diff mbox series

[v19,24/40] c++: Implement __is_function built-in trait

Message ID 20231013223957.1634024-25-kmatsui@gcc.gnu.org
State Unresolved
Headers
Series Optimize type traits performance |

Checks

Context Check Description
snail/gcc-patch-check warning Git am fail log

Commit Message

Ken Matsui Oct. 13, 2023, 10:37 p.m. UTC 
  This patch implements built-in trait for std::is_function.

gcc/cp/ChangeLog:

	* cp-trait.def: Define __is_function.
	* cp-trait.gperf: Reflect cp-trait.def change.
	* cp-trait.h: Likewise.
	* constraint.cc (diagnose_trait_expr): Handle CPTK_IS_FUNCTION.
	* semantics.cc (trait_expr_value): Likewise.
	(finish_trait_expr): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/has-builtin-1.C: Test existence of __is_function.
	* g++.dg/ext/is_function.C: New test.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 gcc/cp/constraint.cc                     |   3 +
 gcc/cp/cp-trait.def                      |   1 +
 gcc/cp/cp-trait.gperf                    |   1 +
 gcc/cp/cp-trait.h                        | 143 ++++++++++++-----------
 gcc/cp/semantics.cc                      |   4 +
 gcc/testsuite/g++.dg/ext/has-builtin-1.C |   3 +
 gcc/testsuite/g++.dg/ext/is_function.C   |  58 +++++++++
 7 files changed, 143 insertions(+), 70 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_function.C
diff mbox series

Patch

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 5cdb59d174e..99a7e7247ce 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3750,6 +3750,9 @@  diagnose_trait_expr (tree expr, tree args)
     case CPTK_IS_FINAL:
       inform (loc, "  %qT is not a final class", t1);
       break;
+    case CPTK_IS_FUNCTION:
+      inform (loc, "  %qT is not a function", t1);
+      break;
     case CPTK_IS_LAYOUT_COMPATIBLE:
       inform (loc, "  %qT is not layout compatible with %qT", t1, t2);
       break;
diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index e867d9c4c47..fa79bc0c68c 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -70,6 +70,7 @@  DEFTRAIT_EXPR (IS_CONVERTIBLE, "__is_convertible", 2)
 DEFTRAIT_EXPR (IS_EMPTY, "__is_empty", 1)
 DEFTRAIT_EXPR (IS_ENUM, "__is_enum", 1)
 DEFTRAIT_EXPR (IS_FINAL, "__is_final", 1)
+DEFTRAIT_EXPR (IS_FUNCTION, "__is_function", 1)
 DEFTRAIT_EXPR (IS_LAYOUT_COMPATIBLE, "__is_layout_compatible", 2)
 DEFTRAIT_EXPR (IS_LITERAL_TYPE, "__is_literal_type", 1)
 DEFTRAIT_EXPR (IS_MEMBER_FUNCTION_POINTER, "__is_member_function_pointer", 1)
diff --git a/gcc/cp/cp-trait.gperf b/gcc/cp/cp-trait.gperf
index 5989b84727f..771242a7f45 100644
--- a/gcc/cp/cp-trait.gperf
+++ b/gcc/cp/cp-trait.gperf
@@ -50,6 +50,7 @@  struct cp_trait {
 "__is_empty", CPTK_IS_EMPTY, 1, false
 "__is_enum", CPTK_IS_ENUM, 1, false
 "__is_final", CPTK_IS_FINAL, 1, false
+"__is_function", CPTK_IS_FUNCTION, 1, false
 "__is_layout_compatible", CPTK_IS_LAYOUT_COMPATIBLE, 2, false
 "__is_literal_type", CPTK_IS_LITERAL_TYPE, 1, false
 "__is_member_function_pointer", CPTK_IS_MEMBER_FUNCTION_POINTER, 1, false
diff --git a/gcc/cp/cp-trait.h b/gcc/cp/cp-trait.h
index f0b4f96d4a9..b6db58e93c9 100644
--- a/gcc/cp/cp-trait.h
+++ b/gcc/cp/cp-trait.h
@@ -54,7 +54,7 @@  struct cp_trait {
   short arity;
   bool type;
 };
-/* maximum key range = 94, duplicates = 0 */
+/* maximum key range = 109, duplicates = 0 */
 
 class cp_trait_lookup
 {
@@ -69,32 +69,32 @@  cp_trait_lookup::hash (const char *str, size_t len)
 {
   static const unsigned char asso_values[] =
     {
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101,  20, 101,  40,   5,  40,
-       40,   0,  60,  10, 101,   0, 101, 101,   5,  25,
-       30,   0,   5, 101,  10,  15,   5,   0,  25, 101,
-      101,  20, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101, 101, 101, 101, 101,
-      101, 101, 101, 101, 101, 101
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116,  20, 116,  40,   5,  40,
+       50,   0,  55,  10, 116,   0, 116, 116,   5,  25,
+       30,   0,   5, 116,  10,  15,   5,   0,  25, 116,
+      116,  20, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116, 116, 116, 116, 116,
+      116, 116, 116, 116, 116, 116
     };
   unsigned int hval = len;
 
@@ -116,113 +116,113 @@  cp_trait_lookup::find (const char *str, size_t len)
 {
   enum
     {
-      TOTAL_KEYWORDS = 55,
+      TOTAL_KEYWORDS = 56,
       MIN_WORD_LENGTH = 7,
       MAX_WORD_LENGTH = 37,
       MIN_HASH_VALUE = 7,
-      MAX_HASH_VALUE = 100
+      MAX_HASH_VALUE = 115
     };
 
   static const struct cp_trait wordlist[] =
     {
-#line 83 "../../gcc/cp/cp-trait.gperf"
+#line 84 "../../gcc/cp/cp-trait.gperf"
       {"__bases", CPTK_BASES, 1, true},
 #line 51 "../../gcc/cp/cp-trait.gperf"
       {"__is_enum", CPTK_IS_ENUM, 1, false},
-#line 73 "../../gcc/cp/cp-trait.gperf"
+#line 74 "../../gcc/cp/cp-trait.gperf"
       {"__is_union", CPTK_IS_UNION, 1, false},
-#line 77 "../../gcc/cp/cp-trait.gperf"
-      {"__remove_cv", CPTK_REMOVE_CV, 1, true},
 #line 78 "../../gcc/cp/cp-trait.gperf"
+      {"__remove_cv", CPTK_REMOVE_CV, 1, true},
+#line 79 "../../gcc/cp/cp-trait.gperf"
       {"__remove_cvref", CPTK_REMOVE_CVREF, 1, true},
 #line 50 "../../gcc/cp/cp-trait.gperf"
       {"__is_empty", CPTK_IS_EMPTY, 1, false},
-#line 68 "../../gcc/cp/cp-trait.gperf"
+#line 69 "../../gcc/cp/cp-trait.gperf"
       {"__is_trivial", CPTK_IS_TRIVIAL, 1, false},
-#line 79 "../../gcc/cp/cp-trait.gperf"
+#line 80 "../../gcc/cp/cp-trait.gperf"
       {"__remove_reference", CPTK_REMOVE_REFERENCE, 1, true},
-#line 84 "../../gcc/cp/cp-trait.gperf"
+#line 85 "../../gcc/cp/cp-trait.gperf"
       {"__direct_bases", CPTK_DIRECT_BASES, 1, true},
-#line 81 "../../gcc/cp/cp-trait.gperf"
+#line 82 "../../gcc/cp/cp-trait.gperf"
       {"__underlying_type", CPTK_UNDERLYING_TYPE, 1, true},
 #line 45 "../../gcc/cp/cp-trait.gperf"
       {"__is_bounded_array", CPTK_IS_BOUNDED_ARRAY, 1, false},
-#line 80 "../../gcc/cp/cp-trait.gperf"
+#line 81 "../../gcc/cp/cp-trait.gperf"
       {"__type_pack_element", CPTK_TYPE_PACK_ELEMENT, -1, true},
-#line 72 "../../gcc/cp/cp-trait.gperf"
+#line 73 "../../gcc/cp/cp-trait.gperf"
       {"__is_unbounded_array", CPTK_IS_UNBOUNDED_ARRAY, 1, false},
-#line 63 "../../gcc/cp/cp-trait.gperf"
+#line 64 "../../gcc/cp/cp-trait.gperf"
       {"__is_polymorphic", CPTK_IS_POLYMORPHIC, 1, false},
-#line 54 "../../gcc/cp/cp-trait.gperf"
+#line 55 "../../gcc/cp/cp-trait.gperf"
       {"__is_literal_type", CPTK_IS_LITERAL_TYPE, 1, false},
-#line 71 "../../gcc/cp/cp-trait.gperf"
+#line 72 "../../gcc/cp/cp-trait.gperf"
       {"__is_trivially_copyable", CPTK_IS_TRIVIALLY_COPYABLE, 1, false},
-#line 69 "../../gcc/cp/cp-trait.gperf"
+#line 70 "../../gcc/cp/cp-trait.gperf"
       {"__is_trivially_assignable", CPTK_IS_TRIVIALLY_ASSIGNABLE, 2, false},
-#line 66 "../../gcc/cp/cp-trait.gperf"
+#line 67 "../../gcc/cp/cp-trait.gperf"
       {"__is_scoped_enum", CPTK_IS_SCOPED_ENUM, 1, false},
 #line 44 "../../gcc/cp/cp-trait.gperf"
       {"__is_base_of", CPTK_IS_BASE_OF, 2, false},
-#line 70 "../../gcc/cp/cp-trait.gperf"
+#line 71 "../../gcc/cp/cp-trait.gperf"
       {"__is_trivially_constructible", CPTK_IS_TRIVIALLY_CONSTRUCTIBLE, -1, false},
-#line 76 "../../gcc/cp/cp-trait.gperf"
+#line 77 "../../gcc/cp/cp-trait.gperf"
       {"__reference_converts_from_temporary", CPTK_REF_CONVERTS_FROM_TEMPORARY, 2, false},
-#line 75 "../../gcc/cp/cp-trait.gperf"
+#line 76 "../../gcc/cp/cp-trait.gperf"
       {"__reference_constructs_from_temporary", CPTK_REF_CONSTRUCTS_FROM_TEMPORARY, 2, false},
 #line 33 "../../gcc/cp/cp-trait.gperf"
       {"__has_nothrow_copy", CPTK_HAS_NOTHROW_COPY, 1, false},
 #line 31 "../../gcc/cp/cp-trait.gperf"
       {"__has_nothrow_assign", CPTK_HAS_NOTHROW_ASSIGN, 1, false},
-#line 61 "../../gcc/cp/cp-trait.gperf"
+#line 62 "../../gcc/cp/cp-trait.gperf"
       {"__is_pointer_interconvertible_base_of", CPTK_IS_POINTER_INTERCONVERTIBLE_BASE_OF, 2, false},
-#line 74 "../../gcc/cp/cp-trait.gperf"
+#line 75 "../../gcc/cp/cp-trait.gperf"
       {"__is_volatile", CPTK_IS_VOLATILE, 1, false},
 #line 39 "../../gcc/cp/cp-trait.gperf"
       {"__has_virtual_destructor", CPTK_HAS_VIRTUAL_DESTRUCTOR, 1, false},
 #line 32 "../../gcc/cp/cp-trait.gperf"
       {"__has_nothrow_constructor", CPTK_HAS_NOTHROW_CONSTRUCTOR, 1, false},
-#line 53 "../../gcc/cp/cp-trait.gperf"
+#line 54 "../../gcc/cp/cp-trait.gperf"
       {"__is_layout_compatible", CPTK_IS_LAYOUT_COMPATIBLE, 2, false},
 #line 36 "../../gcc/cp/cp-trait.gperf"
       {"__has_trivial_copy", CPTK_HAS_TRIVIAL_COPY, 1, false},
-#line 65 "../../gcc/cp/cp-trait.gperf"
+#line 66 "../../gcc/cp/cp-trait.gperf"
       {"__is_same", CPTK_IS_SAME, 2, false},
 #line 34 "../../gcc/cp/cp-trait.gperf"
       {"__has_trivial_assign", CPTK_HAS_TRIVIAL_ASSIGN, 1, false},
 #line 30 "../../gcc/cp/cp-trait.gperf"
       {"__is_same_as", CPTK_IS_SAME, 2, false},
-#line 62 "../../gcc/cp/cp-trait.gperf"
-      {"__is_pod", CPTK_IS_POD, 1, false},
 #line 37 "../../gcc/cp/cp-trait.gperf"
       {"__has_trivial_destructor", CPTK_HAS_TRIVIAL_DESTRUCTOR, 1, false},
 #line 35 "../../gcc/cp/cp-trait.gperf"
       {"__has_trivial_constructor", CPTK_HAS_TRIVIAL_CONSTRUCTOR, 1, false},
-#line 58 "../../gcc/cp/cp-trait.gperf"
+#line 59 "../../gcc/cp/cp-trait.gperf"
       {"__is_nothrow_assignable", CPTK_IS_NOTHROW_ASSIGNABLE, 2, false},
-#line 60 "../../gcc/cp/cp-trait.gperf"
+#line 61 "../../gcc/cp/cp-trait.gperf"
       {"__is_nothrow_convertible", CPTK_IS_NOTHROW_CONVERTIBLE, 2, false},
 #line 42 "../../gcc/cp/cp-trait.gperf"
       {"__is_array", CPTK_IS_ARRAY, 1, false},
-#line 59 "../../gcc/cp/cp-trait.gperf"
+#line 60 "../../gcc/cp/cp-trait.gperf"
       {"__is_nothrow_constructible", CPTK_IS_NOTHROW_CONSTRUCTIBLE, -1, false},
+#line 63 "../../gcc/cp/cp-trait.gperf"
+      {"__is_pod", CPTK_IS_POD, 1, false},
 #line 41 "../../gcc/cp/cp-trait.gperf"
       {"__is_aggregate", CPTK_IS_AGGREGATE, 1, false},
 #line 40 "../../gcc/cp/cp-trait.gperf"
       {"__is_abstract", CPTK_IS_ABSTRACT, 1, false},
-#line 57 "../../gcc/cp/cp-trait.gperf"
+#line 58 "../../gcc/cp/cp-trait.gperf"
       {"__is_member_pointer", CPTK_IS_MEMBER_POINTER, 1, false},
 #line 43 "../../gcc/cp/cp-trait.gperf"
       {"__is_assignable", CPTK_IS_ASSIGNABLE, 2, false},
-#line 67 "../../gcc/cp/cp-trait.gperf"
+#line 68 "../../gcc/cp/cp-trait.gperf"
       {"__is_standard_layout", CPTK_IS_STD_LAYOUT, 1, false},
-#line 56 "../../gcc/cp/cp-trait.gperf"
+#line 57 "../../gcc/cp/cp-trait.gperf"
       {"__is_member_object_pointer", CPTK_IS_MEMBER_OBJECT_POINTER, 1, false},
-#line 55 "../../gcc/cp/cp-trait.gperf"
+#line 56 "../../gcc/cp/cp-trait.gperf"
       {"__is_member_function_pointer", CPTK_IS_MEMBER_FUNCTION_POINTER, 1, false},
+#line 65 "../../gcc/cp/cp-trait.gperf"
+      {"__is_reference", CPTK_IS_REFERENCE, 1, false},
 #line 47 "../../gcc/cp/cp-trait.gperf"
       {"__is_const", CPTK_IS_CONST, 1, false},
-#line 64 "../../gcc/cp/cp-trait.gperf"
-      {"__is_reference", CPTK_IS_REFERENCE, 1, false},
 #line 38 "../../gcc/cp/cp-trait.gperf"
       {"__has_unique_object_representations", CPTK_HAS_UNIQUE_OBJ_REPRESENTATIONS, 1, false},
 #line 49 "../../gcc/cp/cp-trait.gperf"
@@ -231,10 +231,12 @@  cp_trait_lookup::find (const char *str, size_t len)
       {"__is_constructible", CPTK_IS_CONSTRUCTIBLE, -1, false},
 #line 46 "../../gcc/cp/cp-trait.gperf"
       {"__is_class", CPTK_IS_CLASS, 1, false},
-#line 82 "../../gcc/cp/cp-trait.gperf"
-      {"__is_deducible ", CPTK_IS_DEDUCIBLE, 2, false},
 #line 52 "../../gcc/cp/cp-trait.gperf"
-      {"__is_final", CPTK_IS_FINAL, 1, false}
+      {"__is_final", CPTK_IS_FINAL, 1, false},
+#line 53 "../../gcc/cp/cp-trait.gperf"
+      {"__is_function", CPTK_IS_FUNCTION, 1, false},
+#line 83 "../../gcc/cp/cp-trait.gperf"
+      {"__is_deducible ", CPTK_IS_DEDUCIBLE, 2, false}
     };
 
   static const signed char lookup[] =
@@ -242,11 +244,12 @@  cp_trait_lookup::find (const char *str, size_t len)
       -1, -1, -1, -1, -1, -1, -1,  0, -1,  1,  2,  3, -1, -1,
        4,  5, -1,  6,  7,  8, -1, -1,  9, 10, 11, 12, 13, 14,
       15, -1, 16, 17, 18, 19, -1, 20, -1, 21, 22, -1, 23, -1,
-      24, 25, 26, 27, -1, 28, 29, 30, 31, -1, 32, 33, 34, 35,
-      -1, -1, 36, 37, 38, 39, -1, -1, 40, -1, -1, -1, 41, 42,
-      43, -1, -1, -1, -1, 44, 45, -1, 46, -1, 47, -1, -1, -1,
-      48, 49, 50, -1, 51, -1, 52, -1, -1, -1, -1, 53, -1, -1,
-      -1, -1, 54
+      24, 25, 26, 27, -1, 28, 29, 30, 31, -1, 32, -1, 33, 34,
+      -1, -1, 35, 36, 37, 38, -1, 39, 40, -1, -1, -1, 41, 42,
+      43, -1, -1, -1, -1, 44, 45, -1, 46, 47, 48, -1, -1, -1,
+      -1, 49, 50, -1, 51, -1, 52, -1, -1, -1, -1, 53, -1, -1,
+      54, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, 55
     };
 
   if (len <= MAX_WORD_LENGTH && len >= MIN_WORD_LENGTH)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index df720459458..4b8e80f3e62 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12178,6 +12178,9 @@  trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_FINAL:
       return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
 
+    case CPTK_IS_FUNCTION:
+      return type_code1 == FUNCTION_TYPE;
+
     case CPTK_IS_LAYOUT_COMPATIBLE:
       return layout_compatible_type_p (type1, type2);
 
@@ -12405,6 +12408,7 @@  finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_CLASS:
     case CPTK_IS_CONST:
     case CPTK_IS_ENUM:
+    case CPTK_IS_FUNCTION:
     case CPTK_IS_MEMBER_FUNCTION_POINTER:
     case CPTK_IS_MEMBER_OBJECT_POINTER:
     case CPTK_IS_MEMBER_POINTER:
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index e112d317657..4d3947572a4 100644
--- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
+++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
@@ -89,6 +89,9 @@ 
 #if !__has_builtin (__is_final)
 # error "__has_builtin (__is_final) failed"
 #endif
+#if !__has_builtin (__is_function)
+# error "__has_builtin (__is_function) failed"
+#endif
 #if !__has_builtin (__is_layout_compatible)
 # error "__has_builtin (__is_layout_compatible) failed"
 #endif
diff --git a/gcc/testsuite/g++.dg/ext/is_function.C b/gcc/testsuite/g++.dg/ext/is_function.C
new file mode 100644
index 00000000000..2e1594b12ad
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_function.C
@@ -0,0 +1,58 @@ 
+// { dg-do compile { target c++11 } }
+
+#include <testsuite_tr1.h>
+
+using namespace __gnu_test;
+
+#define SA(X) static_assert((X),#X)
+#define SA_TEST_CATEGORY(TRAIT, TYPE, EXPECT)	\
+  SA(TRAIT(TYPE) == EXPECT);					\
+  SA(TRAIT(const TYPE) == EXPECT);				\
+  SA(TRAIT(volatile TYPE) == EXPECT);			\
+  SA(TRAIT(const volatile TYPE) == EXPECT)
+
+struct A
+{ void fn(); };
+
+template<typename>
+struct AHolder { };
+
+template<class T, class U>
+struct AHolder<U T::*>
+{ using type = U; };
+
+// Positive tests.
+SA(__is_function(int (int)));
+SA(__is_function(ClassType (ClassType)));
+SA(__is_function(float (int, float, int[], int&)));
+SA(__is_function(int (int, ...)));
+SA(__is_function(bool (ClassType) const));
+SA(__is_function(AHolder<decltype(&A::fn)>::type));
+
+void fn();
+SA(__is_function(decltype(fn)));
+
+// Negative tests.
+SA_TEST_CATEGORY(__is_function, int, false);
+SA_TEST_CATEGORY(__is_function, int*, false);
+SA_TEST_CATEGORY(__is_function, int&, false);
+SA_TEST_CATEGORY(__is_function, void, false);
+SA_TEST_CATEGORY(__is_function, void*, false);
+SA_TEST_CATEGORY(__is_function, void**, false);
+SA_TEST_CATEGORY(__is_function, std::nullptr_t, false);
+
+SA_TEST_CATEGORY(__is_function, AbstractClass, false);
+SA(!__is_function(int(&)(int)));
+SA(!__is_function(int(*)(int)));
+
+SA_TEST_CATEGORY(__is_function, A, false);
+SA_TEST_CATEGORY(__is_function, decltype(&A::fn), false);
+
+struct FnCallOverload
+{ void operator()(); };
+SA_TEST_CATEGORY(__is_function, FnCallOverload, false);
+
+// Sanity check.
+SA_TEST_CATEGORY(__is_function, ClassType, false);
+SA_TEST_CATEGORY(__is_function, IncompleteClass, false);
+SA_TEST_CATEGORY(__is_function, IncompleteUnion, false);