Logically, the following are are type names - just like .Vt,

some of them with an optional variable name following:
- .Ft
- .Fa in the SYNOPSIS
- .Fn second and later arguments in the SYNOPSIS
So add these to the .Vt macro table in the mandoc.db(5) database.
During my LibreSSL work, i'm getting really tired of typing
$ man -k Vt,Ft,Fa=some_type_name
over and over again; now, this becomes just:
$ man -k Vt=some_type_name

2 files changed, 35 insertions, 8 deletions

diff --git a/regress/usr.bin/mandoc/db/out/fn.dout b/regress/usr.bin/mandoc/db/out/fn.dout
index d7048d7dc29..2d6732bd217 100644
--- a/regress/usr.bin/mandoc/db/out/fn.dout
+++ b/regress/usr.bin/mandoc/db/out/fn.dout
@@ -1,7 +1,7 @@
 initial magic 0x3a7d0cdb
 version       0x00000001
 macros offset 0x00000078
-end offset    0x0000022c
+end offset    0x0000028c
 page count    1
 === PAGES ===
 page name # [f]fn # [1t]Fn # [s]fn_func # [s]fo_name 
@@ -57,7 +57,13 @@ macro 30 entry count 0
 macro 31 entry count 0
 macro 32 entry count 0
 macro 33 entry count 0
-macro 34 entry count 0
+macro 34 entry count 4
+=== MACRO 34 ===
+macro 34 # fn_arg # fn 
+macro 34 # fn_type # fn 
+macro 34 # fo_arg # fn 
+macro 34 # fo_type # fn 
+=== END OF MACRO 34 ===
 macro 35 entry count 0
 === END OF MACROS ===
 final magic   0x3a7d0cdb
diff --git a/usr.bin/mandoc/mandocdb.c b/usr.bin/mandoc/mandocdb.c
index 0e16fd39775..00a0cdf0b53 100644
--- a/usr.bin/mandoc/mandocdb.c
+++ b/usr.bin/mandoc/mandocdb.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mandocdb.c,v 1.206 2018/02/07 20:31:32 schwarze Exp $ */
+/*	$OpenBSD: mandocdb.c,v 1.207 2018/02/23 18:24:41 schwarze Exp $ */
 /*
  * Copyright (c) 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2011-2017 Ingo Schwarze <schwarze@openbsd.org>
@@ -124,6 +124,8 @@ static	void	 parse_mdoc(struct mpage *, const struct roff_meta *,
 			const struct roff_node *);
 static	int	 parse_mdoc_head(struct mpage *, const struct roff_meta *,
 			const struct roff_node *);
+static	int	 parse_mdoc_Fa(struct mpage *, const struct roff_meta *,
+			const struct roff_node *);
 static	int	 parse_mdoc_Fd(struct mpage *, const struct roff_meta *,
 			const struct roff_node *);
 static	void	 parse_mdoc_fname(struct mpage *, const struct roff_node *);
@@ -192,11 +194,11 @@ static	const struct mdoc_handler __mdocs[MDOC_MAX - MDOC_Dd] = {
 	{ NULL, TYPE_Er, 0 },  /* Er */
 	{ NULL, TYPE_Ev, 0 },  /* Ev */
 	{ NULL, 0, 0 },  /* Ex */
-	{ NULL, TYPE_Fa, 0 },  /* Fa */
+	{ parse_mdoc_Fa, 0, 0 },  /* Fa */
 	{ parse_mdoc_Fd, 0, 0 },  /* Fd */
 	{ NULL, TYPE_Fl, 0 },  /* Fl */
 	{ parse_mdoc_Fn, 0, 0 },  /* Fn */
-	{ NULL, TYPE_Ft, 0 },  /* Ft */
+	{ NULL, TYPE_Ft | TYPE_Vt, 0 },  /* Ft */
 	{ NULL, TYPE_Ic, 0 },  /* Ic */
 	{ NULL, TYPE_In, 0 },  /* In */
 	{ NULL, TYPE_Li, 0 },  /* Li */
@@ -1535,6 +1537,20 @@ parse_mdoc(struct mpage *mpage, const struct roff_meta *meta,
 }
 
 static int
+parse_mdoc_Fa(struct mpage *mpage, const struct roff_meta *meta,
+	const struct roff_node *n)
+{
+	uint64_t mask;
+
+	mask = TYPE_Fa;
+	if (n->sec == SEC_SYNOPSIS)
+		mask |= TYPE_Vt;
+
+	putmdockey(mpage, n->child, mask, 0);
+	return 0;
+}
+
+static int
 parse_mdoc_Fd(struct mpage *mpage, const struct roff_meta *meta,
 	const struct roff_node *n)
 {
@@ -1603,15 +1619,20 @@ static int
 parse_mdoc_Fn(struct mpage *mpage, const struct roff_meta *meta,
 	const struct roff_node *n)
 {
+	uint64_t mask;
 
 	if (n->child == NULL)
 		return 0;
 
 	parse_mdoc_fname(mpage, n->child);
 
-	for (n = n->child->next; n != NULL; n = n->next)
-		if (n->type == ROFFT_TEXT)
-			putkey(mpage, n->string, TYPE_Fa);
+	n = n->child->next;
+	if (n != NULL && n->type == ROFFT_TEXT) {
+		mask = TYPE_Fa;
+		if (n->sec == SEC_SYNOPSIS)
+			mask |= TYPE_Vt;
+		putmdockey(mpage, n, mask, 0);
+	}
 
 	return 0;
 }