c++: concept in default argument [PR109859]
Checks
| Context |
Check |
Description |
| linaro-tcwg-bot/tcwg_gcc_build--master-arm |
success
|
Build passed
|
| linaro-tcwg-bot/tcwg_gcc_build--master-aarch64 |
success
|
Build passed
|
| linaro-tcwg-bot/tcwg_gcc_check--master-aarch64 |
success
|
Test passed
|
| linaro-tcwg-bot/tcwg_gcc_check--master-arm |
success
|
Test passed
|
Commit Message
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
1) We're hitting the assert in cp_parser_placeholder_type_specifier.
It says that if it turns out to be false, we should do error() instead.
Do so, then.
2) lambda-targ8.C should compile fine, though. The problem was that
local_variables_forbidden_p wasn't cleared when we're about to parse
the optional template-parameter-list for a lambda in a default argument.
PR c++/109859
gcc/cp/ChangeLog:
* parser.cc (cp_parser_lambda_declarator_opt): Temporarily clear
local_variables_forbidden_p.
(cp_parser_placeholder_type_specifier): Turn an assert into an error.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-defarg3.C: New test.
* g++.dg/cpp2a/lambda-targ8.C: New test.
---
gcc/cp/parser.cc | 9 +++++++--
gcc/testsuite/g++.dg/cpp2a/concepts-defarg3.C | 8 ++++++++
gcc/testsuite/g++.dg/cpp2a/lambda-targ8.C | 10 ++++++++++
3 files changed, 25 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-defarg3.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-targ8.C
base-commit: cc62b2c3da118f08f71d2ae9c08bafb55b35767a
Comments
On 9/18/24 5:06 PM, Marek Polacek wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>
> -- >8 --
> 1) We're hitting the assert in cp_parser_placeholder_type_specifier.
> It says that if it turns out to be false, we should do error() instead.
> Do so, then.
>
> 2) lambda-targ8.C should compile fine, though. The problem was that
> local_variables_forbidden_p wasn't cleared when we're about to parse
> the optional template-parameter-list for a lambda in a default argument.
>
> PR c++/109859
>
> gcc/cp/ChangeLog:
>
> * parser.cc (cp_parser_lambda_declarator_opt): Temporarily clear
> local_variables_forbidden_p.
> (cp_parser_placeholder_type_specifier): Turn an assert into an error.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp2a/concepts-defarg3.C: New test.
> * g++.dg/cpp2a/lambda-targ8.C: New test.
> ---
> gcc/cp/parser.cc | 9 +++++++--
> gcc/testsuite/g++.dg/cpp2a/concepts-defarg3.C | 8 ++++++++
> gcc/testsuite/g++.dg/cpp2a/lambda-targ8.C | 10 ++++++++++
> 3 files changed, 25 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-defarg3.C
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-targ8.C
>
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index 4dd9474cf60..bdc4fef243a 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -11891,6 +11891,11 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
> "lambda templates are only available with "
> "%<-std=c++20%> or %<-std=gnu++20%>");
>
> + /* Even though the whole lambda may be a default argument, its
> + template-parameter-list is a context where it's OK to create
> + new parameters. */
> + auto lvf = make_temp_override (parser->local_variables_forbidden_p, 0u);
> +
> cp_lexer_consume_token (parser->lexer);
>
> template_param_list = cp_parser_template_parameter_list (parser);
> @@ -20978,8 +20983,8 @@ cp_parser_placeholder_type_specifier (cp_parser *parser, location_t loc,
> /* In a default argument we may not be creating new parameters. */
> if (parser->local_variables_forbidden_p & LOCAL_VARS_FORBIDDEN)
> {
> - /* If this assert turns out to be false, do error() instead. */
> - gcc_assert (tentative);
> + if (!tentative)
> + error_at (loc, "local variables may not appear in this context");
There's no local variable in the new testcase, the error should talk
about a concept-name.
> return error_mark_node;
> }
> return build_constrained_parameter (con, proto, args);
> diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-defarg3.C b/gcc/testsuite/g++.dg/cpp2a/concepts-defarg3.C
> new file mode 100644
> index 00000000000..1d689dc8f30
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-defarg3.C
> @@ -0,0 +1,8 @@
> +// PR c++/109859
> +// { dg-do compile { target c++20 } }
> +
> +template<class>
> +concept C = true;
> +
> +template <class = C> // { dg-error "may not appear in this context" }
> +int f();
> diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-targ8.C b/gcc/testsuite/g++.dg/cpp2a/lambda-targ8.C
> new file mode 100644
> index 00000000000..3685b0ef880
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-targ8.C
> @@ -0,0 +1,10 @@
> +// PR c++/109859
> +// { dg-do compile { target c++20 } }
> +
> +template<typename>
> +concept A = true;
> +
> +template<auto = []<A a> {}>
> +int x;
> +
> +void g() { (void) x<>; }
>
> base-commit: cc62b2c3da118f08f71d2ae9c08bafb55b35767a
@@ -11891,6 +11891,11 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
"lambda templates are only available with "
"%<-std=c++20%> or %<-std=gnu++20%>");
+ /* Even though the whole lambda may be a default argument, its
+ template-parameter-list is a context where it's OK to create
+ new parameters. */
+ auto lvf = make_temp_override (parser->local_variables_forbidden_p, 0u);
+
cp_lexer_consume_token (parser->lexer);
template_param_list = cp_parser_template_parameter_list (parser);
@@ -20978,8 +20983,8 @@ cp_parser_placeholder_type_specifier (cp_parser *parser, location_t loc,
/* In a default argument we may not be creating new parameters. */
if (parser->local_variables_forbidden_p & LOCAL_VARS_FORBIDDEN)
{
- /* If this assert turns out to be false, do error() instead. */
- gcc_assert (tentative);
+ if (!tentative)
+ error_at (loc, "local variables may not appear in this context");
return error_mark_node;
}
return build_constrained_parameter (con, proto, args);
new file mode 100644
@@ -0,0 +1,8 @@
+// PR c++/109859
+// { dg-do compile { target c++20 } }
+
+template<class>
+concept C = true;
+
+template <class = C> // { dg-error "may not appear in this context" }
+int f();
new file mode 100644
@@ -0,0 +1,10 @@
+// PR c++/109859
+// { dg-do compile { target c++20 } }
+
+template<typename>
+concept A = true;
+
+template<auto = []<A a> {}>
+int x;
+
+void g() { (void) x<>; }