[pushed] c++: elaborated-type-spec in requires-expr [PR101677]
Commit Message
We were failing to declare class S in the global namespace because we were
treating the requires-expression parameter scope as a normal block scope, so
the implicit declaration went there.
It seems to me that the requires parameter scope is more like a function
parameter scope (not least in the use of the word "parameter"), so let's
change the scope kind. But then we need to adjust the prohibition on
placeholders declaring implicit template parameters.
Tested x86_64-pc-linux-gnu, applying to trunk.
PR c++/101677
gcc/cp/ChangeLog:
* name-lookup.h (struct cp_binding_level): Add requires_expression
bit-field.
* name-lookup.cc (pushtag): Check it.
* parser.cc (cp_parser_requires_expression): Set it.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-requires28.C: New test.
---
gcc/cp/name-lookup.h | 5 ++++-
gcc/cp/parser.cc | 5 +++--
gcc/testsuite/g++.dg/cpp2a/concepts-pr67178.C | 2 +-
gcc/testsuite/g++.dg/cpp2a/concepts-requires28.C | 13 +++++++++++++
4 files changed, 21 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires28.C
base-commit: 5c8d22b00adedc21f8b697dd6b990f4821a06634
@@ -309,7 +309,10 @@ struct GTY(()) cp_binding_level {
/* true for SK_FUNCTION_PARMS of immediate functions. */
unsigned immediate_fn_ctx_p : 1;
- /* 22 bits left to fill a 32-bit word. */
+ /* True for SK_FUNCTION_PARMS of a requires-expression. */
+ unsigned requires_expression: 1;
+
+ /* 21 bits left to fill a 32-bit word. */
};
/* The binding level currently in effect. */
@@ -29964,7 +29964,8 @@ cp_parser_requires_expression (cp_parser *parser)
scope_sentinel ()
{
++cp_unevaluated_operand;
- begin_scope (sk_block, NULL_TREE);
+ begin_scope (sk_function_parms, NULL_TREE);
+ current_binding_level->requires_expression = true;
}
~scope_sentinel ()
@@ -48082,7 +48083,7 @@ static tree
synthesize_implicit_template_parm (cp_parser *parser, tree constr)
{
/* A requires-clause is not a function and cannot have placeholders. */
- if (current_binding_level->kind == sk_block)
+ if (current_binding_level->requires_expression)
{
error ("placeholder type not allowed in this context");
return error_mark_node;
@@ -12,7 +12,7 @@ concept C0 = requires (auto x) { // { dg-error "placeholder type" }
template<typename T>
concept C1 = requires (C1 auto x) { // { dg-error "not been declared|placeholder|two or more|in requirements" }
x; // { dg-error "not declared" }
- { x } -> c; // { dg-message "is invalid" }
+ { x } -> c; // { dg-message "is invalid|not declared" }
};
template<typename T>
new file mode 100644
@@ -0,0 +1,13 @@
+// PR c++/101677
+// { dg-do compile { target c++20 } }
+
+template<class T>
+concept C_bug_with_forward_decl = requires(T& t){
+ t.template f<class S>();
+};
+
+struct good {
+ template<class T> void f() {}
+};
+
+static_assert(C_bug_with_forward_decl<good>);