From: Jason Merrill <jason@redhat.com>
Date: Tue, 8 Mar 2016 22:30:44 +0000 (-0500)
Subject: Remove Concepts from -std=c++1z.
X-Git-Tag: basepoints/gcc-7~523
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=80aac5c82043b6f3d7b2100e1f2f9abbbad97e89;p=thirdparty%2Fgcc.git

Remove Concepts from -std=c++1z.

gcc/c-family/
	* c-opts.c (set_std_cxx1z): Don't enable concepts.
gcc/testsuite/
	* lib/g++-dg.exp (g++-dg-runtest): Handle "concepts" in std list.
	* lib/target-supports.exp (check_effective_target_concepts): New.
gcc/cp/
	* parser.c (cp_parser_diagnose_invalid_type_name): Give helpful
	diagnostic for use of "concept".
	(cp_parser_requires_clause_opt): And "requires".
	(cp_parser_type_parameter, cp_parser_late_return_type_opt)
	(cp_parser_explicit_template_declaration): Adjust.
	* Make-lang.in (check-c++-all): Add "concepts" to std list.

From-SVN: r234069
---

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index f285c8b62be6..464297b65391 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,7 @@
+2016-03-08  Jason Merrill  <jason@redhat.com>
+
+	* c-opts.c (set_std_cxx1z): Don't enable concepts.
+
 2016-03-04  David Malcolm  <dmalcolm@redhat.com>
 
 	PR c/68187
diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
index c2783f7e5603..fec58bcf91f4 100644
--- a/gcc/c-family/c-opts.c
+++ b/gcc/c-family/c-opts.c
@@ -1566,8 +1566,6 @@ set_std_cxx1z (int iso)
   /* C++11 includes the C99 standard library.  */
   flag_isoc94 = 1;
   flag_isoc99 = 1;
-  /* Enable concepts by default. */
-  flag_concepts = 1;
   flag_isoc11 = 1;
   cxx_dialect = cxx1z;
   lang_hooks.name = "GNU C++14"; /* Pretend C++14 till standarization.  */
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 2b95036f931c..4bb43db6bf10 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,12 @@
 2016-03-08  Jason Merrill  <jason@redhat.com>
 
+	* parser.c (cp_parser_diagnose_invalid_type_name): Give helpful
+	diagnostic for use of "concept".
+	(cp_parser_requires_clause_opt): And "requires".
+	(cp_parser_type_parameter, cp_parser_late_return_type_opt)
+	(cp_parser_explicit_template_declaration): Adjust.
+	* Make-lang.in (check-c++-all): Add "concepts" to std list.
+
 	P0036R0: Unary Folds and Empty Parameter Packs
 	* pt.c (expand_empty_fold): Remove special cases for *,+,&,|.
 
diff --git a/gcc/cp/Make-lang.in b/gcc/cp/Make-lang.in
index 2286c64a8fb4..8770f6ff1bed 100644
--- a/gcc/cp/Make-lang.in
+++ b/gcc/cp/Make-lang.in
@@ -152,7 +152,7 @@ check-c++1z:
 
 # Run the testsuite in all standard conformance levels.
 check-c++-all:
-	$(MAKE) RUNTESTFLAGS="$(RUNTESTFLAGS) --stds=98,11,14,1z" check-g++
+	$(MAKE) RUNTESTFLAGS="$(RUNTESTFLAGS) --stds=98,11,14,1z,concepts" check-g++
 
 # Run the testsuite with garbage collection at every opportunity.
 check-g++-strict-gc:
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 535052f97d01..726d5fc6a82c 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -3172,6 +3172,8 @@ cp_parser_diagnose_invalid_type_name (cp_parser *parser, tree id,
 	       && !strcmp (IDENTIFIER_POINTER (id), "thread_local"))
 	inform (location, "C++11 %<thread_local%> only available with "
 		"-std=c++11 or -std=gnu++11");
+      else if (!flag_concepts && id == ridpointers[(int)RID_CONCEPT])
+	inform (location, "%<concept%> only available with -fconcepts");
       else if (processing_template_decl && current_class_type
 	       && TYPE_BINFO (current_class_type))
 	{
@@ -14668,13 +14670,10 @@ cp_parser_type_parameter (cp_parser* parser, bool *is_parameter_pack)
 	cp_parser_require (parser, CPP_GREATER, RT_GREATER);
 
         // If template requirements are present, parse them.
-	if (flag_concepts)
-          {
-            tree reqs = get_shorthand_constraints (current_template_parms);
-            if (tree r = cp_parser_requires_clause_opt (parser))
-              reqs = conjoin_constraints (reqs, make_predicate_constraint (r));
-            TEMPLATE_PARMS_CONSTRAINTS (current_template_parms) = reqs;
-          }
+	tree reqs = get_shorthand_constraints (current_template_parms);
+	if (tree r = cp_parser_requires_clause_opt (parser))
+	  reqs = conjoin_constraints (reqs, make_predicate_constraint (r));
+	TEMPLATE_PARMS_CONSTRAINTS (current_template_parms) = reqs;
 
 	/* Look for the `class' or 'typename' keywords.  */
 	cp_parser_type_parameter_key (parser);
@@ -19745,6 +19744,8 @@ cp_parser_late_return_type_opt (cp_parser* parser, cp_declarator *declarator,
   /* A late-specified return type is indicated by an initial '->'. */
   if (token->type != CPP_DEREF
       && token->keyword != RID_REQUIRES
+      && !(token->type == CPP_NAME
+	   && token->u.value == ridpointers[RID_REQUIRES])
       && !(declare_simd_p || cilk_simd_fn_vector_p || oacc_routine_p))
     return NULL_TREE;
 
@@ -24216,8 +24217,20 @@ cp_parser_requires_clause (cp_parser *parser)
 static tree
 cp_parser_requires_clause_opt (cp_parser *parser)
 {
-  if (!cp_lexer_next_token_is_keyword (parser->lexer, RID_REQUIRES))
-    return NULL_TREE;
+  cp_token *tok = cp_lexer_peek_token (parser->lexer);
+  if (tok->keyword != RID_REQUIRES)
+    {
+      if (!flag_concepts && tok->type == CPP_NAME
+	  && tok->u.value == ridpointers[RID_REQUIRES])
+	{
+	  error_at (cp_lexer_peek_token (parser->lexer)->location,
+		    "%<requires%> only available with -fconcepts");
+	  /* Parse and discard the requires-clause.  */
+	  cp_lexer_consume_token (parser->lexer);
+	  cp_parser_requires_clause (parser);
+	}
+      return NULL_TREE;
+    }
   cp_lexer_consume_token (parser->lexer);
   return cp_parser_requires_clause (parser);
 }
@@ -25608,13 +25621,10 @@ cp_parser_explicit_template_declaration (cp_parser* parser, bool member_p)
   cp_parser_skip_to_end_of_template_parameter_list (parser);
 
   /* Manage template requirements */
-  if (flag_concepts)
-  {
-    tree reqs = get_shorthand_constraints (current_template_parms);
-    if (tree r = cp_parser_requires_clause_opt (parser))
-      reqs = conjoin_constraints (reqs, make_predicate_constraint (r));
-    TEMPLATE_PARMS_CONSTRAINTS (current_template_parms) = reqs;
-  }
+  tree reqs = get_shorthand_constraints (current_template_parms);
+  if (tree r = cp_parser_requires_clause_opt (parser))
+    reqs = conjoin_constraints (reqs, make_predicate_constraint (r));
+  TEMPLATE_PARMS_CONSTRAINTS (current_template_parms) = reqs;
 
   cp_parser_template_declaration_after_parameters (parser, parameter_list,
 						   member_p);
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 62c70d51e064..9580c10fc451 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -2238,6 +2238,16 @@ return value even without this option.  In all other cases, when
 exhaustion is signalled by throwing @code{std::bad_alloc}.  See also
 @samp{new (nothrow)}.
 
+@item -fconcepts
+@opindex fconcepts
+Enable support for the C++ Extensions for Concepts Technical
+Specification, ISO 19217 (2015), which allows code like
+
+@smallexample
+template <class T> concept bool Addable = requires (T t) @{ t + t; @};
+template <Addable T> T add (T a, T b) @{ return a + b; @}
+@end smallexample
+
 @item -fconstexpr-depth=@var{n}
 @opindex fconstexpr-depth
 Set the maximum nested evaluation depth for C++11 constexpr functions
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 51494140033f..40e9b5275caf 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-03-08  Jason Merrill  <jason@redhat.com>
+
+	* lib/g++-dg.exp (g++-dg-runtest): Handle "concepts" in std list.
+	* lib/target-supports.exp (check_effective_target_concepts): New.
+
 2016-03-08  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/70135
diff --git a/gcc/testsuite/g++.dg/concepts/alias1.C b/gcc/testsuite/g++.dg/concepts/alias1.C
index 03b3ceae9281..fdd54bd2af15 100644
--- a/gcc/testsuite/g++.dg/concepts/alias1.C
+++ b/gcc/testsuite/g++.dg/concepts/alias1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/alias2.C b/gcc/testsuite/g++.dg/concepts/alias2.C
index d81188ed4354..7879d4419617 100644
--- a/gcc/testsuite/g++.dg/concepts/alias2.C
+++ b/gcc/testsuite/g++.dg/concepts/alias2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/alias3.C b/gcc/testsuite/g++.dg/concepts/alias3.C
index e6ab66976a16..a8f0f67e04f9 100644
--- a/gcc/testsuite/g++.dg/concepts/alias3.C
+++ b/gcc/testsuite/g++.dg/concepts/alias3.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/alias4.C b/gcc/testsuite/g++.dg/concepts/alias4.C
index 4227a44c042b..8ffa0a10e3f0 100644
--- a/gcc/testsuite/g++.dg/concepts/alias4.C
+++ b/gcc/testsuite/g++.dg/concepts/alias4.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/auto1.C b/gcc/testsuite/g++.dg/concepts/auto1.C
index 6068e4cc4862..be9237d69fa5 100644
--- a/gcc/testsuite/g++.dg/concepts/auto1.C
+++ b/gcc/testsuite/g++.dg/concepts/auto1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T1, class T2> class A { };
 
diff --git a/gcc/testsuite/g++.dg/concepts/auto3.C b/gcc/testsuite/g++.dg/concepts/auto3.C
index 1cface77d555..e1a4d7342aa4 100644
--- a/gcc/testsuite/g++.dg/concepts/auto3.C
+++ b/gcc/testsuite/g++.dg/concepts/auto3.C
@@ -1,4 +1,4 @@
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class...> class tuple {};
 
diff --git a/gcc/testsuite/g++.dg/concepts/class.C b/gcc/testsuite/g++.dg/concepts/class.C
index ea74a54da6c1..061105756cb0 100644
--- a/gcc/testsuite/g++.dg/concepts/class.C
+++ b/gcc/testsuite/g++.dg/concepts/class.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Class() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/class1.C b/gcc/testsuite/g++.dg/concepts/class1.C
index b213cb58b7e3..a2c4f5d1aed8 100644
--- a/gcc/testsuite/g++.dg/concepts/class1.C
+++ b/gcc/testsuite/g++.dg/concepts/class1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/class2.C b/gcc/testsuite/g++.dg/concepts/class2.C
index 2c3ea4483abc..4b8706d8001b 100644
--- a/gcc/testsuite/g++.dg/concepts/class2.C
+++ b/gcc/testsuite/g++.dg/concepts/class2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/class3.C b/gcc/testsuite/g++.dg/concepts/class3.C
index e3a1d2a949b6..c25c801f1f63 100644
--- a/gcc/testsuite/g++.dg/concepts/class3.C
+++ b/gcc/testsuite/g++.dg/concepts/class3.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/class4.C b/gcc/testsuite/g++.dg/concepts/class4.C
index 7ba825085523..af6db2509dbf 100644
--- a/gcc/testsuite/g++.dg/concepts/class4.C
+++ b/gcc/testsuite/g++.dg/concepts/class4.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Class() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/class5.C b/gcc/testsuite/g++.dg/concepts/class5.C
index 903bf2499558..218ec9f5a9f0 100644
--- a/gcc/testsuite/g++.dg/concepts/class5.C
+++ b/gcc/testsuite/g++.dg/concepts/class5.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool One() { return sizeof(T) >= 4; }
diff --git a/gcc/testsuite/g++.dg/concepts/class6.C b/gcc/testsuite/g++.dg/concepts/class6.C
index fe6b42d5557e..4a3a3d70a85c 100644
--- a/gcc/testsuite/g++.dg/concepts/class6.C
+++ b/gcc/testsuite/g++.dg/concepts/class6.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool One() { return sizeof(T) >= 4; }
diff --git a/gcc/testsuite/g++.dg/concepts/constrained-parm.C b/gcc/testsuite/g++.dg/concepts/constrained-parm.C
index fd21c43a037b..2650caeb9c42 100644
--- a/gcc/testsuite/g++.dg/concepts/constrained-parm.C
+++ b/gcc/testsuite/g++.dg/concepts/constrained-parm.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/decl-diagnose.C b/gcc/testsuite/g++.dg/concepts/decl-diagnose.C
index 67b56f962d0f..9829ba1ba697 100644
--- a/gcc/testsuite/g++.dg/concepts/decl-diagnose.C
+++ b/gcc/testsuite/g++.dg/concepts/decl-diagnose.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 typedef concept int CINT; // { dg-error "'concept' cannot appear in a typedef declaration" }
 
diff --git a/gcc/testsuite/g++.dg/concepts/deduction-constraint1.C b/gcc/testsuite/g++.dg/concepts/deduction-constraint1.C
index 6ff3be94ba98..dfb0c6e94367 100644
--- a/gcc/testsuite/g++.dg/concepts/deduction-constraint1.C
+++ b/gcc/testsuite/g++.dg/concepts/deduction-constraint1.C
@@ -1,5 +1,5 @@
 // PR c++/67007
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class U>
 concept bool A =
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic1.C b/gcc/testsuite/g++.dg/concepts/diagnostic1.C
index 7c360cc3943b..aa98ffa752a4 100644
--- a/gcc/testsuite/g++.dg/concepts/diagnostic1.C
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic1.C
@@ -1,5 +1,5 @@
 // PR c++/67159
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T>
 concept bool R = requires (T& t) {
diff --git a/gcc/testsuite/g++.dg/concepts/disjunction1.C b/gcc/testsuite/g++.dg/concepts/disjunction1.C
index f67fa0beacb0..24472cc296de 100644
--- a/gcc/testsuite/g++.dg/concepts/disjunction1.C
+++ b/gcc/testsuite/g++.dg/concepts/disjunction1.C
@@ -1,5 +1,5 @@
 // PR c++/66962
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <typename> struct remove_cv;
 template <typename> struct is_reference;
diff --git a/gcc/testsuite/g++.dg/concepts/dr1430.C b/gcc/testsuite/g++.dg/concepts/dr1430.C
index 7f857fe4ecc0..3a7ba0363b1a 100644
--- a/gcc/testsuite/g++.dg/concepts/dr1430.C
+++ b/gcc/testsuite/g++.dg/concepts/dr1430.C
@@ -1,5 +1,5 @@
 // PR c++/66092
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <type_traits>
 
diff --git a/gcc/testsuite/g++.dg/concepts/equiv.C b/gcc/testsuite/g++.dg/concepts/equiv.C
index c2ac7410f010..11e232fe2d5e 100644
--- a/gcc/testsuite/g++.dg/concepts/equiv.C
+++ b/gcc/testsuite/g++.dg/concepts/equiv.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Check equivalence of short- and longhand declarations.
 
diff --git a/gcc/testsuite/g++.dg/concepts/equiv2.C b/gcc/testsuite/g++.dg/concepts/equiv2.C
index 675fe2105f19..24d419b2ed3e 100644
--- a/gcc/testsuite/g++.dg/concepts/equiv2.C
+++ b/gcc/testsuite/g++.dg/concepts/equiv2.C
@@ -1,5 +1,5 @@
 // { dg-do run }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 
 // template<typename T>
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-inst1.C b/gcc/testsuite/g++.dg/concepts/explicit-inst1.C
index 3079ca50f647..89eeb156b574 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-inst1.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-inst1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-inst2.C b/gcc/testsuite/g++.dg/concepts/explicit-inst2.C
index 5e75f4ff6313..0319756bfc5c 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-inst2.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-inst2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-inst3.C b/gcc/testsuite/g++.dg/concepts/explicit-inst3.C
index a471657a750e..177fc6c1368c 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-inst3.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-inst3.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-inst4.C b/gcc/testsuite/g++.dg/concepts/explicit-inst4.C
index b075c1009e8e..cf0d8988bd30 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-inst4.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-inst4.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-spec1.C b/gcc/testsuite/g++.dg/concepts/explicit-spec1.C
index 6316410b950b..c6f559cd1af7 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-spec1.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-spec1.C
@@ -1,5 +1,5 @@
 // { dg-do run }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <cassert>
 
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-spec2.C b/gcc/testsuite/g++.dg/concepts/explicit-spec2.C
index 4f196243717b..8fa7e8aef166 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-spec2.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-spec2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-spec3.C b/gcc/testsuite/g++.dg/concepts/explicit-spec3.C
index 29546b3b37c4..6294cef5845e 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-spec3.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-spec3.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-spec4.C b/gcc/testsuite/g++.dg/concepts/explicit-spec4.C
index e9aacd51bbba..16698cbb366a 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-spec4.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-spec4.C
@@ -1,5 +1,5 @@
 // { dg-do run }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <cassert>
 
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-spec5.C b/gcc/testsuite/g++.dg/concepts/explicit-spec5.C
index 8047278aa77e..e889c2192bfd 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-spec5.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-spec5.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <cassert>
 
diff --git a/gcc/testsuite/g++.dg/concepts/explicit-spec6.C b/gcc/testsuite/g++.dg/concepts/explicit-spec6.C
index 3eba9ff7bfd0..0bf7640df27c 100644
--- a/gcc/testsuite/g++.dg/concepts/explicit-spec6.C
+++ b/gcc/testsuite/g++.dg/concepts/explicit-spec6.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 struct A {
diff --git a/gcc/testsuite/g++.dg/concepts/expression.C b/gcc/testsuite/g++.dg/concepts/expression.C
index 5ae04e43a12e..de68ef89ee6f 100644
--- a/gcc/testsuite/g++.dg/concepts/expression.C
+++ b/gcc/testsuite/g++.dg/concepts/expression.C
@@ -1,5 +1,5 @@
 // { dg-do run }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <cassert>
 #include <iostream>
diff --git a/gcc/testsuite/g++.dg/concepts/expression2.C b/gcc/testsuite/g++.dg/concepts/expression2.C
index 40c2034764a9..ebdadc231f38 100644
--- a/gcc/testsuite/g++.dg/concepts/expression2.C
+++ b/gcc/testsuite/g++.dg/concepts/expression2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 concept bool C1()
diff --git a/gcc/testsuite/g++.dg/concepts/expression3.C b/gcc/testsuite/g++.dg/concepts/expression3.C
index eb8406f13b01..77b414e5cfc3 100644
--- a/gcc/testsuite/g++.dg/concepts/expression3.C
+++ b/gcc/testsuite/g++.dg/concepts/expression3.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 concept bool C()
diff --git a/gcc/testsuite/g++.dg/concepts/feature-macro.C b/gcc/testsuite/g++.dg/concepts/feature-macro.C
index 7bc787559ec8..d8ea36981474 100644
--- a/gcc/testsuite/g++.dg/concepts/feature-macro.C
+++ b/gcc/testsuite/g++.dg/concepts/feature-macro.C
@@ -1,4 +1,4 @@
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #ifndef __cpp_concepts
 #error __cpp_concepts not defined
diff --git a/gcc/testsuite/g++.dg/concepts/fn-concept1.C b/gcc/testsuite/g++.dg/concepts/fn-concept1.C
index 385dcbc13cf1..4a8437f010b3 100644
--- a/gcc/testsuite/g++.dg/concepts/fn-concept1.C
+++ b/gcc/testsuite/g++.dg/concepts/fn-concept1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Tuple() { // { dg-error "multiple statements" }
diff --git a/gcc/testsuite/g++.dg/concepts/fn-concept2.C b/gcc/testsuite/g++.dg/concepts/fn-concept2.C
index 092c91c5b84c..86ba936d842b 100644
--- a/gcc/testsuite/g++.dg/concepts/fn-concept2.C
+++ b/gcc/testsuite/g++.dg/concepts/fn-concept2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept auto C1() { return 0; } // { dg-error "deduced return type" }
diff --git a/gcc/testsuite/g++.dg/concepts/fn1.C b/gcc/testsuite/g++.dg/concepts/fn1.C
index b2bdaf918852..c4f9f555e0a9 100644
--- a/gcc/testsuite/g++.dg/concepts/fn1.C
+++ b/gcc/testsuite/g++.dg/concepts/fn1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/fn10.C b/gcc/testsuite/g++.dg/concepts/fn10.C
index f4cd4c5ce346..859c1d5eb218 100644
--- a/gcc/testsuite/g++.dg/concepts/fn10.C
+++ b/gcc/testsuite/g++.dg/concepts/fn10.C
@@ -1,5 +1,5 @@
 // { dg-do compile }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Test that constraint satisfaction checks work even when
 // processing template declarations.
diff --git a/gcc/testsuite/g++.dg/concepts/fn2.C b/gcc/testsuite/g++.dg/concepts/fn2.C
index 0aee852ce38f..51a3fb5fd8e0 100644
--- a/gcc/testsuite/g++.dg/concepts/fn2.C
+++ b/gcc/testsuite/g++.dg/concepts/fn2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/fn3.C b/gcc/testsuite/g++.dg/concepts/fn3.C
index 06402e02c3bb..ef704f7e135d 100644
--- a/gcc/testsuite/g++.dg/concepts/fn3.C
+++ b/gcc/testsuite/g++.dg/concepts/fn3.C
@@ -1,5 +1,5 @@
 // { dg-do run }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <cassert>
 
diff --git a/gcc/testsuite/g++.dg/concepts/fn4.C b/gcc/testsuite/g++.dg/concepts/fn4.C
index 5ced6a7f390d..9fa5790fd5e9 100644
--- a/gcc/testsuite/g++.dg/concepts/fn4.C
+++ b/gcc/testsuite/g++.dg/concepts/fn4.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/fn5.C b/gcc/testsuite/g++.dg/concepts/fn5.C
index b3c3f70a8789..dd9a19e9f195 100644
--- a/gcc/testsuite/g++.dg/concepts/fn5.C
+++ b/gcc/testsuite/g++.dg/concepts/fn5.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Check shorthand notation.
 
diff --git a/gcc/testsuite/g++.dg/concepts/fn6.C b/gcc/testsuite/g++.dg/concepts/fn6.C
index 73ef19a20a77..f6f165e09995 100644
--- a/gcc/testsuite/g++.dg/concepts/fn6.C
+++ b/gcc/testsuite/g++.dg/concepts/fn6.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Redefinition errors.
 
diff --git a/gcc/testsuite/g++.dg/concepts/fn7.C b/gcc/testsuite/g++.dg/concepts/fn7.C
index 2abd34a1e780..dd16a9ae65b5 100644
--- a/gcc/testsuite/g++.dg/concepts/fn7.C
+++ b/gcc/testsuite/g++.dg/concepts/fn7.C
@@ -1,5 +1,5 @@
 // { dg-do link }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // FIXME: What is this actually testing?
 
diff --git a/gcc/testsuite/g++.dg/concepts/fn8.C b/gcc/testsuite/g++.dg/concepts/fn8.C
index 71141f6ff557..e7481be2f05c 100644
--- a/gcc/testsuite/g++.dg/concepts/fn8.C
+++ b/gcc/testsuite/g++.dg/concepts/fn8.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Class() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/fn9.C b/gcc/testsuite/g++.dg/concepts/fn9.C
index b7ac4e10a8da..c135bd7010a6 100644
--- a/gcc/testsuite/g++.dg/concepts/fn9.C
+++ b/gcc/testsuite/g++.dg/concepts/fn9.C
@@ -1,5 +1,5 @@
 // { dg-do run }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <cassert>
 
diff --git a/gcc/testsuite/g++.dg/concepts/friend1.C b/gcc/testsuite/g++.dg/concepts/friend1.C
index 286e7697c739..5c418cbf76cf 100644
--- a/gcc/testsuite/g++.dg/concepts/friend1.C
+++ b/gcc/testsuite/g++.dg/concepts/friend1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Eq() { return requires(T t) { t == t; }; }
diff --git a/gcc/testsuite/g++.dg/concepts/friend2.C b/gcc/testsuite/g++.dg/concepts/friend2.C
index 38b230c4ff7a..6268801a260c 100644
--- a/gcc/testsuite/g++.dg/concepts/friend2.C
+++ b/gcc/testsuite/g++.dg/concepts/friend2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Eq() { return requires(T t) { t == t; }; }
diff --git a/gcc/testsuite/g++.dg/concepts/generic-fn-err.C b/gcc/testsuite/g++.dg/concepts/generic-fn-err.C
index 1e975108257b..03a47d5c9597 100644
--- a/gcc/testsuite/g++.dg/concepts/generic-fn-err.C
+++ b/gcc/testsuite/g++.dg/concepts/generic-fn-err.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/generic-fn.C b/gcc/testsuite/g++.dg/concepts/generic-fn.C
index 778356db1803..d74ea21b6eff 100644
--- a/gcc/testsuite/g++.dg/concepts/generic-fn.C
+++ b/gcc/testsuite/g++.dg/concepts/generic-fn.C
@@ -1,5 +1,5 @@
 // { dg-do run }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <cassert>
 #include <type_traits>
diff --git a/gcc/testsuite/g++.dg/concepts/iconv1.C b/gcc/testsuite/g++.dg/concepts/iconv1.C
index c4dd38fe5b45..28f3566d4178 100644
--- a/gcc/testsuite/g++.dg/concepts/iconv1.C
+++ b/gcc/testsuite/g++.dg/concepts/iconv1.C
@@ -1,5 +1,5 @@
 // PR c++/67240
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 int foo(int x)
 {
diff --git a/gcc/testsuite/g++.dg/concepts/inherit-ctor1.C b/gcc/testsuite/g++.dg/concepts/inherit-ctor1.C
index 29433ade7b4f..6f5115c6c85f 100644
--- a/gcc/testsuite/g++.dg/concepts/inherit-ctor1.C
+++ b/gcc/testsuite/g++.dg/concepts/inherit-ctor1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/inherit-ctor2.C b/gcc/testsuite/g++.dg/concepts/inherit-ctor2.C
index 4f39203db4c3..435745a1fa9e 100644
--- a/gcc/testsuite/g++.dg/concepts/inherit-ctor2.C
+++ b/gcc/testsuite/g++.dg/concepts/inherit-ctor2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/inherit-ctor3.C b/gcc/testsuite/g++.dg/concepts/inherit-ctor3.C
index 3d0ddf210d12..07499bb40f9d 100644
--- a/gcc/testsuite/g++.dg/concepts/inherit-ctor3.C
+++ b/gcc/testsuite/g++.dg/concepts/inherit-ctor3.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/inherit-ctor4.C b/gcc/testsuite/g++.dg/concepts/inherit-ctor4.C
index cd9565f660f0..4c53205466dd 100644
--- a/gcc/testsuite/g++.dg/concepts/inherit-ctor4.C
+++ b/gcc/testsuite/g++.dg/concepts/inherit-ctor4.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/intro1.C b/gcc/testsuite/g++.dg/concepts/intro1.C
index 1b5f5d14b7e5..5f036c4b6454 100644
--- a/gcc/testsuite/g++.dg/concepts/intro1.C
+++ b/gcc/testsuite/g++.dg/concepts/intro1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C = __is_class(T);
diff --git a/gcc/testsuite/g++.dg/concepts/intro2.C b/gcc/testsuite/g++.dg/concepts/intro2.C
index 91a1cacf9c0e..1db1d7a493fb 100644
--- a/gcc/testsuite/g++.dg/concepts/intro2.C
+++ b/gcc/testsuite/g++.dg/concepts/intro2.C
@@ -1,5 +1,5 @@
 // { dg-do run }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <cassert>
 
diff --git a/gcc/testsuite/g++.dg/concepts/intro3.C b/gcc/testsuite/g++.dg/concepts/intro3.C
index 5dd95c698e12..3cb3ecbb8b4b 100644
--- a/gcc/testsuite/g++.dg/concepts/intro3.C
+++ b/gcc/testsuite/g++.dg/concepts/intro3.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename ... T>
   concept bool C1 = true;
diff --git a/gcc/testsuite/g++.dg/concepts/intro4.C b/gcc/testsuite/g++.dg/concepts/intro4.C
index 6d8aec3ff616..182129165556 100644
--- a/gcc/testsuite/g++.dg/concepts/intro4.C
+++ b/gcc/testsuite/g++.dg/concepts/intro4.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename ... T>
   concept bool C1 = true;
diff --git a/gcc/testsuite/g++.dg/concepts/intro5.C b/gcc/testsuite/g++.dg/concepts/intro5.C
index 64771cd6e251..31924f930a70 100644
--- a/gcc/testsuite/g++.dg/concepts/intro5.C
+++ b/gcc/testsuite/g++.dg/concepts/intro5.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T, typename U = int>
   concept bool C()
diff --git a/gcc/testsuite/g++.dg/concepts/intro6.C b/gcc/testsuite/g++.dg/concepts/intro6.C
index 4e168ef3c7dc..f8ed6669f14f 100644
--- a/gcc/testsuite/g++.dg/concepts/intro6.C
+++ b/gcc/testsuite/g++.dg/concepts/intro6.C
@@ -1,5 +1,5 @@
 // PR c++/67003
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 namespace X {
   template<class>
diff --git a/gcc/testsuite/g++.dg/concepts/intro7.C b/gcc/testsuite/g++.dg/concepts/intro7.C
index d92eafcfbd57..914c5fd61100 100644
--- a/gcc/testsuite/g++.dg/concepts/intro7.C
+++ b/gcc/testsuite/g++.dg/concepts/intro7.C
@@ -1,5 +1,5 @@
 // PR c++/66985
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <template <class> class T>
 concept bool _Valid = requires { typename T<int>; };
diff --git a/gcc/testsuite/g++.dg/concepts/member-concept.C b/gcc/testsuite/g++.dg/concepts/member-concept.C
index 46404e3ad4f0..2b0604648313 100644
--- a/gcc/testsuite/g++.dg/concepts/member-concept.C
+++ b/gcc/testsuite/g++.dg/concepts/member-concept.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 struct Base {
   template<typename T>
diff --git a/gcc/testsuite/g++.dg/concepts/memfun-err.C b/gcc/testsuite/g++.dg/concepts/memfun-err.C
index a62fe5ef2203..e44273ca8c87 100644
--- a/gcc/testsuite/g++.dg/concepts/memfun-err.C
+++ b/gcc/testsuite/g++.dg/concepts/memfun-err.C
@@ -1,5 +1,5 @@
 // { dg-do run}
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 
 template<typename T>
diff --git a/gcc/testsuite/g++.dg/concepts/memfun.C b/gcc/testsuite/g++.dg/concepts/memfun.C
index a96c01816534..523410cab984 100644
--- a/gcc/testsuite/g++.dg/concepts/memfun.C
+++ b/gcc/testsuite/g++.dg/concepts/memfun.C
@@ -1,5 +1,5 @@
 // { dg-do run}
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <cassert>
 
diff --git a/gcc/testsuite/g++.dg/concepts/partial-concept-id1.C b/gcc/testsuite/g++.dg/concepts/partial-concept-id1.C
index 114c12f85bc5..117400cf1b21 100644
--- a/gcc/testsuite/g++.dg/concepts/partial-concept-id1.C
+++ b/gcc/testsuite/g++.dg/concepts/partial-concept-id1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Type() { return true; }
diff --git a/gcc/testsuite/g++.dg/concepts/partial-concept-id2.C b/gcc/testsuite/g++.dg/concepts/partial-concept-id2.C
index fb754483db44..2e6866ecb9f1 100644
--- a/gcc/testsuite/g++.dg/concepts/partial-concept-id2.C
+++ b/gcc/testsuite/g++.dg/concepts/partial-concept-id2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Make sure that we check partial concept ids
 // with variable concepts.
diff --git a/gcc/testsuite/g++.dg/concepts/partial-spec.C b/gcc/testsuite/g++.dg/concepts/partial-spec.C
index fe612d4ada0e..5db9a585090d 100644
--- a/gcc/testsuite/g++.dg/concepts/partial-spec.C
+++ b/gcc/testsuite/g++.dg/concepts/partial-spec.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Check that constraints don't break unconstrained partial
 // specializations.
diff --git a/gcc/testsuite/g++.dg/concepts/partial-spec2.C b/gcc/testsuite/g++.dg/concepts/partial-spec2.C
index db7545586a9a..bc7621bec4d4 100644
--- a/gcc/testsuite/g++.dg/concepts/partial-spec2.C
+++ b/gcc/testsuite/g++.dg/concepts/partial-spec2.C
@@ -1,5 +1,5 @@
 // PR c++/67084
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T>
 constexpr bool p = false;
diff --git a/gcc/testsuite/g++.dg/concepts/partial-spec3.C b/gcc/testsuite/g++.dg/concepts/partial-spec3.C
index d73d7879a304..9387ce00a1b7 100644
--- a/gcc/testsuite/g++.dg/concepts/partial-spec3.C
+++ b/gcc/testsuite/g++.dg/concepts/partial-spec3.C
@@ -1,4 +1,4 @@
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T> struct A { };
 template <class T> requires false struct A<T*> { };
diff --git a/gcc/testsuite/g++.dg/concepts/partial-spec4.C b/gcc/testsuite/g++.dg/concepts/partial-spec4.C
index d4b8e9c92f78..80e41ab83990 100644
--- a/gcc/testsuite/g++.dg/concepts/partial-spec4.C
+++ b/gcc/testsuite/g++.dg/concepts/partial-spec4.C
@@ -1,4 +1,4 @@
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T> concept bool is_int = __is_same_as(T,int);
 
diff --git a/gcc/testsuite/g++.dg/concepts/partial-spec5.C b/gcc/testsuite/g++.dg/concepts/partial-spec5.C
index dcf167bc4ae3..32a5eae693c1 100644
--- a/gcc/testsuite/g++.dg/concepts/partial-spec5.C
+++ b/gcc/testsuite/g++.dg/concepts/partial-spec5.C
@@ -1,5 +1,5 @@
 // PR c++/67138
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T>
 concept bool _Auto = true;
diff --git a/gcc/testsuite/g++.dg/concepts/partial-spec6.C b/gcc/testsuite/g++.dg/concepts/partial-spec6.C
index 2196fcdf3aa6..50ef28991030 100644
--- a/gcc/testsuite/g++.dg/concepts/partial-spec6.C
+++ b/gcc/testsuite/g++.dg/concepts/partial-spec6.C
@@ -1,5 +1,5 @@
 // PR c++/67152
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T>
 concept bool HasType = requires { typename T::type; };
diff --git a/gcc/testsuite/g++.dg/concepts/placeholder1.C b/gcc/testsuite/g++.dg/concepts/placeholder1.C
index 0b5a7cf27859..757bcef9b1ce 100644
--- a/gcc/testsuite/g++.dg/concepts/placeholder1.C
+++ b/gcc/testsuite/g++.dg/concepts/placeholder1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T, typename U>
 struct is_same
diff --git a/gcc/testsuite/g++.dg/concepts/placeholder2.C b/gcc/testsuite/g++.dg/concepts/placeholder2.C
index 8165c8134f9d..cf2013e63a6b 100644
--- a/gcc/testsuite/g++.dg/concepts/placeholder2.C
+++ b/gcc/testsuite/g++.dg/concepts/placeholder2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Check argument deduction constraints.
 // TODO: We shoul have more of these...
diff --git a/gcc/testsuite/g++.dg/concepts/placeholder3.C b/gcc/testsuite/g++.dg/concepts/placeholder3.C
index bd89551aa5bc..208fc29a0d3f 100644
--- a/gcc/testsuite/g++.dg/concepts/placeholder3.C
+++ b/gcc/testsuite/g++.dg/concepts/placeholder3.C
@@ -1,5 +1,5 @@
 // PR c++/66218
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T, class U>
 concept bool Same = __is_same_as(T, U);
diff --git a/gcc/testsuite/g++.dg/concepts/placeholder4.C b/gcc/testsuite/g++.dg/concepts/placeholder4.C
index e34fc94e6cf6..2fb47580cdba 100644
--- a/gcc/testsuite/g++.dg/concepts/placeholder4.C
+++ b/gcc/testsuite/g++.dg/concepts/placeholder4.C
@@ -1,5 +1,5 @@
 // PR c++/66218
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T, class U>
 concept bool Same = __is_same_as(T, U);
diff --git a/gcc/testsuite/g++.dg/concepts/placeholder5.C b/gcc/testsuite/g++.dg/concepts/placeholder5.C
index 6aaf57b32879..e1d3092a77db 100644
--- a/gcc/testsuite/g++.dg/concepts/placeholder5.C
+++ b/gcc/testsuite/g++.dg/concepts/placeholder5.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T, class U>
 concept bool Same = __is_same_as(T, U);
diff --git a/gcc/testsuite/g++.dg/concepts/placeholder6.C b/gcc/testsuite/g++.dg/concepts/placeholder6.C
index 7f2e67a9192b..ee218fdf9042 100644
--- a/gcc/testsuite/g++.dg/concepts/placeholder6.C
+++ b/gcc/testsuite/g++.dg/concepts/placeholder6.C
@@ -1,4 +1,4 @@
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <int I> struct B { static const int i = I; };
 template <int I> concept bool Few = I < 10;
diff --git a/gcc/testsuite/g++.dg/concepts/pr65552.C b/gcc/testsuite/g++.dg/concepts/pr65552.C
index c72e6c638f57..c1cc0b165b0d 100644
--- a/gcc/testsuite/g++.dg/concepts/pr65552.C
+++ b/gcc/testsuite/g++.dg/concepts/pr65552.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 concept bool Concept() {
diff --git a/gcc/testsuite/g++.dg/concepts/pr65575.C b/gcc/testsuite/g++.dg/concepts/pr65575.C
index fa24b7be0e07..18e805959de5 100644
--- a/gcc/testsuite/g++.dg/concepts/pr65575.C
+++ b/gcc/testsuite/g++.dg/concepts/pr65575.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 concept bool C = false;
diff --git a/gcc/testsuite/g++.dg/concepts/pr65634.C b/gcc/testsuite/g++.dg/concepts/pr65634.C
index 31dc87aa6c3c..df64a3f386a5 100644
--- a/gcc/testsuite/g++.dg/concepts/pr65634.C
+++ b/gcc/testsuite/g++.dg/concepts/pr65634.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 concept bool C1() {
diff --git a/gcc/testsuite/g++.dg/concepts/pr65636.C b/gcc/testsuite/g++.dg/concepts/pr65636.C
index 8b6f2a1ad6eb..ddeef8203146 100644
--- a/gcc/testsuite/g++.dg/concepts/pr65636.C
+++ b/gcc/testsuite/g++.dg/concepts/pr65636.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 using TD = int;
 
diff --git a/gcc/testsuite/g++.dg/concepts/pr65681.C b/gcc/testsuite/g++.dg/concepts/pr65681.C
index bdbbd66e7474..fcbbab376ac6 100644
--- a/gcc/testsuite/g++.dg/concepts/pr65681.C
+++ b/gcc/testsuite/g++.dg/concepts/pr65681.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 concept bool C()
diff --git a/gcc/testsuite/g++.dg/concepts/pr65848.C b/gcc/testsuite/g++.dg/concepts/pr65848.C
index d0bb6a2afb85..4affa2366d2f 100644
--- a/gcc/testsuite/g++.dg/concepts/pr65848.C
+++ b/gcc/testsuite/g++.dg/concepts/pr65848.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Performance test... This should be fast.
 
diff --git a/gcc/testsuite/g++.dg/concepts/pr65854.C b/gcc/testsuite/g++.dg/concepts/pr65854.C
index 4b0befa55997..c615ed7b4da4 100644
--- a/gcc/testsuite/g++.dg/concepts/pr65854.C
+++ b/gcc/testsuite/g++.dg/concepts/pr65854.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Handle alias templates in type requirements.
 
diff --git a/gcc/testsuite/g++.dg/concepts/pr66091.C b/gcc/testsuite/g++.dg/concepts/pr66091.C
index ee9d1150fdbf..b53f64c7bd3a 100644
--- a/gcc/testsuite/g++.dg/concepts/pr66091.C
+++ b/gcc/testsuite/g++.dg/concepts/pr66091.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 concept bool C1()
diff --git a/gcc/testsuite/g++.dg/concepts/pr67249.C b/gcc/testsuite/g++.dg/concepts/pr67249.C
index cb0445d2a360..9cfada59b3ee 100644
--- a/gcc/testsuite/g++.dg/concepts/pr67249.C
+++ b/gcc/testsuite/g++.dg/concepts/pr67249.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<class T> concept bool C1 = true;
 template<class A, class B> struct Pair {};
diff --git a/gcc/testsuite/g++.dg/concepts/pr68434.C b/gcc/testsuite/g++.dg/concepts/pr68434.C
index d5f901ac3c64..ece5bb7c0019 100644
--- a/gcc/testsuite/g++.dg/concepts/pr68434.C
+++ b/gcc/testsuite/g++.dg/concepts/pr68434.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class>
 concept bool C1 () {
diff --git a/gcc/testsuite/g++.dg/concepts/pr68683.C b/gcc/testsuite/g++.dg/concepts/pr68683.C
index a0d8fcf46b01..eef1b33c96a6 100644
--- a/gcc/testsuite/g++.dg/concepts/pr68683.C
+++ b/gcc/testsuite/g++.dg/concepts/pr68683.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <typename, typename>
 struct is_same {
diff --git a/gcc/testsuite/g++.dg/concepts/req-neg1.C b/gcc/testsuite/g++.dg/concepts/req-neg1.C
index 0b7520e185c4..6c80d81a3026 100644
--- a/gcc/testsuite/g++.dg/concepts/req-neg1.C
+++ b/gcc/testsuite/g++.dg/concepts/req-neg1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 void f1(int a) requires true;         // OK
 auto f2(int a) -> bool requires true; // OK
diff --git a/gcc/testsuite/g++.dg/concepts/req1.C b/gcc/testsuite/g++.dg/concepts/req1.C
index 02d5de09ec9a..0636f1dfdb82 100644
--- a/gcc/testsuite/g++.dg/concepts/req1.C
+++ b/gcc/testsuite/g++.dg/concepts/req1.C
@@ -1,5 +1,5 @@
 // { dg-do compile }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Class () { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/req10.C b/gcc/testsuite/g++.dg/concepts/req10.C
index bd3b4e3e2f5f..0352a08113b1 100644
--- a/gcc/testsuite/g++.dg/concepts/req10.C
+++ b/gcc/testsuite/g++.dg/concepts/req10.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Test that standard conversions are checked with
 // implicit conversion constraints.
diff --git a/gcc/testsuite/g++.dg/concepts/req11.C b/gcc/testsuite/g++.dg/concepts/req11.C
index 3e21c11113fd..1a259e82990e 100644
--- a/gcc/testsuite/g++.dg/concepts/req11.C
+++ b/gcc/testsuite/g++.dg/concepts/req11.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Check that we can evaluate constant requires-expressions
 // as constant expressions, for the curious case when they
diff --git a/gcc/testsuite/g++.dg/concepts/req12.C b/gcc/testsuite/g++.dg/concepts/req12.C
index 7b23d113cb29..f28551443c36 100644
--- a/gcc/testsuite/g++.dg/concepts/req12.C
+++ b/gcc/testsuite/g++.dg/concepts/req12.C
@@ -1,5 +1,5 @@
 // PR c++/66218
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <type_traits>
 
diff --git a/gcc/testsuite/g++.dg/concepts/req13.C b/gcc/testsuite/g++.dg/concepts/req13.C
index 54fcd8b0678c..559c12874093 100644
--- a/gcc/testsuite/g++.dg/concepts/req13.C
+++ b/gcc/testsuite/g++.dg/concepts/req13.C
@@ -1,5 +1,5 @@
 // PR c++/66758
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T, class...Args>
 concept bool Constructible =
diff --git a/gcc/testsuite/g++.dg/concepts/req14.C b/gcc/testsuite/g++.dg/concepts/req14.C
index e86281a39313..de7efcd2c738 100644
--- a/gcc/testsuite/g++.dg/concepts/req14.C
+++ b/gcc/testsuite/g++.dg/concepts/req14.C
@@ -1,5 +1,5 @@
 // PR c++/66758
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T, class U>
 concept bool C = requires (T t, U u) { t + u; };
diff --git a/gcc/testsuite/g++.dg/concepts/req15.C b/gcc/testsuite/g++.dg/concepts/req15.C
index 09ebf89ef1be..537669bbcb43 100644
--- a/gcc/testsuite/g++.dg/concepts/req15.C
+++ b/gcc/testsuite/g++.dg/concepts/req15.C
@@ -1,5 +1,5 @@
 // PR c++/66832
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T, class U, unsigned N>
   requires requires (T& t, U &u) { t.foo(); u.foo(); }
diff --git a/gcc/testsuite/g++.dg/concepts/req16.C b/gcc/testsuite/g++.dg/concepts/req16.C
index 67ae5b5126cc..2704c38bacb4 100644
--- a/gcc/testsuite/g++.dg/concepts/req16.C
+++ b/gcc/testsuite/g++.dg/concepts/req16.C
@@ -1,5 +1,5 @@
 // PR c++/66988
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <type_traits>
 
diff --git a/gcc/testsuite/g++.dg/concepts/req17.C b/gcc/testsuite/g++.dg/concepts/req17.C
index 48bd0a8c2cd6..af622e2fb6d4 100644
--- a/gcc/testsuite/g++.dg/concepts/req17.C
+++ b/gcc/testsuite/g++.dg/concepts/req17.C
@@ -1,5 +1,5 @@
 // PR c++/67018
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <typename T>
 constexpr bool Val = true;
diff --git a/gcc/testsuite/g++.dg/concepts/req18.C b/gcc/testsuite/g++.dg/concepts/req18.C
index 9a474376137e..0b6848b42f25 100644
--- a/gcc/testsuite/g++.dg/concepts/req18.C
+++ b/gcc/testsuite/g++.dg/concepts/req18.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class> struct all_same {
   static constexpr bool value = 1;
diff --git a/gcc/testsuite/g++.dg/concepts/req2.C b/gcc/testsuite/g++.dg/concepts/req2.C
index a28f30b5b18d..b1258c4508b5 100644
--- a/gcc/testsuite/g++.dg/concepts/req2.C
+++ b/gcc/testsuite/g++.dg/concepts/req2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Class () { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/req3.C b/gcc/testsuite/g++.dg/concepts/req3.C
index 69581ee43eac..5bc7ac790a34 100644
--- a/gcc/testsuite/g++.dg/concepts/req3.C
+++ b/gcc/testsuite/g++.dg/concepts/req3.C
@@ -1,5 +1,5 @@
 // { dg-do run }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Class () { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/req4.C b/gcc/testsuite/g++.dg/concepts/req4.C
index 20778342e52b..e7e71a47bd29 100644
--- a/gcc/testsuite/g++.dg/concepts/req4.C
+++ b/gcc/testsuite/g++.dg/concepts/req4.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 struct fool {
   constexpr fool operator&&(fool) const { return {}; }
diff --git a/gcc/testsuite/g++.dg/concepts/req5.C b/gcc/testsuite/g++.dg/concepts/req5.C
index c0af1f884954..17db0dd6abcf 100644
--- a/gcc/testsuite/g++.dg/concepts/req5.C
+++ b/gcc/testsuite/g++.dg/concepts/req5.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 struct fool { };
 
diff --git a/gcc/testsuite/g++.dg/concepts/req6.C b/gcc/testsuite/g++.dg/concepts/req6.C
index e4f20ecb67ca..e8e94c02ff26 100644
--- a/gcc/testsuite/g++.dg/concepts/req6.C
+++ b/gcc/testsuite/g++.dg/concepts/req6.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 struct X { };
 int operator==(X, X) { return 0; }
diff --git a/gcc/testsuite/g++.dg/concepts/req7.C b/gcc/testsuite/g++.dg/concepts/req7.C
index 51aba7b2e6f5..ef25987a4f8a 100644
--- a/gcc/testsuite/g++.dg/concepts/req7.C
+++ b/gcc/testsuite/g++.dg/concepts/req7.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <vector>
 
diff --git a/gcc/testsuite/g++.dg/concepts/req8.C b/gcc/testsuite/g++.dg/concepts/req8.C
index 35c08541b60c..4adbc78978c0 100644
--- a/gcc/testsuite/g++.dg/concepts/req8.C
+++ b/gcc/testsuite/g++.dg/concepts/req8.C
@@ -1,5 +1,5 @@
 // { dg-do compile }
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 // Check that type requirements are normalized correctly.
 
diff --git a/gcc/testsuite/g++.dg/concepts/req9.C b/gcc/testsuite/g++.dg/concepts/req9.C
index 5654be0a0fe4..5f66376fd0b3 100644
--- a/gcc/testsuite/g++.dg/concepts/req9.C
+++ b/gcc/testsuite/g++.dg/concepts/req9.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 struct S1 {};
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm1.C b/gcc/testsuite/g++.dg/concepts/template-parm1.C
index 20a7fb6b1c35..101432feefba 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm1.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C1 = __is_same_as(T, int);
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm10.C b/gcc/testsuite/g++.dg/concepts/template-parm10.C
index b80328995b0d..b61912c84bcd 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm10.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm10.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<int N, class T>
   concept bool P() { return true; }
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm11.C b/gcc/testsuite/g++.dg/concepts/template-parm11.C
index 95ce78451167..1f0d91ad778b 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm11.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm11.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 concept bool NameProvider()
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm12.C b/gcc/testsuite/g++.dg/concepts/template-parm12.C
index 1639f26dbf10..edeeb909fcb2 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm12.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm12.C
@@ -1,5 +1,5 @@
 // Conceptized version of template/ttp23.C
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T> concept bool Foo = true;
 
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm2.C b/gcc/testsuite/g++.dg/concepts/template-parm2.C
index ad715e11a324..146d1c6def15 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm2.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C1 = __is_same_as(T, int);
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm3.C b/gcc/testsuite/g++.dg/concepts/template-parm3.C
index e412fb4ca125..5fcd5a29a342 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm3.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm3.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C1 = __is_same_as(T, int);
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm4.C b/gcc/testsuite/g++.dg/concepts/template-parm4.C
index a29bb11a6799..ac9d2af7cb8b 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm4.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm4.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C1 = __is_same_as(T, int);
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm5.C b/gcc/testsuite/g++.dg/concepts/template-parm5.C
index f33742becd25..25bd916ca017 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm5.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm5.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C1 = __is_same_as(T, int);
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm6.C b/gcc/testsuite/g++.dg/concepts/template-parm6.C
index d23f2594b465..e70cdc0b2b0a 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm6.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm6.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename... Ts> struct are_same;
 
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm7.C b/gcc/testsuite/g++.dg/concepts/template-parm7.C
index 10869840fdde..3e2a2f23377c 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm7.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm7.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename... Ts> struct are_same;
 
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm8.C b/gcc/testsuite/g++.dg/concepts/template-parm8.C
index f604d5a6a2b0..69a31bcb8e6a 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm8.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm8.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/template-parm9.C b/gcc/testsuite/g++.dg/concepts/template-parm9.C
index 7e6898405ae5..06b0f96e094e 100644
--- a/gcc/testsuite/g++.dg/concepts/template-parm9.C
+++ b/gcc/testsuite/g++.dg/concepts/template-parm9.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C() { return __is_class(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/template-template-parm1.C b/gcc/testsuite/g++.dg/concepts/template-template-parm1.C
index 40912843714b..c2dcc3a8c1b4 100644
--- a/gcc/testsuite/g++.dg/concepts/template-template-parm1.C
+++ b/gcc/testsuite/g++.dg/concepts/template-template-parm1.C
@@ -1,5 +1,5 @@
 // PR c++/66937
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 #include <tuple>
 
diff --git a/gcc/testsuite/g++.dg/concepts/traits1.C b/gcc/testsuite/g++.dg/concepts/traits1.C
index f07c87874729..7ccf087aaed8 100644
--- a/gcc/testsuite/g++.dg/concepts/traits1.C
+++ b/gcc/testsuite/g++.dg/concepts/traits1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Nothrow_assignable() { return __has_nothrow_assign(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/traits2.C b/gcc/testsuite/g++.dg/concepts/traits2.C
index 28ced34c63e3..971a67bf64f9 100644
--- a/gcc/testsuite/g++.dg/concepts/traits2.C
+++ b/gcc/testsuite/g++.dg/concepts/traits2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool Nothrow_assignable() { return __has_nothrow_assign(T); }
diff --git a/gcc/testsuite/g++.dg/concepts/var-concept1.C b/gcc/testsuite/g++.dg/concepts/var-concept1.C
index eb8a2b797a39..b99016f9a8bf 100644
--- a/gcc/testsuite/g++.dg/concepts/var-concept1.C
+++ b/gcc/testsuite/g++.dg/concepts/var-concept1.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
 concept bool C1 = __is_class(T);
diff --git a/gcc/testsuite/g++.dg/concepts/var-concept2.C b/gcc/testsuite/g++.dg/concepts/var-concept2.C
index 71663bdec5fb..21c69dd4a430 100644
--- a/gcc/testsuite/g++.dg/concepts/var-concept2.C
+++ b/gcc/testsuite/g++.dg/concepts/var-concept2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C1 = __is_class(T);
diff --git a/gcc/testsuite/g++.dg/concepts/var-concept3.C b/gcc/testsuite/g++.dg/concepts/var-concept3.C
index c90102848d4e..d27e4fa24b72 100644
--- a/gcc/testsuite/g++.dg/concepts/var-concept3.C
+++ b/gcc/testsuite/g++.dg/concepts/var-concept3.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T>
   concept bool C1 = __is_class(T);
diff --git a/gcc/testsuite/g++.dg/concepts/var-concept4.C b/gcc/testsuite/g++.dg/concepts/var-concept4.C
index b39835396165..1870a42dcb0e 100644
--- a/gcc/testsuite/g++.dg/concepts/var-concept4.C
+++ b/gcc/testsuite/g++.dg/concepts/var-concept4.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T, typename U>
 concept bool Same = __is_same_as(T, U);
diff --git a/gcc/testsuite/g++.dg/concepts/var-concept5.C b/gcc/testsuite/g++.dg/concepts/var-concept5.C
index 13f86dd31247..ca163321e762 100644
--- a/gcc/testsuite/g++.dg/concepts/var-concept5.C
+++ b/gcc/testsuite/g++.dg/concepts/var-concept5.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template<typename T1, typename T2>
 concept bool C1 = true;
diff --git a/gcc/testsuite/g++.dg/concepts/var-concept6.C b/gcc/testsuite/g++.dg/concepts/var-concept6.C
index 2f775fd62e0f..40be4f9d02f6 100644
--- a/gcc/testsuite/g++.dg/concepts/var-concept6.C
+++ b/gcc/testsuite/g++.dg/concepts/var-concept6.C
@@ -1,4 +1,4 @@
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T>
 concept int C = true;		// { dg-error "bool" }
diff --git a/gcc/testsuite/g++.dg/concepts/var-templ1.C b/gcc/testsuite/g++.dg/concepts/var-templ1.C
index 79476c354166..7dfa2400d3cf 100644
--- a/gcc/testsuite/g++.dg/concepts/var-templ1.C
+++ b/gcc/testsuite/g++.dg/concepts/var-templ1.C
@@ -1,5 +1,5 @@
 // PR c++/67117
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T>
   requires false
diff --git a/gcc/testsuite/g++.dg/concepts/var-templ2.C b/gcc/testsuite/g++.dg/concepts/var-templ2.C
index e615f21457dd..dc0be75cae73 100644
--- a/gcc/testsuite/g++.dg/concepts/var-templ2.C
+++ b/gcc/testsuite/g++.dg/concepts/var-templ2.C
@@ -1,5 +1,5 @@
 // PR c++/67139
-// { dg-options -std=c++1z }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T>
 constexpr typename T::type::value_type _v = T::type::value;
diff --git a/gcc/testsuite/g++.dg/concepts/variadic1.C b/gcc/testsuite/g++.dg/concepts/variadic1.C
index ed3d4f1e01d7..8129463ae785 100644
--- a/gcc/testsuite/g++.dg/concepts/variadic1.C
+++ b/gcc/testsuite/g++.dg/concepts/variadic1.C
@@ -1,5 +1,5 @@
 // PR c++/66712
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T, class...Args>
 concept bool _Constructible_ =
diff --git a/gcc/testsuite/g++.dg/concepts/variadic2.C b/gcc/testsuite/g++.dg/concepts/variadic2.C
index 6c552771d59c..f7aa7108480f 100644
--- a/gcc/testsuite/g++.dg/concepts/variadic2.C
+++ b/gcc/testsuite/g++.dg/concepts/variadic2.C
@@ -1,4 +1,4 @@
-// { dg-options "-std=c++1z" }
+// { dg-options "-std=c++1z -fconcepts" }
 
 template <class T> concept bool Copyable = requires (T t) { T(t); };
 template <class T> concept bool Constructable = requires { T(); };
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto3.C b/gcc/testsuite/g++.dg/cpp0x/auto3.C
index 27aab5738c82..ed7084b771e3 100644
--- a/gcc/testsuite/g++.dg/cpp0x/auto3.C
+++ b/gcc/testsuite/g++.dg/cpp0x/auto3.C
@@ -17,11 +17,11 @@ struct A { };
 
 A<int> A1;
 // CWG issue 625
-A<auto> A2 = A1;		// { dg-error "" "" { target { ! c++1z } } }
+A<auto> A2 = A1;		// { dg-error "" "" { target { ! concepts } } }
 
 auto foo() { }			// { dg-error "auto" "" { target { ! c++14 } } }
 
-void bar(auto i)		// { dg-error "incomplete|auto" "" { target { ! c++1z } } }
+void bar(auto i)		// { dg-error "incomplete|auto" "" { target { ! concepts } } }
 {
   (void)i;
 }
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto9.C b/gcc/testsuite/g++.dg/cpp0x/auto9.C
index ee204410368a..9001f78fa45e 100644
--- a/gcc/testsuite/g++.dg/cpp0x/auto9.C
+++ b/gcc/testsuite/g++.dg/cpp0x/auto9.C
@@ -116,8 +116,8 @@ template <auto V = 4> struct G {};		// { dg-error "auto" }
 template <typename T> struct H { H (); ~H (); };
 H<auto> h;					// { dg-error "invalid|initializer" }
 
-void qq (auto);		       // { dg-error "auto" "" { target { ! c++1z } } }
-void qr (auto*);	       // { dg-error "auto" "" { target { ! c++1z } } }
+void qq (auto);		       // { dg-error "auto" "" { target { ! concepts } } }
+void qr (auto*);	       // { dg-error "auto" "" { target { ! concepts } } }
 
 // PR c++/46145
 typedef auto autot;		// { dg-error "auto" }
diff --git a/gcc/testsuite/lib/g++-dg.exp b/gcc/testsuite/lib/g++-dg.exp
index 1343533584fc..4f7d18a18c06 100644
--- a/gcc/testsuite/lib/g++-dg.exp
+++ b/gcc/testsuite/lib/g++-dg.exp
@@ -56,6 +56,8 @@ proc g++-dg-runtest { testcases flags default-extra-flags } {
 	    }
 	    set option_list { }
 	    foreach x $std_list {
+		# Handle "concepts" as C++1z plus Concepts TS.
+		if { $x eq "concepts" } then { set x "1z -fconcepts" }
 		lappend option_list "${std_prefix}$x"
 	    }
 	} else {
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 16d358882d59..5af139b55ab9 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -6557,6 +6557,11 @@ proc check_effective_target_c++1z { } {
     return [check_effective_target_c++1z_only]
 }
 
+# Check for C++ Concepts TS support, i.e. -fconcepts flag.
+proc check_effective_target_concepts { } {
+    return [check-flags { "" { } { -fconcepts } }]
+}
+
 # Return 1 if expensive testcases should be run.
 
 proc check_effective_target_run_expensive_tests { } {