema::TDK_Success;
-
-  // Strip off references on the argument types; they aren't needed for
-  // the following checks.
-  if (const ReferenceType *DeducedARef = DeducedA->getAs<ReferenceType>())
-    DeducedA = DeducedARef->getPointeeType();
-  if (const ReferenceType *ARef = A->getAs<ReferenceType>())
-    A = ARef->getPointeeType();
-
-  // C++ [temp.deduct.call]p4:
-  //   [...] However, there are three cases that allow a difference:
-  //     - If the original P is a reference type, the deduced A (i.e., the
-  //       type referred to by the reference) can be more cv-qualified than
-  //       the transformed A.
-  if (const ReferenceType *OriginalParamRef
-      = OriginalParamType->getAs<ReferenceType>()) {
-    // We don't want to keep the reference around any more.
-    OriginalParamType = OriginalParamRef->getPointeeType();
-
-    // FIXME: Resolve core issue (no number yet): if the original P is a
-    // reference type and the transformed A is function type "noexcept F",
-    // the deduced A can be F.
-    QualType Tmp;
-    if (A->isFunctionType() && S.IsFunctionConversion(A, DeducedA, Tmp))
-      return Sema::TDK_Success;
-
-    Qualifiers AQuals = A.getQualifiers();
-    Qualifiers DeducedAQuals = DeducedA.getQualifiers();
-
-    // Under Objective-C++ ARC, the deduced type may have implicitly
-    // been given strong or (when dealing with a const reference)
-    // unsafe_unretained lifetime. If so, update the original
-    // qualifiers to include this lifetime.
-    if (S.getLangOpts().ObjCAutoRefCount &&
-        ((DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_Strong &&
-          AQuals.getObjCLifetime() == Qualifiers::OCL_None) ||
-         (DeducedAQuals.hasConst() &&
-          DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_ExplicitNone))) {
-      AQuals.setObjCLifetime(DeducedAQuals.getObjCLifetime());
-    }
-
-    if (AQuals == DeducedAQuals) {
-      // Qualifiers match; there's nothing to do.
-    } else if (!DeducedAQuals.compatiblyIncludes(AQuals)) {
-      return Failed();
-    } else {
-      // Qualifiers are compatible, so have the argument type adopt the
-      // deduced argument type's qualifiers as if we had performed the
-      // qualification conversion.
-      A = Context.getQualifiedType(A.getUnqualifiedType(), DeducedAQuals);
-    }
-  }
-
-  //    - The transformed A can be another pointer or pointer to member
-  //      type that can be converted to the deduced A via a function pointer
-  //      conversion and/or a qualification conversion.
-  //
-  // Also allow conversions which merely strip __attribute__((noreturn)) from
-  // function types (recursively).
-  bool ObjCLifetimeConversion = false;
-  QualType ResultTy;
-  if ((A->isAnyPointerType() || A->isMemberPointerType()) &&
-      (S.IsQualificationConversion(A, DeducedA, false,
-                                   ObjCLifetimeConversion) ||
-       S.IsFunctionConversion(A, DeducedA, ResultTy)))
-    return Sema::TDK_Success;
-
-  //    - If P is a class and P has the form simple-template-id, then the
-  //      transformed A can be a derived class of the deduced A. [...]
-  //     [...] Likewise, if P is a pointer to a class of the form
-  //      simple-template-id, the transformed A can be a pointer to a
-  //      derived class pointed to by the deduced A.
-  if (const PointerType *OriginalParamPtr
-      = OriginalParamType->getAs<PointerType>()) {
-    if (const PointerType *DeducedAPtr = DeducedA->getAs<PointerType>()) {
-      if (const PointerType *APtr = A->getAs<PointerType>()) {
-        if (A->getPointeeType()->isRecordType()) {
-          OriginalParamType = OriginalParamPtr->getPointeeType();
-          DeducedA = DeducedAPtr->getPointeeType();
-          A = APtr->getPointeeType();
-        }
-      }
-    }
-  }
-
-  if (Context.hasSameUnqualifiedType(A, DeducedA))
-    return Sema::TDK_Success;
-
-  if (A->isRecordType() && isSimpleTemplateIdType(OriginalParamType) &&
-      S.IsDerivedFrom(Info.getLocation(), A, DeducedA))
-    return Sema::TDK_Success;
-
-  return Failed();
-}
-
-/// Find the pack index for a particular parameter index in an instantiation of
-/// a function template with specific arguments.
-///
-/// \return The pack index for whichever pack produced this parameter, or -1
-///         if this was not produced by a parameter. Intended to be used as the
-///         ArgumentPackSubstitutionIndex for further substitutions.
-// FIXME: We should track this in OriginalCallArgs so we don't need to
-// reconstruct it here.
-static unsigned getPackIndexForParam(Sema &S,
-                                     FunctionTemplateDecl *FunctionTemplate,
-                                     const MultiLevelTemplateArgumentList &Args,
-                                     unsigned ParamIdx) {
-  unsigned Idx = 0;
-  for (auto *PD : FunctionTemplate->getTemplatedDecl()->parameters()) {
-    if (PD->isParameterPack()) {
-      unsigned NumExpansions =
-          S.getNumArgumentsInExpansion(PD->getType(), Args).getValueOr(1);
-      if (Idx + NumExpansions > ParamIdx)
-        return ParamIdx - Idx;
-      Idx += NumExpansions;
-    } else {
-      if (Idx == ParamIdx)
-        return -1; // Not a pack expansion
-      ++Idx;
-    }
-  }
-
-  llvm_unreachable("parameter index would not be produced from template");
-}
-
-/// Finish template argument deduction for a function template,
-/// checking the deduced template arguments for completeness and forming
-/// the function template specialization.
-///
-/// \param OriginalCallArgs If non-NULL, the original call arguments against
-/// which the deduced argument types should be compared.
-Sema::TemplateDeductionResult Sema::FinishTemplateArgumentDeduction(
-    FunctionTemplateDecl *FunctionTemplate,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-    unsigned NumExplicitlySpecified, FunctionDecl *&Specialization,
-    TemplateDeductionInfo &Info,
-    SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs,
-    bool PartialOverloading, llvm::function_ref<bool()> CheckNonDependent) {
-  // Unevaluated SFINAE context.
-  EnterExpressionEvaluationContext Unevaluated(
-      *this, Sema::ExpressionEvaluationContext::Unevaluated);
-  SFINAETrap Trap(*this);
-
-  // Enter a new template instantiation context while we instantiate the
-  // actual function declaration.
-  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
-  InstantiatingTemplate Inst(
-      *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
-      CodeSynthesisContext::DeducedTemplateArgumentSubstitution, Info);
-  if (Inst.isInvalid())
-    return TDK_InstantiationDepth;
-
-  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
-
-  // C++ [temp.deduct.type]p2:
-  //   [...] or if any template argument remains neither deduced nor
-  //   explicitly specified, template argument deduction fails.
-  SmallVector<TemplateArgument, 4> Builder;
-  if (auto Result = ConvertDeducedTemplateArguments(
-          *this, FunctionTemplate, /*IsDeduced*/true, Deduced, Info, Builder,
-          CurrentInstantiationScope, NumExplicitlySpecified,
-          PartialOverloading))
-    return Result;
-
-  // C++ [temp.deduct.call]p10: [DR1391]
-  //   If deduction succeeds for all parameters that contain
-  //   template-parameters that participate in template argument deduction,
-  //   and all template arguments are explicitly specified, deduced, or
-  //   obtained from default template arguments, remaining parameters are then
-  //   compared with the corresponding arguments. For each remaining parameter
-  //   P with a type that was non-dependent before substitution of any
-  //   explicitly-specified template arguments, if the corresponding argument
-  //   A cannot be implicitly converted to P, deduction fails.
-  if (CheckNonDependent())
-    return TDK_NonDependentConversionFailure;
-
-  // Form the template argument list from the deduced template arguments.
-  TemplateArgumentList *DeducedArgumentList
-    = TemplateArgumentList::CreateCopy(Context, Builder);
-  Info.reset(DeducedArgumentList);
-
-  // Substitute the deduced template arguments into the function template
-  // declaration to produce the function template specialization.
-  DeclContext *Owner = FunctionTemplate->getDeclContext();
-  if (FunctionTemplate->getFriendObjectKind())
-    Owner = FunctionTemplate->getLexicalDeclContext();
-  MultiLevelTemplateArgumentList SubstArgs(*DeducedArgumentList);
-  Specialization = cast_or_null<FunctionDecl>(
-      SubstDecl(FunctionTemplate->getTemplatedDecl(), Owner, SubstArgs));
-  if (!Specialization || Specialization->isInvalidDecl())
-    return TDK_SubstitutionFailure;
-
-  assert(Specialization->getPrimaryTemplate()->getCanonicalDecl() ==
-         FunctionTemplate->getCanonicalDecl());
-
-  // If the template argument list is owned by the function template
-  // specialization, release it.
-  if (Specialization->getTemplateSpecializationArgs() == DeducedArgumentList &&
-      !Trap.hasErrorOccurred())
-    Info.take();
-
-  // There may have been an error that did not prevent us from constructing a
-  // declaration. Mark the declaration invalid and return with a substitution
-  // failure.
-  if (Trap.hasErrorOccurred()) {
-    Specialization->setInvalidDecl(true);
-    return TDK_SubstitutionFailure;
-  }
-
-  if (OriginalCallArgs) {
-    // C++ [temp.deduct.call]p4:
-    //   In general, the deduction process attempts to find template argument
-    //   values that will make the deduced A identical to A (after the type A
-    //   is transformed as described above). [...]
-    llvm::SmallDenseMap<std::pair<unsigned, QualType>, QualType> DeducedATypes;
-    for (unsigned I = 0, N = OriginalCallArgs->size(); I != N; ++I) {
-      OriginalCallArg OriginalArg = (*OriginalCallArgs)[I];
-
-      auto ParamIdx = OriginalArg.ArgIdx;
-      if (ParamIdx >= Specialization->getNumParams())
-        // FIXME: This presumably means a pack ended up smaller than we
-        // expected while deducing. Should this not result in deduction
-        // failure? Can it even happen?
-        continue;
-
-      QualType DeducedA;
-      if (!OriginalArg.DecomposedParam) {
-        // P is one of the function parameters, just look up its substituted
-        // type.
-        DeducedA = Specialization->getParamDecl(ParamIdx)->getType();
-      } else {
-        // P is a decomposed element of a parameter corresponding to a
-        // braced-init-list argument. Substitute back into P to find the
-        // deduced A.
-        QualType &CacheEntry =
-            DeducedATypes[{ParamIdx, OriginalArg.OriginalParamType}];
-        if (CacheEntry.isNull()) {
-          ArgumentPackSubstitutionIndexRAII PackIndex(
-              *this, getPackIndexForParam(*this, FunctionTemplate, SubstArgs,
-                                          ParamIdx));
-          CacheEntry =
-              SubstType(OriginalArg.OriginalParamType, SubstArgs,
-                        Specialization->getTypeSpecStartLoc(),
-                        Specialization->getDeclName());
-        }
-        DeducedA = CacheEntry;
-      }
-
-      if (auto TDK =
-              CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA))
-        return TDK;
-    }
-  }
-
-  // If we suppressed any diagnostics while performing template argument
-  // deduction, and if we haven't already instantiated this declaration,
-  // keep track of these diagnostics. They'll be emitted if this specialization
-  // is actually used.
-  if (Info.diag_begin() != Info.diag_end()) {
-    SuppressedDiagnosticsMap::iterator
-      Pos = SuppressedDiagnostics.find(Specialization->getCanonicalDecl());
-    if (Pos == SuppressedDiagnostics.end())
-        SuppressedDiagnostics[Specialization->getCanonicalDecl()]
-          .append(Info.diag_begin(), Info.diag_end());
-  }
-
-  return TDK_Success;
-}
-
-/// Gets the type of a function for template-argument-deducton
-/// purposes when it's considered as part of an overload set.
-static QualType GetTypeOfFunction(Sema &S, const OverloadExpr::FindResult &R,
-                                  FunctionDecl *Fn) {
-  // We may need to deduce the return type of the function now.
-  if (S.getLangOpts().CPlusPlus14 && Fn->getReturnType()->isUndeducedType() &&
-      S.DeduceReturnType(Fn, R.Expression->getExprLoc(), /*Diagnose*/ false))
-    return {};
-
-  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Fn))
-    if (Method->isInstance()) {
-      // An instance method that's referenced in a form that doesn't
-      // look like a member pointer is just invalid.
-      if (!R.HasFormOfMemberPointer)
-        return {};
-
-      return S.Context.getMemberPointerType(Fn->getType(),
-               S.Context.getTypeDeclType(Method->getParent()).getTypePtr());
-    }
-
-  if (!R.IsAddressOfOperand) return Fn->getType();
-  return S.Context.getPointerType(Fn->getType());
-}
-
-/// Apply the deduction rules for overload sets.
-///
-/// \return the null type if this argument should be treated as an
-/// undeduced context
-static QualType
-ResolveOverloadForDeduction(Sema &S, TemplateParameterList *TemplateParams,
-                            Expr *Arg, QualType ParamType,
-                            bool ParamWasReference) {
-
-  OverloadExpr::FindResult R = OverloadExpr::find(Arg);
-
-  OverloadExpr *Ovl = R.Expression;
-
-  // C++0x [temp.deduct.call]p4
-  unsigned TDF = 0;
-  if (ParamWasReference)
-    TDF |= TDF_ParamWithReferenceType;
-  if (R.IsAddressOfOperand)
-    TDF |= TDF_IgnoreQualifiers;
-
-  // C++0x [temp.deduct.call]p6:
-  //   When P is a function type, pointer to function type, or pointer
-  //   to member function type:
-
-  if (!ParamType->isFunctionType() &&
-      !ParamType->isFunctionPointerType() &&
-      !ParamType->isMemberFunctionPointerType()) {
-    if (Ovl->hasExplicitTemplateArgs()) {
-      // But we can still look for an explicit specialization.
-      if (FunctionDecl *ExplicitSpec
-            = S.ResolveSingleFunctionTemplateSpecialization(Ovl))
-        return GetTypeOfFunction(S, R, ExplicitSpec);
-    }
-
-    DeclAccessPair DAP;
-    if (FunctionDecl *Viable =
-            S.resolveAddressOfOnlyViableOverloadCandidate(Arg, DAP))
-      return GetTypeOfFunction(S, R, Viable);
-
-    return {};
-  }
-
-  // Gather the explicit template arguments, if any.
-  TemplateArgumentListInfo ExplicitTemplateArgs;
-  if (Ovl->hasExplicitTemplateArgs())
-    Ovl->copyTemplateArgumentsInto(ExplicitTemplateArgs);
-  QualType Match;
-  for (UnresolvedSetIterator I = Ovl->decls_begin(),
-         E = Ovl->decls_end(); I != E; ++I) {
-    NamedDecl *D = (*I)->getUnderlyingDecl();
-
-    if (FunctionTemplateDecl *FunTmpl = dyn_cast<FunctionTemplateDecl>(D)) {
-      //   - If the argument is an overload set containing one or more
-      //     function templates, the parameter is treated as a
-      //     non-deduced context.
-      if (!Ovl->hasExplicitTemplateArgs())
-        return {};
-
-      // Otherwise, see if we can resolve a function type
-      FunctionDecl *Specialization = nullptr;
-      TemplateDeductionInfo Info(Ovl->getNameLoc());
-      if (S.DeduceTemplateArguments(FunTmpl, &ExplicitTemplateArgs,
-                                    Specialization, Info))
-        continue;
-
-      D = Specialization;
-    }
-
-    FunctionDecl *Fn = cast<FunctionDecl>(D);
-    QualType ArgType = GetTypeOfFunction(S, R, Fn);
-    if (ArgType.isNull()) continue;
-
-    // Function-to-pointer conversion.
-    if (!ParamWasReference && ParamType->isPointerType() &&
-        ArgType->isFunctionType())
-      ArgType = S.Context.getPointerType(ArgType);
-
-    //   - If the argument is an overload set (not containing function
-    //     templates), trial argument deduction is attempted using each
-    //     of the members of the set. If deduction succeeds for only one
-    //     of the overload set members, that member is used as the
-    //     argument value for the deduction. If deduction succeeds for
-    //     more than one member of the overload set the parameter is
-    //     treated as a non-deduced context.
-
-    // We do all of this in a fresh context per C++0x [temp.deduct.type]p2:
-    //   Type deduction is done independently for each P/A pair, and
-    //   the deduced template argument values are then combined.
-    // So we do not reject deductions which were made elsewhere.
-    SmallVector<DeducedTemplateArgument, 8>
-      Deduced(TemplateParams->size());
-    TemplateDeductionInfo Info(Ovl->getNameLoc());
-    Sema::TemplateDeductionResult Result
-      = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
-                                           ArgType, Info, Deduced, TDF);
-    if (Result) continue;
-    if (!Match.isNull())
-      return {};
-    Match = ArgType;
-  }
-
-  return Match;
-}
-
-/// Perform the adjustments to the parameter and argument types
-/// described in C++ [temp.deduct.call].
-///
-/// \returns true if the caller should not attempt to perform any template
-/// argument deduction based on this P/A pair because the argument is an
-/// overloaded function set that could not be resolved.
-static bool AdjustFunctionParmAndArgTypesForDeduction(
-    Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
-    QualType &ParamType, QualType &ArgType, Expr *Arg, unsigned &TDF) {
-  // C++0x [temp.deduct.call]p3:
-  //   If P is a cv-qualified type, the top level cv-qualifiers of P's type
-  //   are ignored for type deduction.
-  if (ParamType.hasQualifiers())
-    ParamType = ParamType.getUnqualifiedType();
-
-  //   [...] If P is a reference type, the type referred to by P is
-  //   used for type deduction.
-  const ReferenceType *ParamRefType = ParamType->getAs<ReferenceType>();
-  if (ParamRefType)
-    ParamType = ParamRefType->getPointeeType();
-
-  // Overload sets usually make this parameter an undeduced context,
-  // but there are sometimes special circumstances.  Typically
-  // involving a template-id-expr.
-  if (ArgType == S.Context.OverloadTy) {
-    ArgType = ResolveOverloadForDeduction(S, TemplateParams,
-                                          Arg, ParamType,
-                                          ParamRefType != nullptr);
-    if (ArgType.isNull())
-      return true;
-  }
-
-  if (ParamRefType) {
-    // If the argument has incomplete array type, try to complete its type.
-    if (ArgType->isIncompleteArrayType()) {
-      S.completeExprArrayBound(Arg);
-      ArgType = Arg->getType();
-    }
-
-    // C++1z [temp.deduct.call]p3:
-    //   If P is a forwarding reference and the argument is an lvalue, the type
-    //   "lvalue reference to A" is used in place of A for type deduction.
-    if (isForwardingReference(QualType(ParamRefType, 0), FirstInnerIndex) &&
-        Arg->isLValue())
-      ArgType = S.Context.getLValueReferenceType(ArgType);
-  } else {
-    // C++ [temp.deduct.call]p2:
-    //   If P is not a reference type:
-    //   - If A is an array type, the pointer type produced by the
-    //     array-to-pointer standard conversion (4.2) is used in place of
-    //     A for type deduction; otherwise,
-    if (ArgType->isArrayType())
-      ArgType = S.Context.getArrayDecayedType(ArgType);
-    //   - If A is a function type, the pointer type produced by the
-    //     function-to-pointer standard conversion (4.3) is used in place
-    //     of A for type deduction; otherwise,
-    else if (ArgType->isFunctionType())
-      ArgType = S.Context.getPointerType(ArgType);
-    else {
-      // - If A is a cv-qualified type, the top level cv-qualifiers of A's
-      //   type are ignored for type deduction.
-      ArgType = ArgType.getUnqualifiedType();
-    }
-  }
-
-  // C++0x [temp.deduct.call]p4:
-  //   In general, the deduction process attempts to find template argument
-  //   values that will make the deduced A identical to A (after the type A
-  //   is transformed as described above). [...]
-  TDF = TDF_SkipNonDependent;
-
-  //     - If the original P is a reference type, the deduced A (i.e., the
-  //       type referred to by the reference) can be more cv-qualified than
-  //       the transformed A.
-  if (ParamRefType)
-    TDF |= TDF_ParamWithReferenceType;
-  //     - The transformed A can be another pointer or pointer to member
-  //       type that can be converted to the deduced A via a qualification
-  //       conversion (4.4).
-  if (ArgType->isPointerType() || ArgType->isMemberPointerType() ||
-      ArgType->isObjCObjectPointerType())
-    TDF |= TDF_IgnoreQualifiers;
-  //     - If P is a class and P has the form simple-template-id, then the
-  //       transformed A can be a derived class of the deduced A. Likewise,
-  //       if P is a pointer to a class of the form simple-template-id, the
-  //       transformed A can be a pointer to a derived class pointed to by
-  //       the deduced A.
-  if (isSimpleTemplateIdType(ParamType) ||
-      (isa<PointerType>(ParamType) &&
-       isSimpleTemplateIdType(
-                              ParamType->getAs<PointerType>()->getPointeeType())))
-    TDF |= TDF_DerivedClass;
-
-  return false;
-}
-
-static bool
-hasDeducibleTemplateParameters(Sema &S, FunctionTemplateDecl *FunctionTemplate,
-                               QualType T);
-
-static Sema::TemplateDeductionResult DeduceTemplateArgumentsFromCallArgument(
-    Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
-    QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-    SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
-    bool DecomposedParam, unsigned ArgIdx, unsigned TDF);
-
-/// Attempt template argument deduction from an initializer list
-///        deemed to be an argument in a function call.
-static Sema::TemplateDeductionResult DeduceFromInitializerList(
-    Sema &S, TemplateParameterList *TemplateParams, QualType AdjustedParamType,
-    InitListExpr *ILE, TemplateDeductionInfo &Info,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-    SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs, unsigned ArgIdx,
-    unsigned TDF) {
-  // C++ [temp.deduct.call]p1: (CWG 1591)
-  //   If removing references and cv-qualifiers from P gives
-  //   std::initializer_list<P0> or P0[N] for some P0 and N and the argument is
-  //   a non-empty initializer list, then deduction is performed instead for
-  //   each element of the initializer list, taking P0 as a function template
-  //   parameter type and the initializer element as its argument
-  //
-  // We've already removed references and cv-qualifiers here.
-  if (!ILE->getNumInits())
-    return Sema::TDK_Success;
-
-  QualType ElTy;
-  auto *ArrTy = S.Context.getAsArrayType(AdjustedParamType);
-  if (ArrTy)
-    ElTy = ArrTy->getElementType();
-  else if (!S.isStdInitializerList(AdjustedParamType, &ElTy)) {
-    //   Otherwise, an initializer list argument causes the parameter to be
-    //   considered a non-deduced context
-    return Sema::TDK_Success;
-  }
-
-  // Deduction only needs to be done for dependent types.
-  if (ElTy->isDependentType()) {
-    for (Expr *E : ILE->inits()) {
-      if (auto Result = DeduceTemplateArgumentsFromCallArgument(
-              S, TemplateParams, 0, ElTy, E, Info, Deduced, OriginalCallArgs, true,
-              ArgIdx, TDF))
-        return Result;
-    }
-  }
-
-  //   in the P0[N] case, if N is a non-type template parameter, N is deduced
-  //   from the length of the initializer list.
-  if (auto *DependentArrTy = dyn_cast_or_null<DependentSizedArrayType>(ArrTy)) {
-    // Determine the array bound is something we can deduce.
-    if (NonTypeTemplateParmDecl *NTTP =
-            getDeducedParameterFromExpr(Info, DependentArrTy->getSizeExpr())) {
-      // We can perform template argument deduction for the given non-type
-      // template parameter.
-      // C++ [temp.deduct.type]p13:
-      //   The type of N in the type T[N] is std::size_t.
-      QualType T = S.Context.getSizeType();
-      llvm::APInt Size(S.Context.getIntWidth(T), ILE->getNumInits());
-      if (auto Result = DeduceNonTypeTemplateArgument(
-              S, TemplateParams, NTTP, llvm::APSInt(Size), T,
-              /*ArrayBound=*/true, Info, Deduced))
-        return Result;
-    }
-  }
-
-  return Sema::TDK_Success;
-}
-
-/// Perform template argument deduction per [temp.deduct.call] for a
-///        single parameter / argument pair.
-static Sema::TemplateDeductionResult DeduceTemplateArgumentsFromCallArgument(
-    Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
-    QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
-    SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-    SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
-    bool DecomposedParam, unsigned ArgIdx, unsigned TDF) {
-  QualType ArgType = Arg->getType();
-  QualType OrigParamType = ParamType;
-
-  //   If P is a reference type [...]
-  //   If P is a cv-qualified type [...]
-  if (AdjustFunctionParmAndArgTypesForDeduction(
-          S, TemplateParams, FirstInnerIndex, ParamType, ArgType, Arg, TDF))
-    return Sema::TDK_Success;
-
-  //   If [...] the argument is a non-empty initializer list [...]
-  if (InitListExpr *ILE = dyn_cast<InitListExpr>(Arg))
-    return DeduceFromInitializerList(S, TemplateParams, ParamType, ILE, Info,
-                                     Deduced, OriginalCallArgs, ArgIdx, TDF);
-
-  //   [...] the deduction process attempts to find template argument values
-  //   that will make the deduced A identical to A
-  //
-  // Keep track of the argument type and corresponding parameter index,
-  // so we can check for compatibility between the deduced A and A.
-  OriginalCallArgs.push_back(
-      Sema::OriginalCallArg(OrigParamType, DecomposedParam, ArgIdx, ArgType));
-  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
-                                            ArgType, Info, Deduced, TDF);
-}
-
-/// Perform template argument deduction from a function call
-/// (C++ [temp.deduct.call]).
-///
-/// \param FunctionTemplate the function template for which we are performing
-/// template argument deduction.
-///
-/// \param ExplicitTemplateArgs the explicit template arguments provided
-/// for this call.
-///
-/// \param Args the function call arguments
-///
-/// \param Specialization if template argument deduction was successful,
-/// this will be set to the function template specialization produced by
-/// template argument deduction.
-///
-/// \param Info the argument will be updated to provide additional information
-/// about template argument deduction.
-///
-/// \param CheckNonDependent A callback to invoke to check conversions for
-/// non-dependent parameters, between deduction and substitution, per DR1391.
-/// If this returns true, substitution will be skipped and we return
-/// TDK_NonDependentConversionFailure. The callback is passed the parameter
-/// types (after substituting explicit template arguments).
-///
-/// \returns the result of template argument deduction.
-Sema::TemplateDeductionResult Sema::DeduceTemplateArguments(
-    FunctionTemplateDecl *FunctionTemplate,
-    TemplateArgumentListInfo *ExplicitTemplateArgs, ArrayRef<Expr *> Args,
-    FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
-    bool PartialOverloading,
-    llvm::function_ref<bool(ArrayRef<QualType>)> CheckNonDependent) {
-  if (FunctionTemplate->isInvalidDecl())
-    return TDK_Invalid;
-
-  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
-  unsigned NumParams = Function->getNumParams();
-
-  unsigned FirstInnerIndex = getFirstInnerIndex(FunctionTemplate);
-
-  // C++ [temp.deduct.call]p1:
-  //   Template argument deduction is done by comparing each function template
-  //   parameter type (call it P) with the type of the corresponding argument
-  //   of the call (call it A) as described below.
-  if (Args.size() < Function->getMinRequiredArguments() && !PartialOverloading)
-    return TDK_TooFewArguments;
-  else if (TooManyArguments(NumParams, Args.size(), PartialOverloading)) {
-    const FunctionProtoType *Proto
-      = Function->getType()->getAs<FunctionProtoType>();
-    if (Proto->isTemplateVariadic())
-      /* Do nothing */;
-    else if (!Proto->isVariadic())
-      return TDK_TooManyArguments;
-  }
-
-  // The types of the parameters from which we will perform template argument
-  // deduction.
-  LocalInstantiationScope InstScope(*this);
-  TemplateParameterList *TemplateParams
-    = FunctionTemplate->getTemplateParameters();
-  SmallVector<DeducedTemplateArgument, 4> Deduced;
-  SmallVector<QualType, 8> ParamTypes;
-  unsigned NumExplicitlySpecified = 0;
-  if (ExplicitTemplateArgs) {
-    TemplateDeductionResult Result =
-      SubstituteExplicitTemplateArguments(FunctionTemplate,
-                                          *ExplicitTemplateArgs,
-                                          Deduced,
-                                          ParamTypes,
-                                          nullptr,
-                                          Info);
-    if (Result)
-      return Result;
-
-    NumExplicitlySpecified = Deduced.size();
-  } else {
-    // Just fill in the parameter types from the function declaration.
-    for (unsigned I = 0; I != NumParams; ++I)
-      ParamTypes.push_back(Function->getParamDecl(I)->getType());
-  }
-
-  SmallVector<OriginalCallArg, 8> OriginalCallArgs;
-
-  // Deduce an argument of type ParamType from an expression with index ArgIdx.
-  auto DeduceCallArgument = [&](QualType ParamType, unsigned ArgIdx) {
-    // C++ [demp.deduct.call]p1: (DR1391)
-    //   Template argument deduction is done by comparing each function template
-    //   parameter that contains template-parameters that participate in
-    //   template argument deduction ...
-    if (!hasDeducibleTemplateParameters(*this, FunctionTemplate, ParamType))
-      return Sema::TDK_Success;
-
-    //   ... with the type of the corresponding argument
-    return DeduceTemplateArgumentsFromCallArgument(
-        *this, TemplateParams, FirstInnerIndex, ParamType, Args[ArgIdx], Info, Deduced,
-        OriginalCallArgs, /*Decomposed*/false, ArgIdx, /*TDF*/ 0);
-  };
-
-  // Deduce template arguments from the function parameters.
-  Deduced.resize(TemplateParams->size());
-  SmallVector<QualType, 8> ParamTypesForArgChecking;
-  for (unsigned ParamIdx = 0, NumParamTypes = ParamTypes.size(), ArgIdx = 0;
-       ParamIdx != NumParamTypes; ++ParamIdx) {
-    QualType ParamType = ParamTypes[ParamIdx];
-
-    const PackExpansionType *ParamExpansion =
-        dyn_cast<PackExpansionType>(ParamType);
-    if (!ParamExpansion) {
-      // Simple case: matching a function parameter to a function argument.
-      if (ArgIdx >= Args.size())
-        break;
-
-      ParamTypesForArgChecking.push_back(ParamType);
-      if (auto Result = DeduceCallArgument(ParamType, ArgIdx++))
-        return Result;
-
-      continue;
-    }
-
-    QualType ParamPattern = ParamExpansion->getPattern();
-    PackDeductionScope PackScope(*this, TemplateParams, Deduced, Info,
-                                 ParamPattern);
-
-    // C++0x [temp.deduct.call]p1:
-    //   For a function parameter pack that occurs at the end of the
-    //   parameter-declaration-list, the type A of each remaining argument of
-    //   the call is compared with the type P of the declarator-id of the
-    //   function parameter pack. Each comparison deduces template arguments
-    //   for subsequent positions in the template parameter packs expanded by
-    //   the function parameter pack. When a function parameter pack appears
-    //   in a non-deduced context [not at the end of the list], the type of
-    //   that parameter pack is never deduced.
-    //
-    // FIXME: The above rule allows the size of the parameter pack to change
-    // after we skip it (in the non-deduced case). That makes no sense, so
-    // we instead notionally deduce the pack against N arguments, where N is
-    // the length of the explicitly-specified pack if it's expanded by the
-    // parameter pack and 0 otherwise, and we treat each deduction as a
-    // non-deduced context.
-    if (ParamIdx + 1 == NumParamTypes || PackScope.hasFixedArity()) {
-      for (; ArgIdx < Args.size() && PackScope.hasNextElement();
-           PackScope.nextPackElement(), ++ArgIdx) {
-        ParamTypesForArgChecking.push_back(ParamPattern);
-        if (auto Result = DeduceCallArgument(ParamPattern, ArgIdx))
-          return Result;
-      }
-    } else {
-      // If the parameter type contains an explicitly-specified pack that we
-      // could not expand, skip the number of parameters notionally created
-      // by the expansion.
-      Optional<unsigned> NumExpansions = ParamExpansion->getNumExpansions();
-      if (NumExpansions && !PackScope.isPartiallyExpanded()) {
-        for (unsigned I = 0; I != *NumExpansions && ArgIdx < Args.size();
-             ++I, ++ArgIdx) {
-          ParamTypesForArgChecking.push_back(ParamPattern);
-          // FIXME: Should we add OriginalCallArgs for these? What if the
-          // corresponding argument is a list?
-          PackScope.nextPackElement();
-        }
-      }
-    }
-
-    // Build argument packs for each of the parameter packs expanded by this
-    // pack expansion.
-    if (auto Result = PackScope.finish())
-      return Result;
-  }
-
-  // Capture the context in which the function call is made. This is the context
-  // that is needed when the accessibility of template arguments is checked.
-  DeclContext *CallingCtx = CurContext;
-
-  return FinishTemplateArgumentDeduction(
-      FunctionTemplate, Deduced, NumExplicitlySpecified, Specialization, Info,
-      &OriginalCallArgs, PartialOverloading, [&, CallingCtx]() {
-        ContextRAII SavedContext(*this, CallingCtx);
-        return CheckNonDependent(ParamTypesForArgChecking);
-      });
-}
-
-QualType Sema::adjustCCAndNoReturn(QualType ArgFunctionType,
-                                   QualType FunctionType,
-                                   bool AdjustExceptionSpec) {
-  if (ArgFunctionType.isNull())
-    return ArgFunctionType;
-
-  const FunctionProtoType *FunctionTypeP =
-      FunctionType->castAs<FunctionProtoType>();
-  const FunctionProtoType *ArgFunctionTypeP =
-      ArgFunctionType->getAs<FunctionProtoType>();
-
-  FunctionProtoType::ExtProtoInfo EPI = ArgFunctionTypeP->getExtProtoInfo();
-  bool Rebuild = false;
-
-  CallingConv CC = FunctionTypeP->getCallConv();
-  if (EPI.ExtInfo.getCC() != CC) {
-    EPI.ExtInfo = EPI.ExtInfo.withCallingConv(CC);
-    Rebuild = true;
-  }
-
-  bool NoReturn = FunctionTypeP->getNoReturnAttr();
-  if (EPI.ExtInfo.getNoReturn() != NoReturn) {
-    EPI.ExtInfo = EPI.ExtInfo.withNoReturn(NoReturn);
-    Rebuild = true;
-  }
-
-  if (AdjustExceptionSpec && (FunctionTypeP->hasExceptionSpec() ||
-                              ArgFunctionTypeP->hasExceptionSpec())) {
-    EPI.ExceptionSpec = FunctionTypeP->getExtProtoInfo().ExceptionSpec;
-    Rebuild = true;
-  }
-
-  if (!Rebuild)
-    return ArgFunctionType;
-
-  return Context.getFunctionType(ArgFunctionTypeP->getReturnType(),
-                                 ArgFunctionTypeP->getParamTypes(), EPI);
-}
-
-/// Deduce template arguments when taking the address of a function
-/// template (C++ [temp.deduct.funcaddr]) or matching a specialization to
-/// a template.
-///
-/// \param FunctionTemplate the function template for which we are performing
-/// template argument deduction.
-///
-/// \param ExplicitTemplateArgs the explicitly-specified template
-/// arguments.
-///
-/// \param ArgFunctionType the function type that will be used as the
-/// "argument" type (A) when performing template argument deduction from the
-/// function template's function type. This type may be NULL, if there is no
-/// argument type to compare against, in C++0x [temp.arg.explicit]p3.
-///
-/// \param Specialization if template argument deduction was successful,
-/// this will be set to the function template specialization produced by
-/// template argument deduction.
-///
-/// \param Info the argument will be updated to provide additional information
-/// about template argument deduction.
-///
-/// \param IsAddressOfFunction If \c true, we are deducing as part of taking
-/// the address of a function template per [temp.deduct.funcaddr] and
-/// [over.over]. If \c false, we are looking up a function template
-/// specialization based on its signature, per [temp.deduct.decl].
-///
-/// \returns the result of template argument deduction.
-Sema::TemplateDeductionResult Sema::DeduceTemplateArguments(
-    FunctionTemplateDecl *FunctionTemplate,
-    TemplateArgumentListInfo *ExplicitTemplateArgs, QualType ArgFunctionType,
-    FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
-    bool IsAddressOfFunction) {
-  if (FunctionTemplate->isInvalidDecl())
-    return TDK_Invalid;
-
-  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
-  TemplateParameterList *TemplateParams
-    = FunctionTemplate->getTemplateParameters();
-  QualType FunctionType = Function->getType();
-
-  // Substitute any explicit template arguments.
-  LocalInstantiationScope InstScope(*this);
-  SmallVector<DeducedTemplateArgument, 4> Deduced;
-  unsigned NumExplicitlySpecified = 0;
-  SmallVector<QualType, 4> ParamTypes;
-  if (ExplicitTemplateArgs) {
-    if (TemplateDeductionResult Result
-          = SubstituteExplicitTemplateArguments(FunctionTemplate,
-                                                *ExplicitTemplateArgs,
-                                                Deduced, ParamTypes,
-                                                &FunctionType, Info))
-      return Result;
-
-    NumExplicitlySpecified = Deduced.size();
-  }
-
-  // When taking the address of a function, we require convertibility of
-  // the resulting function type. Otherwise, we allow arbitrary mismatches
-  // of calling convention and noreturn.
-  if (!IsAddressOfFunction)
-    ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, FunctionType,
-                                          /*AdjustExceptionSpec*/false);
-
-  // Unevaluated SFINAE context.
-  EnterExpressionEvaluationContext Unevaluated(
-      *this, Sema::ExpressionEvaluationContext::Unevaluated);
-  SFINAETrap Trap(*this);
-
-  Deduced.resize(TemplateParams->size());
-
-  // If the function has a deduced return type, substitute it for a dependent
-  // type so that we treat it as a non-deduced context in what follows. If we
-  // are looking up by signature, the signature type should also have a deduced
-  // return type, which we instead expect to exactly match.
-  bool HasDeducedReturnType = false;
-  if (getLangOpts().CPlusPlus14 && IsAddressOfFunction &&
-      Function->getReturnType()->getContainedAutoType()) {
-    FunctionType = SubstAutoType(FunctionType, Context.DependentTy);
-    HasDeducedReturnType = true;
-  }
-
-  if (!ArgFunctionType.isNull()) {
-    unsigned TDF =
-        TDF_TopLevelParameterTypeList | TDF_AllowCompatibleFunctionType;
-    // Deduce template arguments from the function type.
-    if (TemplateDeductionResult Result
-          = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
-                                               FunctionType, ArgFunctionType,
-                                               Info, Deduced, TDF))
-      return Result;
-  }
-
-  if (TemplateDeductionResult Result
-        = FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
-                                          NumExplicitlySpecified,
-                                          Specialization, Info))
-    return Result;
-
-  // If the function has a deduced return type, deduce it now, so we can check
-  // that the deduced function type matches the requested type.
-  if (HasDeducedReturnType &&
-      Specialization->getReturnType()->isUndeducedType() &&
-      DeduceReturnType(Specialization, Info.getLocation(), false))
-    return TDK_MiscellaneousDeductionFailure;
-
-  // If the function has a dependent exception specification, resolve it now,
-  // so we can check that the exception specification matches.
-  auto *SpecializationFPT =
-      Specialization->getType()->castAs<FunctionProtoType>();
-  if (getLangOpts().CPlusPlus17 &&
-      isUnresolvedExceptionSpec(SpecializationFPT->getExceptionSpecType()) &&
-      !ResolveExceptionSpec(Info.getLocation(), SpecializationFPT))
-    return TDK_MiscellaneousDeductionFailure;
-
-  // Adjust the exception specification of the argument to match the
-  // substituted and resolved type we just formed. (Calling convention and
-  // noreturn can't be dependent, so we don't actually need this for them
-  // right now.)
-  QualType SpecializationType = Specialization->getType();
-  if (!IsAddressOfFunction)
-    ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, SpecializationType,
-                                          /*AdjustExceptionSpec*/true);
-
-  // If the requested function type does not match the actual type of the
-  // specialization with respect to arguments of compatible pointer to function
-  // types, template argument deduction fails.
-  if (!ArgFunctionType.isNull()) {
-    if (IsAddressOfFunction &&
-        !isSameOrCompatibleFunctionType(
-            Context.getCanonicalType(SpecializationType),
-            Context.getCanonicalType(ArgFunctionType)))
-      return TDK_MiscellaneousDeductionFailure;
-
-    if (!IsAddressOfFunction &&
-        !Context.hasSameType(SpecializationType, ArgFunctionType))
-      return TDK_MiscellaneousDeductionFailure;
-  }
-
-  return TDK_Success;
-}
-
-/// Deduce template arguments for a templated conversion
-/// function (C++ [temp.deduct.conv]) and, if successful, produce a
-/// conversion function template specialization.
-Sema::TemplateDeductionResult
-Sema::DeduceTemplateArguments(FunctionTemplateDecl *ConversionTemplate,
-                              QualType ToType,
-                              CXXConversionDecl *&Specialization,
-                              TemplateDeductionInfo &Info) {
-  if (ConversionTemplate->isInvalidDecl())
-    return TDK_Invalid;
-
-  CXXConversionDecl *ConversionGeneric
-    = cast<CXXConversionDecl>(ConversionTemplate->getTemplatedDecl());
-
-  QualType FromType = ConversionGeneric->getConversionType();
-
-  // Canonicalize the types for deduction.
-  QualType P = Context.getCanonicalType(FromType);
-  QualType A = Context.getCanonicalType(ToType);
-
-  // C++0x [temp.deduct.conv]p2:
-  //   If P is a reference type, the type referred to by P is used for
-  //   type deduction.
-  if (const ReferenceType *PRef = P->getAs<ReferenceType>())
-    P = PRef->getPointeeType();
-
-  // C++0x [temp.deduct.conv]p4:
-  //   [...] If A is a reference type, the type referred to by A is used
-  //   for type deduction.
-  if (const ReferenceType *ARef = A->getAs<ReferenceType>()) {
-    A = ARef->getPointeeType();
-    // We work around a defect in the standard here: cv-qualifiers are also
-    // removed from P and A in this case, unless P was a reference type. This
-    // seems to mostly match what other compilers are doing.
-    if (!FromType->getAs<ReferenceType>()) {
-      A = A.getUnqualifiedType();
-      P = P.getUnqualifiedType();
-    }
-
-  // C++ [temp.deduct.conv]p3:
-  //
-  //   If A is not a reference type:
-  } else {
-    assert(!A->isReferenceType() && "Reference types were handled above");
-
-    //   - If P is an array type, the pointer type produced by the
-    //     array-to-pointer standard conversion (4.2) is used in place
-    //     of P for type deduction; otherwise,
-    if (P->isArrayType())
-      P = Context.getArrayDecayedType(P);
-    //   - If P is a function type, the pointer type produced by the
-    //     function-to-pointer standard conversion (4.3) is used in
-    //     place of P for type deduction; otherwise,
-    else if (P->isFunctionType())
-      P = Context.getPointerType(P);
-    //   - If P is a cv-qualified type, the top level cv-qualifiers of
-    //     P's type are ignored for type deduction.
-    else
-      P = P.getUnqualifiedType();
-
-    // C++0x [temp.deduct.conv]p4:
-    //   If A is a cv-qualified type, the top level cv-qualifiers of A's
-    //   type are ignored for type deduction. If A is a reference type, the type
-    //   referred to by A is used for type deduction.
-    A = A.getUnqualifiedType();
-  }
-
-  // Unevaluated SFINAE context.
-  EnterExpressionEvaluationContext Unevaluated(
-      *this, Sema::ExpressionEvaluationContext::Unevaluated);
-  SFINAETrap Trap(*this);
-
-  // C++ [temp.deduct.conv]p1:
-  //   Template argument deduction is done by comparing the return
-  //   type of the template conversion function (call it P) with the
-  //   type that is required as the result of the conversion (call it
-  //   A) as described in 14.8.2.4.
-  TemplateParameterList *TemplateParams
-    = ConversionTemplate->getTemplateParameters();
-  SmallVector<DeducedTemplateArgument, 4> Deduced;
-  Deduced.resize(TemplateParams->size());
-
-  // C++0x [temp.deduct.conv]p4:
-  //   In general, the deduction process attempts to find template
-  //   argument values that will make the deduced A identical to
-  //   A. However, there are two cases that allow a difference:
-  unsigned TDF = 0;
-  //     - If the original A is a reference type, A can be more
-  //       cv-qualified than the deduced A (i.e., the type referred to
-  //       by the reference)
-  if (ToType->isReferenceType())
-    TDF |= TDF_ArgWithReferenceType;
-  //     - The deduced A can be another pointer or pointer to member
-  //       type that can be converted to A via a qualification
-  //       conversion.
-  //
-  // (C++0x [temp.deduct.conv]p6 clarifies that this only happens when
-  // both P and A are pointers or member pointers. In this case, we
-  // just ignore cv-qualifiers completely).
-  if ((P->isPointerType() && A->isPointerType()) ||
-      (P->isMemberPointerType() && A->isMemberPointerType()))
-    TDF |= TDF_IgnoreQualifiers;
-  if (TemplateDeductionResult Result
-        = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
-                                             P, A, Info, Deduced, TDF))
-    return Result;
-
-  // Create an Instantiation Scope for finalizing the operator.
-  LocalInstantiationScope InstScope(*this);
-  // Finish template argument deduction.
-  FunctionDecl *ConversionSpecialized = nullptr;
-  TemplateDeductionResult Result
-      = FinishTemplateArgumentDeduction(ConversionTemplate, Deduced, 0,
-                                        ConversionSpecialized, Info);
-  Specialization = cast_or_null<CXXConversionDecl>(ConversionSpecialized);
-  return Result;
-}
-
-/// Deduce template arguments for a function template when there is
-/// nothing to deduce against (C++0x [temp.arg.explicit]p3).
-///
-/// \param FunctionTemplate the function template for which we are performing
-/// template argument deduction.
-///
-/// \param ExplicitTemplateArgs the explicitly-specified template
-/// arguments.
-///
-/// \param Specialization if template argument deduction was successful,
-/// this will be set to the function template specialization produced by
-/// template argument deduction.
-///
-/// \param Info the argument will be updated to provide additional information
-/// about template argument deduction.
-///
-/// \param IsAddressOfFunction If \c true, we are deducing as part of taking
-/// the address of a function template in a context where we do not have a
-/// target type, per [over.over]. If \c false, we are looking up a function
-/// template specialization based on its signature, which only happens when
-/// deducing a function parameter type from an argument that is a template-id
-/// naming a function template specialization.
-///
-/// \returns the result of template argument deduction.
-Sema::TemplateDeductionResult Sema::DeduceTemplateArguments(
-    FunctionTemplateDecl *FunctionTemplate,
-    TemplateArgumentListInfo *ExplicitTemplateArgs,
-    FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
-    bool IsAddressOfFunction) {
-  return DeduceTemplateArguments(FunctionTemplate, ExplicitTemplateArgs,
-                                 QualType(), Specialization, Info,
-                                 IsAddressOfFunction);
-}
-
-namespace {
-
-  /// Substitute the 'auto' specifier or deduced template specialization type
-  /// specifier within a type for a given replacement type.
-  class SubstituteDeducedTypeTransform :
-      public TreeTransform<SubstituteDeducedTypeTransform> {
-    QualType Replacement;
-    bool UseTypeSugar;
-
-  public:
-    SubstituteDeducedTypeTransform(Sema &SemaRef, QualType Replacement,
-                            bool UseTypeSugar = true)
-        : TreeTransform<SubstituteDeducedTypeTransform>(SemaRef),
-          Replacement(Replacement), UseTypeSugar(UseTypeSugar) {}
-
-    QualType TransformDesugared(TypeLocBuilder &TLB, DeducedTypeLoc TL) {
-      assert(isa<TemplateTypeParmType>(Replacement) &&
-             "unexpected unsugared replacement kind");
-      QualType Result = Replacement;
-      TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
-      NewTL.setNameLoc(TL.getNameLoc());
-      return Result;
-    }
-
-    QualType TransformAutoType(TypeLocBuilder &TLB, AutoTypeLoc TL) {
-      // If we're building the type pattern to deduce against, don't wrap the
-      // substituted type in an AutoType. Certain template deduction rules
-      // apply only when a template type parameter appears directly (and not if
-      // the parameter is found through desugaring). For instance:
-      //   auto &&lref = lvalue;
-      // must transform into "rvalue reference to T" not "rvalue reference to
-      // auto type deduced as T" in order for [temp.deduct.call]p3 to apply.
-      //
-      // FIXME: Is this still necessary?
-      if (!UseTypeSugar)
-        return TransformDesugared(TLB, TL);
-
-      QualType Result = SemaRef.Context.getAutoType(
-          Replacement, TL.getTypePtr()->getKeyword(), Replacement.isNull());
-      auto NewTL = TLB.push<AutoTypeLoc>(Result);
-      NewTL.setNameLoc(TL.getNameLoc());
-      return Result;
-    }
-
-    QualType TransformDeducedTemplateSpecializationType(
-        TypeLocBuilder &TLB, DeducedTemplateSpecializationTypeLoc TL) {
-      if (!UseTypeSugar)
-        return TransformDesugared(TLB, TL);
-
-      QualType Result = SemaRef.Context.getDeducedTemplateSpecializationType(
-          TL.getTypePtr()->getTemplateName(),
-          Replacement, Replacement.isNull());
-      auto NewTL = TLB.push<DeducedTemplateSpecializationTypeLoc>(Result);
-      NewTL.setNameLoc(TL.getNameLoc());
-      return Result;
-    }
-
-    ExprResult TransformLambdaExpr(LambdaExpr *E) {
-      // Lambdas never need to be transformed.
-      return E;
-    }
-
-    QualType Apply(TypeLoc TL) {
-      // Create some scratch storage for the transformed type locations.
-      // FIXME: We're just going to throw this information away. Don't build it.
-      TypeLocBuilder TLB;
-      TLB.reserve(TL.getFullDataSize());
-      return TransformType(TLB, TL);
-    }
-  };
-
-} // namespace
-
-Sema::DeduceAutoResult
-Sema::DeduceAutoType(TypeSourceInfo *Type, Expr *&Init, QualType &Result,
-                     Optional<unsigned> DependentDeductionDepth) {
-  return DeduceAutoType(Type->getTypeLoc(), Init, Result,
-                        DependentDeductionDepth);
-}
-
-/// Attempt to produce an informative diagostic explaining why auto deduction
-/// failed.
-/// \return \c true if diagnosed, \c false if not.
-static bool diagnoseAutoDeductionFailure(Sema &S,
-                                         Sema::TemplateDeductionResult TDK,
-                                         TemplateDeductionInfo &Info,
-                                         ArrayRef<SourceRange> Ranges) {
-  switch (TDK) {
-  case Sema::TDK_Inconsistent: {
-    // Inconsistent deduction means we were deducing from an initializer list.
-    auto D = S.Diag(Info.getLocation(), diag::err_auto_inconsistent_deduction);
-    D << Info.FirstArg << Info.SecondArg;
-    for (auto R : Ranges)
-      D << R;
-    return true;
-  }
-
-  // FIXME: Are there other cases for which a custom diagnostic is more useful
-  // than the basic "types don't match" diagnostic?
-
-  default:
-    return false;
-  }
-}
-
-/// Deduce the type for an auto type-specifier (C++11 [dcl.spec.auto]p6)
-///
-/// Note that this is done even if the initializer is dependent. (This is
-/// necessary to support partial ordering of templates using 'auto'.)
-/// A dependent type will be produced when deducing from a dependent type.
-///
-/// \param Type the type pattern using the auto type-specifier.
-/// \param Init the initializer for the variable whose type is to be deduced.
-/// \param Result if type deduction was successful, this will be set to the
-///        deduced type.
-/// \param DependentDeductionDepth Set if we should permit deduction in
-///        dependent cases. This is necessary for template partial ordering with
-///        'auto' template parameters. The value specified is the template
-///        parameter depth at which we should perform 'auto' deduction.
-Sema::DeduceAutoResult
-Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result,
-                     Optional<unsigned> DependentDeductionDepth) {
-  if (Init->getType()->isNonOverloadPlaceholderType()) {
-    ExprResult NonPlaceholder = CheckPlaceholderExpr(Init);
-    if (NonPlaceholder.isInvalid())
-      return DAR_FailedAlreadyDiagnosed;
-    Init = NonPlaceholder.get();
-  }
-
-  if (!DependentDeductionDepth &&
-      (Type.getType()->isDependentType() || Init->isTypeDependent())) {
-    Result = SubstituteDeducedTypeTransform(*this, QualType()).Apply(Type);
-    assert(!Result.isNull() && "substituting DependentTy can't fail");
-    return DAR_Succeeded;
-  }
-
-  // Find the depth of template parameter to synthesize.
-  unsigned Depth = DependentDeductionDepth.getValueOr(0);
-
-  // If this is a 'decltype(auto)' specifier, do the decltype dance.
-  // Since 'decltype(auto)' can only occur at the top of the type, we
-  // don't need to go digging for it.
-  if (const AutoType *AT = Type.getType()->getAs<AutoType>()) {
-    if (AT->isDecltypeAuto()) {
-      if (isa<InitListExpr>(Init)) {
-        Diag(Init->getBeginLoc(), diag::err_decltype_auto_initializer_list);
-        return DAR_FailedAlreadyDiagnosed;
-      }
-
-      ExprResult ER = CheckPlaceholderExpr(Init);
-      if (ER.isInvalid())
-        return DAR_FailedAlreadyDiagnosed;
-      Init = ER.get();
-      QualType Deduced = BuildDecltypeType(Init, Init->getBeginLoc(), false);
-      if (Deduced.isNull())
-        return DAR_FailedAlreadyDiagnosed;
-      // FIXME: Support a non-canonical deduced type for 'auto'.
-      Deduced = Context.getCanonicalType(Deduced);
-      Result = SubstituteDeducedTypeTransform(*this, Deduced).Apply(Type);
-      if (Result.isNull())
-        return DAR_FailedAlreadyDiagnosed;
-      return DAR_Succeeded;
-    } else if (!getLangOpts().CPlusPlus) {
-      if (isa<InitListExpr>(Init)) {
-        Diag(Init->getBeginLoc(), diag::err_auto_init_list_from_c);
-        return DAR_FailedAlreadyDiagnosed;
-      }
-    }
-  }
-
-  SourceLocation Loc = Init->getExprLoc();
-
-  LocalInstantiationScope InstScope(*this);
-
-  // Build template<class TemplParam> void Func(FuncParam);
-  TemplateTypeParmDecl *TemplParam = TemplateTypeParmDecl::Create(
-      Context, nullptr, SourceLocation(), Loc, Depth, 0, nullptr, false, false);
-  QualType TemplArg = QualType(TemplParam->getTypeForDecl(), 0);
-  NamedDecl *TemplParamPtr = TemplParam;
-  FixedSizeTemplateParameterListStorage<1, false> TemplateParamsSt(
-      Loc, Loc, TemplParamPtr, Loc, nullptr);
-
-  QualType FuncParam =
-      SubstituteDeducedTypeTransform(*this, TemplArg, /*UseTypeSugar*/false)
-          .Apply(Type);
-  assert(!FuncParam.isNull() &&
-         "substituting template parameter for 'auto' failed");
-
-  // Deduce type of TemplParam in Func(Init)
-  SmallVector<DeducedTemplateArgument, 1> Deduced;
-  Deduced.resize(1);
-
-  TemplateDeductionInfo Info(Loc, Depth);
-
-  // If deduction failed, don't diagnose if the initializer is dependent; it
-  // might acquire a matching type in the instantiation.
-  auto DeductionFailed = [&](TemplateDeductionResult TDK,
-                             ArrayRef<SourceRange> Ranges) -> DeduceAutoResult {
-    if (Init->isTypeDependent()) {
-      Result = SubstituteDeducedTypeTransform(*this, QualType()).Apply(Type);
-      assert(!Result.isNull() && "substituting DependentTy can't fail");
-      return DAR_Succeeded;
-    }
-    if (diagnoseAutoDeductionFailure(*this, TDK, Info, Ranges))
-      return DAR_FailedAlreadyDiagnosed;
-    return DAR_Failed;
-  };
-
-  SmallVector<OriginalCallArg, 4> OriginalCallArgs;
-
-  InitListExpr *InitList = dyn_cast<InitListExpr>(Init);
-  if (InitList) {
-    // Notionally, we substitute std::initializer_list<T> for 'auto' and deduce
-    // against that. Such deduction only succeeds if removing cv-qualifiers and
-    // references results in std::initializer_list<T>.
-    if (!Type.getType().getNonReferenceType()->getAs<AutoType>())
-      return DAR_Failed;
-
-    SourceRange DeducedFromInitRange;
-    for (unsigned i = 0, e = InitList->getNumInits(); i < e; ++i) {
-      Expr *Init = InitList->getInit(i);
-
-      if (auto TDK = DeduceTemplateArgumentsFromCallArgument(
-              *this, TemplateParamsSt.get(), 0, TemplArg, Init,
-              Info, Deduced, OriginalCallArgs, /*Decomposed*/ true,
-              /*ArgIdx*/ 0, /*TDF*/ 0))
-        return DeductionFailed(TDK, {DeducedFromInitRange,
-                                     Init->getSourceRange()});
-
-      if (DeducedFromInitRange.isInvalid() &&
-          Deduced[0].getKind() != TemplateArgument::Null)
-        DeducedFromInitRange = Init->getSourceRange();
-    }
-  } else {
-    if (!getLangOpts().CPlusPlus && Init->refersToBitField()) {
-      Diag(Loc, diag::err_auto_bitfield);
-      return DAR_FailedAlreadyDiagnosed;
-    }
-
-    if (auto TDK = DeduceTemplateArgumentsFromCallArgument(
-            *this, TemplateParamsSt.get(), 0, FuncParam, Init, Info, Deduced,
-            OriginalCallArgs, /*Decomposed*/ false, /*ArgIdx*/ 0, /*TDF*/ 0))
-      return DeductionFailed(TDK, {});
-  }
-
-  // Could be null if somehow 'auto' appears in a non-deduced context.
-  if (Deduced[0].getKind() != TemplateArgument::Type)
-    return DeductionFailed(TDK_Incomplete, {});
-
-  QualType DeducedType = Deduced[0].getAsType();
-
-  if (InitList) {
-    DeducedType = BuildStdInitializerList(DeducedType, Loc);
-    if (DeducedType.isNull())
-      return DAR_FailedAlreadyDiagnosed;
-  }
-
-  Result = SubstituteDeducedTypeTransform(*this, DeducedType).Apply(Type);
-  if (Result.isNull())
-    return DAR_FailedAlreadyDiagnosed;
-
-  // Check that the deduced argument type is compatible with the original
-  // argument type per C++ [temp.deduct.call]p4.
-  QualType DeducedA = InitList ? Deduced[0].getAsType() : Result;
-  for (const OriginalCallArg &OriginalArg : OriginalCallArgs) {
-    assert((bool)InitList == OriginalArg.DecomposedParam &&
-           "decomposed non-init-list in auto deduction?");
-    if (auto TDK =
-            CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA)) {
-      Result = QualType();
-      return DeductionFailed(TDK, {});
-    }
-  }
-
-  return DAR_Succeeded;
-}
-
-QualType Sema::SubstAutoType(QualType TypeWithAuto,
-                             QualType TypeToReplaceAuto) {
-  if (TypeToReplaceAuto->isDependentType())
-    TypeToReplaceAuto = QualType();
-  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
-      .TransformType(TypeWithAuto);
-}
-
-TypeSourceInfo *Sema::SubstAutoTypeSourceInfo(TypeSourceInfo *TypeWithAuto,
-                                              QualType TypeToReplaceAuto) {
-  if (TypeToReplaceAuto->isDependentType())
-    TypeToReplaceAuto = QualType();
-  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
-      .TransformType(TypeWithAuto);
-}
-
-QualType Sema::ReplaceAutoType(QualType TypeWithAuto,
-                               QualType TypeToReplaceAuto) {
-  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto,
-                                        /*UseTypeSugar*/ false)
-      .TransformType(TypeWithAuto);
-}
-
-void Sema::DiagnoseAutoDeductionFailure(VarDecl *VDecl, Expr *Init) {
-  if (isa<InitListExpr>(Init))
-    Diag(VDecl->getLocation(),
-         VDecl->isInitCapture()
-             ? diag::err_init_capture_deduction_failure_from_init_list
-             : diag::err_auto_var_deduction_failure_from_init_list)
-      << VDecl->getDeclName() << VDecl->getType() << Init->getSourceRange();
-  else
-    Diag(VDecl->getLocation(),
-         VDecl->isInitCapture() ? diag::err_init_capture_deduction_failure
-                                : diag::err_auto_var_deduction_failure)
-      << VDecl->getDeclName() << VDecl->getType() << Init->getType()
-      << Init->getSourceRange();
-}
-
-bool Sema::DeduceReturnType(FunctionDecl *FD, SourceLocation Loc,
-                            bool Diagnose) {
-  assert(FD->getReturnType()->isUndeducedType());
-
-  // For a lambda's conversion operator, deduce any 'auto' or 'decltype(auto)'
-  // within the return type from the call operator's type.
-  if (isLambdaConversionOperator(FD)) {
-    CXXRecordDecl *Lambda = cast<CXXMethodDecl>(FD)->getParent();
-    FunctionDecl *CallOp = Lambda->getLambdaCallOperator();
-
-    // For a generic lambda, instantiate the call operator if needed.
-    if (auto *Args = FD->getTemplateSpecializationArgs()) {
-      CallOp = InstantiateFunctionDeclaration(
-          CallOp->getDescribedFunctionTemplate(), Args, Loc);
-      if (!CallOp || CallOp->isInvalidDecl())
-        return true;
-
-      // We might need to deduce the return type by instantiating the definition
-      // of the operator() function.
-      if (CallOp->getReturnType()->isUndeducedType())
-        InstantiateFunctionDefinition(Loc, CallOp);
-    }
-
-    if (CallOp->isInvalidDecl())
-      return true;
-    assert(!CallOp->getReturnType()->isUndeducedType() &&
-           "failed to deduce lambda return type");
-
-    // Build the new return type from scratch.
-    QualType RetType = getLambdaConversionFunctionResultType(
-        CallOp->getType()->castAs<FunctionProtoType>());
-    if (FD->getReturnType()->getAs<PointerType>())
-      RetType = Context.getPointerType(RetType);
-    else {
-      assert(FD->getReturnType()->getAs<BlockPointerType>());
-      RetType = Context.getBlockPointerType(RetType);
-    }
-    Context.adjustDeducedFunctionResultType(FD, RetType);
-    return false;
-  }
-
-  if (FD->getTemplateInstantiationPattern())
-    InstantiateFunctionDefinition(Loc, FD);
-
-  bool StillUndeduced = FD->getReturnType()->isUndeducedType();
-  if (StillUndeduced && Diagnose && !FD->isInvalidDecl()) {
-    Diag(Loc, diag::err_auto_fn_used_before_defined) << FD;
-    Diag(FD->getLocation(), diag::note_callee_decl) << FD;
-  }
-
-  return StillUndeduced;
-}
-
-/// If this is a non-static member function,
-static void
-AddImplicitObjectParameterType(ASTContext &Context,
-                               CXXMethodDecl *Method,
-                               SmallVectorImpl<QualType> &ArgTypes) {
-  // C++11 [temp.func.order]p3:
-  //   [...] The new parameter is of type "reference to cv A," where cv are
-  //   the cv-qualifiers of the function template (if any) and A is
-  //   the class of which the function template is a member.
-  //
-  // The standard doesn't say explicitly, but we pick the appropriate kind of
-  // reference type based on [over.match.funcs]p4.
-  QualType ArgTy = Context.getTypeDeclType(Method->getParent());
-  ArgTy = Context.getQualifiedType(ArgTy, Method->getTypeQualifiers());
-  if (Method->getRefQualifier() == RQ_RValue)
-    ArgTy = Context.getRValueReferenceType(ArgTy);
-  else
-    ArgTy = Context.getLValueReferenceType(ArgTy);
-  ArgTypes.push_back(ArgTy);
-}
-
-/// Determine whether the function template \p FT1 is at least as
-/// specialized as \p FT2.
-static bool isAtLeastAsSpecializedAs(Sema &S,
-                                     SourceLocation Loc,
-                                     FunctionTemplateDecl *FT1,
-                                     FunctionTemplateDecl *FT2,
-                                     TemplatePartialOrderingContext TPOC,
-                                     unsigned NumCallArguments1) {
-  FunctionDecl *FD1 = FT1->getTemplatedDecl();
-  FunctionDecl *FD2 = FT2->getTemplatedDecl();
-  const FunctionProtoType *Proto1 = FD1->getType()->getAs<FunctionProtoType>();
-  const FunctionProtoType *Proto2 = FD2->getType()->getAs<FunctionProtoType>();
-
-  assert(Proto1 && Proto2 && "Function templates must have prototypes");
-  TemplateParameterList *TemplateParams = FT2->getTemplateParameters();
-  SmallVector<DeducedTemplateArgument, 4> Deduced;
-  Deduced.resize(TemplateParams->size());
-
-  // C++0x [temp.deduct.partial]p3:
-  //   The types used to determine the ordering depend on the context in which
-  //   the partial ordering is done:
-  TemplateDeductionInfo Info(Loc);
-  SmallVector<QualType, 4> Args2;
-  switch (TPOC) {
-  case TPOC_Call: {
-    //   - In the context of a function call, the function parameter types are
-    //     used.
-    CXXMethodDecl *Method1 = dyn_cast<CXXMethodDecl>(FD1);
-    CXXMethodDecl *Method2 = dyn_cast<CXXMethodDecl>(FD2);
-
-    // C++11 [temp.func.order]p3:
-    //   [...] If only one of the function templates is a non-static
-    //   member, that function template is considered to have a new
-    //   first parameter inserted in its function parameter list. The
-    //   new parameter is of type "reference to cv A," where cv are
-    //   the cv-qualifiers of the function template (if any) and A is
-    //   the class of which the function template is a member.
-    //
-    // Note that we interpret this to mean "if one of the function
-    // templates is a non-static member and the other is a non-member";
-    // otherwise, the ordering rules for static functions against non-static
-    // functions don't make any sense.
-    //
-    // C++98/03 doesn't have this provision but we've extended DR532 to cover
-    // it as wording was broken prior to it.
-    SmallVector<QualType, 4> Args1;
-
-    unsigned NumComparedArguments = NumCallArguments1;
-
-    if (!Method2 && Method1 && !Method1->isStatic()) {
-      // Compare 'this' from Method1 against first parameter from Method2.
-      AddImplicitObjectParameterType(S.Context, Method1, Args1);
-      ++NumComparedArguments;
-    } else if (!Method1 && Method2 && !Method2->isStatic()) {
-      // Compare 'this' from Method2 against first parameter from Method1.
-      AddImplicitObjectParameterType(S.Context, Method2, Args2);
-    }
-
-    Args1.insert(Args1.end(), Proto1->param_type_begin(),
-                 Proto1->param_type_end());
-    Args2.insert(Args2.end(), Proto2->param_type_begin(),
-                 Proto2->param_type_end());
-
-    // C++ [temp.func.order]p5:
-    //   The presence of unused ellipsis and default arguments has no effect on
-    //   the partial ordering of function templates.
-    if (Args1.size() > NumComparedArguments)
-      Args1.resize(NumComparedArguments);
-    if (Args2.size() > NumComparedArguments)
-      Args2.resize(NumComparedArguments);
-    if (DeduceTemplateArguments(S, TemplateParams, Args2.data(), Args2.size(),
-                                Args1.data(), Args1.size(), Info, Deduced,
-                                TDF_None, /*PartialOrdering=*/true))
-      return false;
-
-    break;
-  }
-
-  case TPOC_Conversion:
-    //   - In the context of a call to a conversion operator, the return types
-    //     of the conversion function templates are used.
-    if (DeduceTemplateArgumentsByTypeMatch(
-            S, TemplateParams, Proto2->getReturnType(), Proto1->getReturnType(),
-            Info, Deduced, TDF_None,
-            /*PartialOrdering=*/true))
-      return false;
-    break;
-
-  case TPOC_Other:
-    //   - In other contexts (14.6.6.2) the function template's function type
-    //     is used.
-    if (DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
-                                           FD2->getType(), FD1->getType(),
-                                           Info, Deduced, TDF_None,
-                                           /*PartialOrdering=*/true))
-      return false;
-    break;
-  }
-
-  // C++0x [temp.deduct.partial]p11:
-  //   In most cases, all template parameters must have values in order for
-  //   deduction to succeed, but for partial ordering purposes a template
-  //   parameter may remain without a value provided it is not used in the
-  //   types being used for partial ordering. [ Note: a template parameter used
-  //   in a non-deduced context is considered used. -end note]
-  unsigned ArgIdx = 0, NumArgs = Deduced.size();
-  for (; ArgIdx != NumArgs; ++ArgIdx)
-    if (Deduced[ArgIdx].isNull())
-      break;
-
-  // FIXME: We fail to implement [temp.deduct.type]p1 along this path. We need
-  // to substitute the deduced arguments back into the template and check that
-  // we get the right type.
-
-  if (ArgIdx == NumArgs) {
-    // All template arguments were deduced. FT1 is at least as specialized
-    // as FT2.
-    return true;
-  }
-
-  // Figure out which template parameters were used.
-  llvm::SmallBitVector UsedParameters(TemplateParams->size());
-  switch (TPOC) {
-  case TPOC_Call:
-    for (unsigned I = 0, N = Args2.size(); I != N; ++I)
-      ::MarkUsedTemplateParameters(S.Context, Args2[I], false,
-                                   TemplateParams->getDepth(),
-                                   UsedParameters);
-    break;
-
-  case TPOC_Conversion:
-    ::MarkUsedTemplateParameters(S.Context, Proto2->getReturnType(), false,
-                                 TemplateParams->getDepth(), UsedParameters);
-    break;
-
-  case TPOC_Other:
-    ::MarkUsedTemplateParameters(S.Context, FD2->getType(), false,
-                                 TemplateParams->getDepth(),
-                                 UsedParameters);
-    break;
-  }
-
-  for (; ArgIdx != NumArgs; ++ArgIdx)
-    // If this argument had no value deduced but was used in one of the types
-    // used for partial ordering, then deduction fails.
-    if (Deduced[ArgIdx].isNull() && UsedParameters[ArgIdx])
-      return false;
-
-  return true;
-}
-
-/// Determine whether this a function template whose parameter-type-list
-/// ends with a function parameter pack.
-static bool isVariadicFunctionTemplate(FunctionTemplateDecl *FunTmpl) {
-  FunctionDecl *Function = FunTmpl->getTemplatedDecl();
-  unsigned NumParams = Function->getNumParams();
-  if (NumParams == 0)
-    return false;
-
-  ParmVarDecl *Last = Function->getParamDecl(NumParams - 1);
-  if (!Last->isParameterPack())
-    return false;
-
-  // Make sure that no previous parameter is a parameter pack.
-  while (--NumParams > 0) {
-    if (Function->getParamDecl(NumParams - 1)->isParameterPack())
-      return false;
-  }
-
-  return true;
-}
-
-/// Returns the more specialized function template according
-/// to the rules of function template partial ordering (C++ [temp.func.order]).
-///
-/// \param FT1 the first function template
-///
-/// \param FT2 the second function template
-///
-/// \param TPOC the context in which we are performing partial ordering of
-/// function templates.
-///
-/// \param NumCallArguments1 The number of arguments in the call to FT1, used
-/// only when \c TPOC is \c TPOC_Call.
-///
-/// \param NumCallArguments2 The number of arguments in the call to FT2, used
-/// only when \c TPOC is \c TPOC_Call.
-///
-/// \returns the more specialized function template. If neither
-/// template is more specialized, returns NULL.
-FunctionTemplateDecl *
-Sema::getMoreSpecializedTemplate(FunctionTemplateDecl *FT1,
-                                 FunctionTemplateDecl *FT2,
-                                 SourceLocation Loc,
-                                 TemplatePartialOrderingContext TPOC,
-                                 unsigned NumCallArguments1,
-                                 unsigned NumCallArguments2) {
-  bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC,
-                                          NumCallArguments1);
-  bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC,
-                                          NumCallArguments2);
-
-  if (Better1 != Better2) // We have a clear winner
-    return Better1 ? FT1 : FT2;
-
-  if (!Better1 && !Better2) // Neither is better than the other
-    return nullptr;
-
-  // FIXME: This mimics what GCC implements, but doesn't match up with the
-  // proposed resolution for core issue 692. This area needs to be sorted out,
-  // but for now we attempt to maintain compatibility.
-  bool Variadic1 = isVariadicFunctionTemplate(FT1);
-  bool Variadic2 = isVariadicFunctionTemplate(FT2);
-  if (Variadic1 != Variadic2)
-    return Variadic1? FT2 : FT1;
-
-  return nullptr;
-}
-
-/// Determine if the two templates are equivalent.
-static bool isSameTemplate(TemplateDecl *T1, TemplateDecl *T2) {
-  if (T1 == T2)
-    return true;
-
-  if (!T1 || !T2)
-    return false;
-
-  return T1->getCanonicalDecl() == T2->getCanonicalDecl();
-}
-
-/// Retrieve the most specialized of the given function template
-/// specializations.
-///
-/// \param SpecBegin the start iterator of the function template
-/// specializations that we will be comparing.
-///
-/// \param SpecEnd the end iterator of the function template
-/// specializations, paired with \p SpecBegin.
-///
-/// \param Loc the location where the ambiguity or no-specializations
-/// diagnostic should occur.
-///
-/// \param NoneDiag partial diagnostic used to diagnose cases where there are
-/// no matching candidates.
-///
-/// \param AmbigDiag partial diagnostic used to diagnose an ambiguity, if one
-/// occurs.
-///
-/// \param CandidateDiag partial diagnostic used for each function template
-/// specialization that is a candidate in the ambiguous ordering. One parameter
-/// in this diagnostic should be unbound, which will correspond to the string
-/// describing the template arguments for the function template specialization.
-///
-/// \returns the most specialized function template specialization, if
-/// found. Otherwise, returns SpecEnd.
-UnresolvedSetIterator Sema::getMostSpecialized(
-    UnresolvedSetIterator SpecBegin, UnresolvedSetIterator SpecEnd,
-    TemplateSpecCandidateSet &FailedCandidates,
-    SourceLocation Loc, const PartialDiagnostic &NoneDiag,
-    const PartialDiagnostic &AmbigDiag, const PartialDiagnostic &CandidateDiag,
-    bool Complain, QualType TargetType) {
-  if (SpecBegin == SpecEnd) {
-    if (Complain) {
-      Diag(Loc, NoneDiag);
-      FailedCandidates.NoteCandidates(*this, Loc);
-    }
-    return SpecEnd;
-  }
-
-  if (SpecBegin + 1 == SpecEnd)
-    return SpecBegin;
-
-  // Find the function template that is better than all of the templates it
-  // has been compared to.
-  UnresolvedSetIterator Best = SpecBegin;
-  FunctionTemplateDecl *BestTemplate
-    = cast<FunctionDecl>(*Best)->getPrimaryTemplate();
-  assert(BestTemplate && "Not a function template specialization?");
-  for (UnresolvedSetIterator I = SpecBegin + 1; I != SpecEnd; ++I) {
-    FunctionTemplateDecl *Challenger
-      = cast<FunctionDecl>(*I)->getPrimaryTemplate();
-    assert(Challenger && "Not a function template specialization?");
-    if (isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
-                                                  Loc, TPOC_Other, 0, 0),
-                       Challenger)) {
-      Best = I;
-      BestTemplate = Challenger;
-    }
-  }
-
-  // Make sure that the "best" function template is more specialized than all
-  // of the others.
-  bool Ambiguous = false;
-  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
-    FunctionTemplateDecl *Challenger
-      = cast<FunctionDecl>(*I)->getPrimaryTemplate();
-    if (I != Best &&
-        !isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
-                                                   Loc, TPOC_Other, 0, 0),
-                        BestTemplate)) {
-      Ambiguous = true;
-      break;
-    }
-  }
-
-  if (!Ambiguous) {
-    // We found an answer. Return it.
-    return Best;
-  }
-
-  // Diagnose the ambiguity.
-  if (Complain) {
-    Diag(Loc, AmbigDiag);
-
-    // FIXME: Can we order the candidates in some sane way?
-    for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
-      PartialDiagnostic PD = CandidateDiag;
-      const auto *FD = cast<FunctionDecl>(*I);
-      PD << FD << getTemplateArgumentBindingsText(
-                      FD->getPrimaryTemplate()->getTemplateParameters(),
-                      *FD->getTemplateSpecializationArgs());
-      if (!TargetType.isNull())
-        HandleFunctionTypeMismatch(PD, FD->getType(), TargetType);
-      Diag((*I)->getLocation(), PD);
-    }
-  }
-
-  return SpecEnd;
-}
-
-/// Determine whether one partial specialization, P1, is at least as
-/// specialized than another, P2.
-///
-/// \tparam TemplateLikeDecl The kind of P2, which must be a
-/// TemplateDecl or {Class,Var}TemplatePartialSpecializationDecl.
-/// \param T1 The injected-class-name of P1 (faked for a variable template).
-/// \param T2 The injected-class-name of P2 (faked for a variable template).
-template<typename TemplateLikeDecl>
-static bool isAtLeastAsSpecializedAs(Sema &S, QualType T1, QualType T2,
-                                     TemplateLikeDecl *P2,
-                                     TemplateDeductionInfo &Info) {
-  // C++ [temp.class.order]p1:
-  //   For two class template partial specializations, the first is at least as
-  //   specialized as the second if, given the following rewrite to two
-  //   function templates, the first function template is at least as
-  //   specialized as the second according to the ordering rules for function
-  //   templates (14.6.6.2):
-  //     - the first function template has the same template parameters as the
-  //       first partial specialization and has a single function parameter
-  //       whose type is a class template specialization with the template
-  //       arguments of the first partial specialization, and
-  //     - the second function template has the same template parameters as the
-  //       second partial specialization and has a single function parameter
-  //       whose type is a class template specialization with the template
-  //       arguments of the second partial specialization.
-  //
-  // Rather than synthesize function templates, we merely perform the
-  // equivalent partial ordering by performing deduction directly on
-  // the template arguments of the class template partial
-  // specializations. This computation is slightly simpler than the
-  // general problem of function template partial ordering, because
-  // class template partial specializations are more constrained. We
-  // know that every template parameter is deducible from the class
-  // template partial specialization's template arguments, for
-  // example.
-  SmallVector<DeducedTemplateArgument, 4> Deduced;
-
-  // Determine whether P1 is at least as specialized as P2.
-  Deduced.resize(P2->getTemplateParameters()->size());
-  if (DeduceTemplateArgumentsByTypeMatch(S, P2->getTemplateParameters(),
-                                         T2, T1, Info, Deduced, TDF_None,
-                                         /*PartialOrdering=*/true))
-    return false;
-
-  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(),
-                                               Deduced.end());
-  Sema::InstantiatingTemplate Inst(S, Info.getLocation(), P2, DeducedArgs,
-                                   Info);
-  auto *TST1 = T1->castAs<TemplateSpecializationType>();
-  if (FinishTemplateArgumentDeduction(
-          S, P2, /*PartialOrdering=*/true,
-          TemplateArgumentList(TemplateArgumentList::OnStack,
-                               TST1->template_arguments()),
-          Deduced, Info))
-    return false;
-
-  return true;
-}
-
-/// Returns the more specialized class template partial specialization
-/// according to the rules of partial ordering of class template partial
-/// specializations (C++ [temp.class.order]).
-///
-/// \param PS1 the first class template partial specialization
-///
-/// \param PS2 the second class template partial specialization
-///
-/// \returns the more specialized class template partial specialization. If
-/// neither partial specialization is more specialized, returns NULL.
-ClassTemplatePartialSpecializationDecl *
-Sema::getMoreSpecializedPartialSpecialization(
-                                  ClassTemplatePartialSpecializationDecl *PS1,
-                                  ClassTemplatePartialSpecializationDecl *PS2,
-                                              SourceLocation Loc) {
-  QualType PT1 = PS1->getInjectedSpecializationType();
-  QualType PT2 = PS2->getInjectedSpecializationType();
-
-  TemplateDeductionInfo Info(Loc);
-  bool Better1 = isAtLeastAsSpecializedAs(*this, PT1, PT2, PS2, Info);
-  bool Better2 = isAtLeastAsSpecializedAs(*this, PT2, PT1, PS1, Info);
-
-  if (Better1 == Better2)
-    return nullptr;
-
-  return Better1 ? PS1 : PS2;
-}
-
-bool Sema::isMoreSpecializedThanPrimary(
-    ClassTemplatePartialSpecializationDecl *Spec, TemplateDeductionInfo &Info) {
-  ClassTemplateDecl *Primary = Spec->getSpecializedTemplate();
-  QualType PrimaryT = Primary->getInjectedClassNameSpecialization();
-  QualType PartialT = Spec->getInjectedSpecializationType();
-  if (!isAtLeastAsSpecializedAs(*this, PartialT, PrimaryT, Primary, Info))
-    return false;
-  if (isAtLeastAsSpecializedAs(*this, PrimaryT, PartialT, Spec, Info)) {
-    Info.clearSFINAEDiagnostic();
-    return false;
-  }
-  return true;
-}
-
-VarTemplatePartialSpecializationDecl *
-Sema::getMoreSpecializedPartialSpecialization(
-    VarTemplatePartialSpecializationDecl *PS1,
-    VarTemplatePartialSpecializationDecl *PS2, SourceLocation Loc) {
-  // Pretend the variable template specializations are class template
-  // specializations and form a fake injected class name type for comparison.
-  assert(PS1->getSpecializedTemplate() == PS2->getSpecializedTemplate() &&
-         "the partial specializations being compared should specialize"
-         " the same template.");
-  TemplateName Name(PS1->getSpecializedTemplate());
-  TemplateName CanonTemplate = Context.getCanonicalTemplateName(Name);
-  QualType PT1 = Context.getTemplateSpecializationType(
-      CanonTemplate, PS1->getTemplateArgs().asArray());
-  QualType PT2 = Context.getTemplateSpecializationType(
-      CanonTemplate, PS2->getTemplateArgs().asArray());
-
-  TemplateDeductionInfo Info(Loc);
-  bool Better1 = isAtLeastAsSpecializedAs(*this, PT1, PT2, PS2, Info);
-  bool Better2 = isAtLeastAsSpecializedAs(*this, PT2, PT1, PS1, Info);
-
-  if (Better1 == Better2)
-    return nullptr;
-
-  return Better1 ? PS1 : PS2;
-}
-
-bool Sema::isMoreSpecializedThanPrimary(
-    VarTemplatePartialSpecializationDecl *Spec, TemplateDeductionInfo &Info) {
-  TemplateDecl *Primary = Spec->getSpecializedTemplate();
-  // FIXME: Cache the injected template arguments rather than recomputing
-  // them for each partial specialization.
-  SmallVector<TemplateArgument, 8> PrimaryArgs;
-  Context.getInjectedTemplateArgs(Primary->getTemplateParameters(),
-                                  PrimaryArgs);
-
-  TemplateName CanonTemplate =
-      Context.getCanonicalTemplateName(TemplateName(Primary));
-  QualType PrimaryT = Context.getTemplateSpecializationType(
-      CanonTemplate, PrimaryArgs);
-  QualType PartialT = Context.getTemplateSpecializationType(
-      CanonTemplate, Spec->getTemplateArgs().asArray());
-  if (!isAtLeastAsSpecializedAs(*this, PartialT, PrimaryT, Primary, Info))
-    return false;
-  if (isAtLeastAsSpecializedAs(*this, PrimaryT, PartialT, Spec, Info)) {
-    Info.clearSFINAEDiagnostic();
-    return false;
-  }
-  return true;
-}
-
-bool Sema::isTemplateTemplateParameterAtLeastAsSpecializedAs(
-     TemplateParameterList *P, TemplateDecl *AArg, SourceLocation Loc) {
-  // C++1z [temp.arg.template]p4: (DR 150)
-  //   A template template-parameter P is at least as specialized as a
-  //   template template-argument A if, given the following rewrite to two
-  //   function templates...
-
-  // Rather than synthesize function templates, we merely perform the
-  // equivalent partial ordering by performing deduction directly on
-  // the template parameter lists of the template template parameters.
-  //
-  //   Given an invented class template X with the template parameter list of
-  //   A (including default arguments):
-  TemplateName X = Context.getCanonicalTemplateName(TemplateName(AArg));
-  TemplateParameterList *A = AArg->getTemplateParameters();
-
-  //    - Each function template has a single function parameter whose type is
-  //      a specialization of X with template arguments corresponding to the
-  //      template parameters from the respective function template
-  SmallVector<TemplateArgument, 8> AArgs;
-  Context.getInjectedTemplateArgs(A, AArgs);
-
-  // Check P's arguments against A's parameter list. This will fill in default
-  // template arguments as needed. AArgs are already correct by construction.
-  // We can't just use CheckTemplateIdType because that will expand alias
-  // templates.
-  SmallVector<TemplateArgument, 4> PArgs;
-  {
-    SFINAETrap Trap(*this);
-
-    Context.getInjectedTemplateArgs(P, PArgs);
-    TemplateArgumentListInfo PArgList(P->getLAngleLoc(), P->getRAngleLoc());
-    for (unsigned I = 0, N = P->size(); I != N; ++I) {
-      // Unwrap packs that getInjectedTemplateArgs wrapped around pack
-      // expansions, to form an "as written" argument list.
-      TemplateArgument Arg = PArgs[I];
-      if (Arg.getKind() == TemplateArgument::Pack) {
-        assert(Arg.pack_size() == 1 && Arg.pack_begin()->isPackExpansion());
-        Arg = *Arg.pack_begin();
-      }
-      PArgList.addArgument(getTrivialTemplateArgumentLoc(
-          Arg, QualType(), P->getParam(I)->getLocation()));
-    }
-    PArgs.clear();
-
-    // C++1z [temp.arg.template]p3:
-    //   If the rewrite produces an invalid type, then P is not at least as
-    //   specialized as A.
-    if (CheckTemplateArgumentList(AArg, Loc, PArgList, false, PArgs) ||
-        Trap.hasErrorOccurred())
-      return false;
-  }
-
-  QualType AType = Context.getTemplateSpecializationType(X, AArgs);
-  QualType PType = Context.getTemplateSpecializationType(X, PArgs);
-
-  //   ... the function template corresponding to P is at least as specialized
-  //   as the function template corresponding to A according to the partial
-  //   ordering rules for function templates.
-  TemplateDeductionInfo Info(Loc, A->getDepth());
-  return isAtLeastAsSpecializedAs(*this, PType, AType, AArg, Info);
-}
-
-/// Mark the template parameters that are used by the given
-/// expression.
-static void
-MarkUsedTemplateParameters(ASTContext &Ctx,
-                           const Expr *E,
-                           bool OnlyDeduced,
-                           unsigned Depth,
-                           llvm::SmallBitVector &Used) {
-  // We can deduce from a pack expansion.
-  if (const PackExpansionExpr *Expansion = dyn_cast<PackExpansionExpr>(E))
-    E = Expansion->getPattern();
-
-  // Skip through any implicit casts we added while type-checking, and any
-  // substitutions performed by template alias expansion.
-  while (true) {
-    if (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E))
-      E = ICE->getSubExpr();
-    else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(E))
-      E = CE->getSubExpr();
-    else if (const SubstNonTypeTemplateParmExpr *Subst =
-               dyn_cast<SubstNonTypeTemplateParmExpr>(E))
-      E = Subst->getReplacement();
-    else
-      break;
-  }
-
-  // FIXME: if !OnlyDeduced, we have to walk the whole subexpression to
-  // find other occurrences of template parameters.
-  const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E);
-  if (!DRE)
-    return;
-
-  const NonTypeTemplateParmDecl *NTTP
-    = dyn_cast<NonTypeTemplateParmDecl>(DRE->getDecl());
-  if (!NTTP)
-    return;
-
-  if (NTTP->getDepth() == Depth)
-    Used[NTTP->getIndex()] = true;
-
-  // In C++17 mode, additional arguments may be deduced from the type of a
-  // non-type argument.
-  if (Ctx.getLangOpts().CPlusPlus17)
-    MarkUsedTemplateParameters(Ctx, NTTP->getType(), OnlyDeduced, Depth, Used);
-}
-
-/// Mark the template parameters that are used by the given
-/// nested name specifier.
-static void
-MarkUsedTemplateParameters(ASTContext &Ctx,
-                           NestedNameSpecifier *NNS,
-                           bool OnlyDeduced,
-                           unsigned Depth,
-                           llvm::SmallBitVector &Used) {
-  if (!NNS)
-    return;
-
-  MarkUsedTemplateParameters(Ctx, NNS->getPrefix(), OnlyDeduced, Depth,
-                             Used);
-  MarkUsedTemplateParameters(Ctx, QualType(NNS->getAsType(), 0),
-                             OnlyDeduced, Depth, Used);
-}
-
-/// Mark the template parameters that are used by the given
-/// template name.
-static void
-MarkUsedTemplateParameters(ASTContext &Ctx,
-                           TemplateName Name,
-                           bool OnlyDeduced,
-                           unsigned Depth,
-                           llvm::SmallBitVector &Used) {
-  if (TemplateDecl *Template = Name.getAsTemplateDecl()) {
-    if (TemplateTemplateParmDecl *TTP
-          = dyn_cast<TemplateTemplateParmDecl>(Template)) {
-      if (TTP->getDepth() == Depth)
-        Used[TTP->getIndex()] = true;
-    }
-    return;
-  }
-
-  if (QualifiedTemplateName *QTN = Name.getAsQualifiedTemplateName())
-    MarkUsedTemplateParameters(Ctx, QTN->getQualifier(), OnlyDeduced,
-                               Depth, Used);
-  if (DependentTemplateName *DTN = Name.getAsDependentTemplateName())
-    MarkUsedTemplateParameters(Ctx, DTN->getQualifier(), OnlyDeduced,
-                               Depth, Used);
-}
-
-/// Mark the template parameters that are used by the given
-/// type.
-static void
-MarkUsedTemplateParameters(ASTContext &Ctx, QualType T,
-                           bool OnlyDeduced,
-                           unsigned Depth,
-                           llvm::SmallBitVector &Used) {
-  if (T.isNull())
-    return;
-
-  // Non-dependent types have nothing deducible
-  if (!T->isDependentType())
-    return;
-
-  T = Ctx.getCanonicalType(T);
-  switch (T->getTypeClass()) {
-  case Type::Pointer:
-    MarkUsedTemplateParameters(Ctx,
-                               cast<PointerType>(T)->getPointeeType(),
-                               OnlyDeduced,
-                               Depth,
-                               Used);
-    break;
-
-  case Type::BlockPointer:
-    MarkUsedTemplateParameters(Ctx,
-                               cast<BlockPointerType>(T)->getPointeeType(),
-                               OnlyDeduced,
-                               Depth,
-                               Used);
-    break;
-
-  case Type::LValueReference:
-  case Type::RValueReference:
-    MarkUsedTemplateParameters(Ctx,
-                               cast<ReferenceType>(T)->getPointeeType(),
-                               OnlyDeduced,
-                               Depth,
-                               Used);
-    break;
-
-  case Type::MemberPointer: {
-    const MemberPointerType *MemPtr = cast<MemberPointerType>(T.getTypePtr());
-    MarkUsedTemplateParameters(Ctx, MemPtr->getPointeeType(), OnlyDeduced,
-                               Depth, Used);
-    MarkUsedTemplateParameters(Ctx, QualType(MemPtr->getClass(), 0),
-                               OnlyDeduced, Depth, Used);
-    break;
-  }
-
-  case Type::DependentSizedArray:
-    MarkUsedTemplateParameters(Ctx,
-                               cast<DependentSizedArrayType>(T)->getSizeExpr(),
-                               OnlyDeduced, Depth, Used);
-    // Fall through to check the element type
-    LLVM_FALLTHROUGH;
-
-  case Type::ConstantArray:
-  case Type::IncompleteArray:
-    MarkUsedTemplateParameters(Ctx,
-                               cast<ArrayType>(T)->getElementType(),
-                               OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::Vector:
-  case Type::ExtVector:
-    MarkUsedTemplateParameters(Ctx,
-                               cast<VectorType>(T)->getElementType(),
-                               OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::DependentVector: {
-    const auto *VecType = cast<DependentVectorType>(T);
-    MarkUsedTemplateParameters(Ctx, VecType->getElementType(), OnlyDeduced,
-                               Depth, Used);
-    MarkUsedTemplateParameters(Ctx, VecType->getSizeExpr(), OnlyDeduced, Depth,
-                               Used);
-    break;
-  }
-  case Type::DependentSizedExtVector: {
-    const DependentSizedExtVectorType *VecType
-      = cast<DependentSizedExtVectorType>(T);
-    MarkUsedTemplateParameters(Ctx, VecType->getElementType(), OnlyDeduced,
-                               Depth, Used);
-    MarkUsedTemplateParameters(Ctx, VecType->getSizeExpr(), OnlyDeduced,
-                               Depth, Used);
-    break;
-  }
-
-  case Type::DependentAddressSpace: {
-    const DependentAddressSpaceType *DependentASType =
-        cast<DependentAddressSpaceType>(T);
-    MarkUsedTemplateParameters(Ctx, DependentASType->getPointeeType(),
-                               OnlyDeduced, Depth, Used);
-    MarkUsedTemplateParameters(Ctx,
-                               DependentASType->getAddrSpaceExpr(),
-                               OnlyDeduced, Depth, Used);
-    break;
-  }
-
-  case Type::FunctionProto: {
-    const FunctionProtoType *Proto = cast<FunctionProtoType>(T);
-    MarkUsedTemplateParameters(Ctx, Proto->getReturnType(), OnlyDeduced, Depth,
-                               Used);
-    for (unsigned I = 0, N = Proto->getNumParams(); I != N; ++I) {
-      // C++17 [temp.deduct.type]p5:
-      //   The non-deduced contexts are: [...]
-      //   -- A function parameter pack that does not occur at the end of the
-      //      parameter-declaration-list.
-      if (!OnlyDeduced || I + 1 == N ||
-          !Proto->getParamType(I)->getAs<PackExpansionType>()) {
-        MarkUsedTemplateParameters(Ctx, Proto->getParamType(I), OnlyDeduced,
-                                   Depth, Used);
-      } else {
-        // FIXME: C++17 [temp.deduct.call]p1:
-        //   When a function parameter pack appears in a non-deduced context,
-        //   the type of that pack is never deduced.
-        //
-        // We should also track a set of "never deduced" parameters, and
-        // subtract that from the list of deduced parameters after marking.
-      }
-    }
-    if (auto *E = Proto->getNoexceptExpr())
-      MarkUsedTemplateParameters(Ctx, E, OnlyDeduced, Depth, Used);
-    break;
-  }
-
-  case Type::TemplateTypeParm: {
-    const TemplateTypeParmType *TTP = cast<TemplateTypeParmType>(T);
-    if (TTP->getDepth() == Depth)
-      Used[TTP->getIndex()] = true;
-    break;
-  }
-
-  case Type::SubstTemplateTypeParmPack: {
-    const SubstTemplateTypeParmPackType *Subst
-      = cast<SubstTemplateTypeParmPackType>(T);
-    MarkUsedTemplateParameters(Ctx,
-                               QualType(Subst->getReplacedParameter(), 0),
-                               OnlyDeduced, Depth, Used);
-    MarkUsedTemplateParameters(Ctx, Subst->getArgumentPack(),
-                               OnlyDeduced, Depth, Used);
-    break;
-  }
-
-  case Type::InjectedClassName:
-    T = cast<InjectedClassNameType>(T)->getInjectedSpecializationType();
-    LLVM_FALLTHROUGH;
-
-  case Type::TemplateSpecialization: {
-    const TemplateSpecializationType *Spec
-      = cast<TemplateSpecializationType>(T);
-    MarkUsedTemplateParameters(Ctx, Spec->getTemplateName(), OnlyDeduced,
-                               Depth, Used);
-
-    // C++0x [temp.deduct.type]p9:
-    //   If the template argument list of P contains a pack expansion that is
-    //   not the last template argument, the entire template argument list is a
-    //   non-deduced context.
-    if (OnlyDeduced &&
-        hasPackExpansionBeforeEnd(Spec->template_arguments()))
-      break;
-
-    for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
-      MarkUsedTemplateParameters(Ctx, Spec->getArg(I), OnlyDeduced, Depth,
-                                 Used);
-    break;
-  }
-
-  case Type::Complex:
-    if (!OnlyDeduced)
-      MarkUsedTemplateParameters(Ctx,
-                                 cast<ComplexType>(T)->getElementType(),
-                                 OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::Atomic:
-    if (!OnlyDeduced)
-      MarkUsedTemplateParameters(Ctx,
-                                 cast<AtomicType>(T)->getValueType(),
-                                 OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::DependentName:
-    if (!OnlyDeduced)
-      MarkUsedTemplateParameters(Ctx,
-                                 cast<DependentNameType>(T)->getQualifier(),
-                                 OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::DependentTemplateSpecialization: {
-    // C++14 [temp.deduct.type]p5:
-    //   The non-deduced contexts are:
-    //     -- The nested-name-specifier of a type that was specified using a
-    //        qualified-id
-    //
-    // C++14 [temp.deduct.type]p6:
-    //   When a type name is specified in a way that includes a non-deduced
-    //   context, all of the types that comprise that type name are also
-    //   non-deduced.
-    if (OnlyDeduced)
-      break;
-
-    const DependentTemplateSpecializationType *Spec
-      = cast<DependentTemplateSpecializationType>(T);
-
-    MarkUsedTemplateParameters(Ctx, Spec->getQualifier(),
-                               OnlyDeduced, Depth, Used);
-
-    for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
-      MarkUsedTemplateParameters(Ctx, Spec->getArg(I), OnlyDeduced, Depth,
-                                 Used);
-    break;
-  }
-
-  case Type::TypeOf:
-    if (!OnlyDeduced)
-      MarkUsedTemplateParameters(Ctx,
-                                 cast<TypeOfType>(T)->getUnderlyingType(),
-                                 OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::TypeOfExpr:
-    if (!OnlyDeduced)
-      MarkUsedTemplateParameters(Ctx,
-                                 cast<TypeOfExprType>(T)->getUnderlyingExpr(),
-                                 OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::Decltype:
-    if (!OnlyDeduced)
-      MarkUsedTemplateParameters(Ctx,
-                                 cast<DecltypeType>(T)->getUnderlyingExpr(),
-                                 OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::UnaryTransform:
-    if (!OnlyDeduced)
-      MarkUsedTemplateParameters(Ctx,
-                                 cast<UnaryTransformType>(T)->getUnderlyingType(),
-                                 OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::PackExpansion:
-    MarkUsedTemplateParameters(Ctx,
-                               cast<PackExpansionType>(T)->getPattern(),
-                               OnlyDeduced, Depth, Used);
-    break;
-
-  case Type::Auto:
-  case Type::DeducedTemplateSpecialization:
-    MarkUsedTemplateParameters(Ctx,
-                               cast<DeducedType>(T)->getDeducedType(),
-                               OnlyDeduced, Depth, Used);
-    break;
-
-  // None of these types have any template parameters in them.
-  case Type::Builtin:
-  case Type::VariableArray:
-  case Type::FunctionNoProto:
-  case Type::Record:
-  case Type::Enum:
-  case Type::ObjCInterface:
-  case Type::ObjCObject:
-  case Type::ObjCObjectPointer:
-  case Type::UnresolvedUsing:
-  case Type::Pipe:
-#define TYPE(Class, Base)
-#define ABSTRACT_TYPE(Class, Base)
-#define DEPENDENT_TYPE(Class, Base)
-#define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
-#include "clang/AST/TypeNodes.def"
-    break;
-  }
-}
-
-/// Mark the template parameters that are used by this
-/// template argument.
-static void
-MarkUsedTemplateParameters(ASTContext &Ctx,
-                           const TemplateArgument &TemplateArg,
-                           bool OnlyDeduced,
-                           unsigned Depth,
-                           llvm::SmallBitVector &Used) {
-  switch (TemplateArg.getKind()) {
-  case TemplateArgument::Null:
-  case TemplateArgument::Integral:
-  case TemplateArgument::Declaration:
-    break;
-
-  case TemplateArgument::NullPtr:
-    MarkUsedTemplateParameters(Ctx, TemplateArg.getNullPtrType(), OnlyDeduced,
-                               Depth, Used);
-    break;
-
-  case TemplateArgument::Type:
-    MarkUsedTemplateParameters(Ctx, TemplateArg.getAsType(), OnlyDeduced,
-                               Depth, Used);
-    break;
-
-  case TemplateArgument::Template:
-  case TemplateArgument::TemplateExpansion:
-    MarkUsedTemplateParameters(Ctx,
-                               TemplateArg.getAsTemplateOrTemplatePattern(),
-                               OnlyDeduced, Depth, Used);
-    break;
-
-  case TemplateArgument::Expression:
-    MarkUsedTemplateParameters(Ctx, TemplateArg.getAsExpr(), OnlyDeduced,
-                               Depth, Used);
-    break;
-
-  case TemplateArgument::Pack:
-    for (const auto &P : TemplateArg.pack_elements())
-      MarkUsedTemplateParameters(Ctx, P, OnlyDeduced, Depth, Used);
-    break;
-  }
-}
-
-/// Mark which template parameters can be deduced from a given
-/// template argument list.
-///
-/// \param TemplateArgs the template argument list from which template
-/// parameters will be deduced.
-///
-/// \param Used a bit vector whose elements will be set to \c true
-/// to indicate when the corresponding template parameter will be
-/// deduced.
-void
-Sema::MarkUsedTemplateParameters(const TemplateArgumentList &TemplateArgs,
-                                 bool OnlyDeduced, unsigned Depth,
-                                 llvm::SmallBitVector &Used) {
-  // C++0x [temp.deduct.type]p9:
-  //   If the template argument list of P contains a pack expansion that is not
-  //   the last template argument, the entire template argument list is a
-  //   non-deduced context.
-  if (OnlyDeduced &&
-      hasPackExpansionBeforeEnd(TemplateArgs.asArray()))
-    return;
-
-  for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
-    ::MarkUsedTemplateParameters(Context, TemplateArgs[I], OnlyDeduced,
-                                 Depth, Used);
-}
-
-/// Marks all of the template parameters that will be deduced by a
-/// call to the given function template.
-void Sema::MarkDeducedTemplateParameters(
-    ASTContext &Ctx, const FunctionTemplateDecl *FunctionTemplate,
-    llvm::SmallBitVector &Deduced) {
-  TemplateParameterList *TemplateParams
-    = FunctionTemplate->getTemplateParameters();
-  Deduced.clear();
-  Deduced.resize(TemplateParams->size());
-
-  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
-  for (unsigned I = 0, N = Function->getNumParams(); I != N; ++I)
-    ::MarkUsedTemplateParameters(Ctx, Function->getParamDecl(I)->getType(),
-                                 true, TemplateParams->getDepth(), Deduced);
-}
-
-bool hasDeducibleTemplateParameters(Sema &S,
-                                    FunctionTemplateDecl *FunctionTemplate,
-                                    QualType T) {
-  if (!T->isDependentType())
-    return false;
-
-  TemplateParameterList *TemplateParams
-    = FunctionTemplate->getTemplateParameters();
-  llvm::SmallBitVector Deduced(TemplateParams->size());
-  ::MarkUsedTemplateParameters(S.Context, T, true, TemplateParams->getDepth(),
-                               Deduced);
-
-  return Deduced.any();
-}