Bootstrapped and tested on x86_64-pc-linux-gnu. -- 8< --
This patch raises an error early when the decltype(auto) specifier is used as a parameter of a function. This prevents any issues with an unexpected tree type later on when performing the call. PR 103497 gcc/cp/ChangeLog: * parser.cc (cp_parser_simple_type_specifier): Add check for decltype(auto) as function parameter. gcc/testsuite/ChangeLog: * g++.dg/pr103497.C: New test. Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com> --- gcc/cp/parser.cc | 10 ++++++++++ gcc/testsuite/g++.dg/pr103497.C | 7 +++++++ 2 files changed, 17 insertions(+) create mode 100644 gcc/testsuite/g++.dg/pr103497.C diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc index e5f032f2330..1415e07e152 100644 --- a/gcc/cp/parser.cc +++ b/gcc/cp/parser.cc @@ -19884,6 +19884,16 @@ cp_parser_simple_type_specifier (cp_parser* parser, && cp_lexer_peek_nth_token (parser->lexer, 2)->type != CPP_SCOPE) { type = saved_checks_value (token->u.tree_check_value); + /* Within a function parameter declaration, decltype(auto) is always an + error. */ + if (parser->auto_is_implicit_function_template_parm_p + && TREE_CODE (type) == TEMPLATE_TYPE_PARM + && AUTO_IS_DECLTYPE (type)) + { + error_at (token->location, + "cannot declare a parameter with %<decltype(auto)%>"); + type = error_mark_node; + } if (decl_specs) { cp_parser_set_decl_spec_type (decl_specs, type, diff --git a/gcc/testsuite/g++.dg/pr103497.C b/gcc/testsuite/g++.dg/pr103497.C new file mode 100644 index 00000000000..bcd421c2907 --- /dev/null +++ b/gcc/testsuite/g++.dg/pr103497.C @@ -0,0 +1,7 @@ +// { dg-do compile { target c++14 } } + +void foo(decltype(auto)... args); // { dg-error "parameter with .decltype.auto..|no parameter packs" } + +int main() { + foo(); +} -- 2.34.1