This adds a note suggesting to enable concepts whenever 'requires' is parsed as
an invalid type name with concepts disabled.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK to commit?
gcc/cp/ChangeLog:
* parser.c (cp_parser_diagnose_invalid_type_name): Suggest to enable
concepts if the invalid identifier is 'requires'.
gcc/testsuite/ChangeLog:
* g++.dg/concepts/diagnostic11.C: New test.
---
gcc/cp/parser.c | 3 +++
gcc/testsuite/g++.dg/concepts/diagnostic11.C | 6 ++++++
2 files changed, 9 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic11.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 47e3f2bbd3d..337f22d2784 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -3378,6 +3378,9 @@ cp_parser_diagnose_invalid_type_name (cp_parser *parser,
tree id,
else if (!flag_concepts && id == ridpointers[(int)RID_CONCEPT])
inform (location, "%<concept%> only available with %<-std=c++2a%> or "
"%<-fconcepts%>");
+ else if (!flag_concepts && id == ridpointers[(int)RID_REQUIRES])
+ inform (location, "%<requires%> only available with %<-std=c++2a%> or "
+ "%<-fconcepts%>");
else if (processing_template_decl && current_class_type
&& TYPE_BINFO (current_class_type))
{
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic11.C
b/gcc/testsuite/g++.dg/concepts/diagnostic11.C
new file mode 100644
index 00000000000..7c60912352a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic11.C
@@ -0,0 +1,6 @@
+// { dg-do compile { target c++17_only } }
+
+template <bool B>
+ requires B // { dg-error ".requires. does not name a type" }
+// { dg-message ".requires. only available with" "" { target *-*-* } .-1 }
+void foo() { }
--
2.26.2.266.ge870325ee8
