From b3cfa47d385c004bfbf1772c41e255e8eb60377e Mon Sep 17 00:00:00 2001
From: Patrick Palka <ppalka@redhat.com>
Date: Fri, 11 Aug 2023 13:26:02 -0400
Subject: [PATCH] c++: dependently scoped template-id in type-req [PR110927]
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Here we're incorrectly rejecting the first type-requirement at parse
time with
concepts-requires35.C:14:56: error: ‘typename A<T>::B’ is not a template [-fpermissive]
We also incorrectly reject the second type-requirement at satisfaction time
with
concepts-requires35.C:17:34: error: ‘typename A<int>::B’ names ‘template<class U> struct A<int>::B’, which is not a type
and similarly for the third type-requirement. This seems to happen only
within a type-requirement; if we instead use e.g. an alias template then
it works as expected.
The difference ultimately seems to be that during parsing of a using-decl,
we pass check_dependency_p=true to cp_parser_nested_name_specifier_opt
whereas for a type-requirement we pass check_dependency_p=false.
Passing =false causes cp_parser_template_id for the dependently-scoped
template-id B<bool> to create a TYPE_DECL of TYPENAME_TYPE (with
TYPENAME_IS_CLASS_P unexpectedly set in the last two cases) whereas
passing =true causes it to return a TEMPLATE_ID_EXPR. We then call
make_typename_type on this TYPE_DECL which does the wrong thing.
Since there seems to be no justification for using check_dependency_p=false
here, the simplest fix seems to be to pass check_dependency_p=true instead,
matching the behavior of cp_parser_elaborated_type_specifier.
PR c++/110927
gcc/cp/ChangeLog:
* parser.cc (cp_parser_type_requirement): Pass
check_dependency_p=true instead of =false.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-requires35.C: New test.
(cherry picked from commit 63bd36be990f3b08fcee5b69718ef97c055fbb31)
---
gcc/cp/parser.cc | 4 +--
.../g++.dg/cpp2a/concepts-requires35.C | 27 +++++++++++++++++++
2 files changed, 29 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires35.C
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 9c7a9a962289..b0cd1b463c82 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -30939,7 +30939,7 @@ cp_parser_type_requirement (cp_parser *parser)
cp_parser_global_scope_opt (parser, /*current_scope_valid_p=*/false);
cp_parser_nested_name_specifier_opt (parser,
/*typename_keyword_p=*/true,
- /*check_dependency_p=*/false,
+ /*check_dependency_p=*/true,
/*type_p=*/true,
/*is_declaration=*/false);
@@ -30949,7 +30949,7 @@ cp_parser_type_requirement (cp_parser *parser)
cp_lexer_consume_token (parser->lexer);
type = cp_parser_template_id (parser,
/*template_keyword_p=*/true,
- /*check_dependency=*/false,
+ /*check_dependency_p=*/true,
/*tag_type=*/none_type,
/*is_declaration=*/false);
type = make_typename_type (parser->scope, type, typename_type,
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires35.C b/gcc/testsuite/g++.dg/cpp2a/concepts-requires35.C
new file mode 100644
index 000000000000..7023019ea418
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires35.C
@@ -0,0 +1,27 @@
+// PR c++/110927
+// { dg-do compile { target c++20 } }
+
+template<class T>
+struct A {
+ template<class U> struct B { using type = B; };
+ template<class U> using type = U;
+};
+
+template<> struct A<void> { };
+
+template<class T>
+concept C1 = requires { typename A<T>::template B<bool>::type; };
+
+template<class T>
+concept C2 = requires { typename A<T>::template B<bool>; };
+
+template<class T>
+concept C3 = requires { typename A<T>::template type<bool>; };
+
+static_assert(C1<int>);
+static_assert(C2<int>);
+static_assert(C3<int>);
+
+static_assert(!C1<void>);
+static_assert(!C2<void>);
+static_assert(!C3<void>);
--
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