Here when tentatively parsing the if condition as a declaration, we try
to treat C<1> as the start of a constrained placeholder type, which we
quickly reject because C doesn't accept a type as its first argument.
But since we're parsing tentatively, we shouldn't emit an error in this
case.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk/11?
PR c++/98394
gcc/cp/ChangeLog:
* parser.c (cp_parser_placeholder_type_specifier): Don't emit
a "does not constrain a type" error when parsing tentatively.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-pr98394.C: New test.
---
gcc/cp/parser.c | 7 +++++--
gcc/testsuite/g++.dg/cpp2a/concepts-pr98394.C | 14 ++++++++++++++
2 files changed, 19 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-pr98394.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 4c2075742d6..f1498e28da4 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -19909,8 +19909,11 @@ cp_parser_placeholder_type_specifier (cp_parser
*parser, location_t loc,
if (!flag_concepts_ts
|| !processing_template_parmlist)
{
- error_at (loc, "%qE does not constrain a type", DECL_NAME (con));
- inform (DECL_SOURCE_LOCATION (con), "concept defined here");
+ if (!tentative)
+ {
+ error_at (loc, "%qE does not constrain a type", DECL_NAME (con));
+ inform (DECL_SOURCE_LOCATION (con), "concept defined here");
+ }
return error_mark_node;
}
}
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr98394.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-pr98394.C
new file mode 100644
index 00000000000..c8407cdf7cd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr98394.C
@@ -0,0 +1,14 @@
+// PR c++/98394
+// { dg-do compile { target c++20 } }
+
+template<int...>
+concept C = true;
+
+template<int, int>
+concept D = true;
+
+int main() {
+ if (C<1>); // { dg-bogus "does not constrain a type" }
+ if (D<1>); // { dg-error "wrong number of template arguments" }
+ // { dg-bogus "does not constrain a type" "" { target *-*-* } .-1 }
+}
--
2.34.0.rc1.14.g88d915a634
