https://gcc.gnu.org/g:81db6857686c2d7932949afb948419a575bc0b3f
commit r14-10548-g81db6857686c2d7932949afb948419a575bc0b3f Author: Patrick Palka <ppa...@redhat.com> Date: Mon Jul 29 16:37:19 2024 -0400 c++: generic lambda in default template argument [PR88313] Here we're rejecting the generic lambda inside the default template argument ultimately because auto_is_implicit_function_template_parm_p doesn't get set during parsing of the lambda's parameter list, due to the !processing_template_parmlist restriction. But when parsing a lambda parameter list we should always set that flag regardless of where the lambda appears. This patch makes sure of this via a local lambda_p flag. PR c++/88313 gcc/cp/ChangeLog: * parser.cc (cp_parser_lambda_declarator_opt): Pass lambda_p=true to cp_parser_parameter_declaration_clause. (cp_parser_direct_declarator): Pass lambda_p=false to to cp_parser_parameter_declaration_clause. (cp_parser_parameter_declaration_clause): Add bool lambda_p parameter. Consider lambda_p instead of current_class_type when setting parser->auto_is_implicit_function_template_parm_p. Don't consider processing_template_parmlist. (cp_parser_requirement_parameter_list): Pass lambda_p=false to cp_parser_parameter_declaration_clause. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/lambda-targ6.C: New test. Reviewed-by: Jason Merrill <ja...@redhat.com> (cherry picked from commit 72a7ab891ae0061841c4eb641ef6ab7719bf0369) Diff: --- gcc/cp/parser.cc | 34 ++++++++++++++++++------------- gcc/testsuite/g++.dg/cpp2a/lambda-targ6.C | 15 ++++++++++++++ 2 files changed, 35 insertions(+), 14 deletions(-) diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc index 7e81c1010c45..00cf128522a7 100644 --- a/gcc/cp/parser.cc +++ b/gcc/cp/parser.cc @@ -2598,7 +2598,7 @@ static tree cp_parser_type_id_1 static void cp_parser_type_specifier_seq (cp_parser *, cp_parser_flags, bool, bool, cp_decl_specifier_seq *); static tree cp_parser_parameter_declaration_clause - (cp_parser *, cp_parser_flags); + (cp_parser *, cp_parser_flags, bool); static tree cp_parser_parameter_declaration_list (cp_parser *, cp_parser_flags, auto_vec<tree> *); static cp_parameter_declarator *cp_parser_parameter_declaration @@ -11867,7 +11867,7 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr) /* Parse parameters. */ param_list = cp_parser_parameter_declaration_clause - (parser, CP_PARSER_FLAGS_TYPENAME_OPTIONAL); + (parser, CP_PARSER_FLAGS_TYPENAME_OPTIONAL, /*lambda_p=*/true); /* Default arguments shall not be specified in the parameter-declaration-clause of a lambda-declarator. */ @@ -23903,7 +23903,8 @@ cp_parser_direct_declarator (cp_parser* parser, /* Parse the parameter-declaration-clause. */ params - = cp_parser_parameter_declaration_clause (parser, flags); + = cp_parser_parameter_declaration_clause (parser, flags, + /*lambda_p=*/false); const location_t parens_end = cp_lexer_peek_token (parser->lexer)->location; @@ -25252,13 +25253,17 @@ function_being_declared_is_template_p (cp_parser* parser) The parser flags FLAGS is used to control type-specifier parsing. + LAMBDA_P is true if this is the parameter-declaration-clause of + a lambda-declarator. + Returns a representation for the parameter declarations. A return value of NULL indicates a parameter-declaration-clause consisting only of an ellipsis. */ static tree cp_parser_parameter_declaration_clause (cp_parser* parser, - cp_parser_flags flags) + cp_parser_flags flags, + bool lambda_p) { tree parameters; cp_token *token; @@ -25267,15 +25272,15 @@ cp_parser_parameter_declaration_clause (cp_parser* parser, auto cleanup = make_temp_override (parser->auto_is_implicit_function_template_parm_p); - if (!processing_specialization - && !processing_template_parmlist - && !processing_explicit_instantiation - /* default_arg_ok_p tracks whether this is a parameter-clause for an - actual function or a random abstract declarator. */ - && parser->default_arg_ok_p) - if (!current_function_decl - || (current_class_type && LAMBDA_TYPE_P (current_class_type))) - parser->auto_is_implicit_function_template_parm_p = true; + if (lambda_p + || (!processing_specialization + && !processing_template_parmlist + && !processing_explicit_instantiation + /* default_arg_ok_p tracks whether this is a parameter-clause for an + actual function or a random abstract declarator. */ + && parser->default_arg_ok_p + && !current_function_decl)) + parser->auto_is_implicit_function_template_parm_p = true; /* Peek at the next token. */ token = cp_lexer_peek_token (parser->lexer); @@ -31472,7 +31477,8 @@ cp_parser_requirement_parameter_list (cp_parser *parser) return error_mark_node; tree parms = (cp_parser_parameter_declaration_clause - (parser, CP_PARSER_FLAGS_TYPENAME_OPTIONAL)); + (parser, CP_PARSER_FLAGS_TYPENAME_OPTIONAL, + /*lambda_p=*/false)); if (!parens.require_close (parser)) return error_mark_node; diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-targ6.C b/gcc/testsuite/g++.dg/cpp2a/lambda-targ6.C new file mode 100644 index 000000000000..51728a040e25 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-targ6.C @@ -0,0 +1,15 @@ +// PR c++/88313 +// { dg-do compile { target c++20 } } + +template<int N = [](auto x) { return x; }(42)> +constexpr int f() { return N; } + +template<auto F = [](auto x) { return x; }> +constexpr auto g() { return F; } + +template<class T = decltype([](auto x) { return x; })> +constexpr int h(T t = {}) { return t(42); } + +static_assert(f() == 42); +static_assert(g()(42) == 42); +static_assert(h() == 42);