On Sun, 2 Mar 2025, Da Xie wrote:
> Add check for constrained auto type specifier in function declaration or
> function type declaration with trailing return type. Issue error if such
> usage is detected.
>
> Test file renamed, and added a new test for type declaration.
>
> Successfully bootstrapped and regretested on x86_64-pc-linux-gnu:
> Added 6 passed and 4 unsupported tests.
>
> PR c++/100589
>
> gcc/cp/ChangeLog:
>
> * decl.cc (grokdeclarator): Issue an error for a declarator with
> constrained auto type specifier and trailing return types. Include
> function names if available.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp2a/concepts-pr100589.C: New test.
LGTM, thanks! Jason, shall I push this to trunk?
>
> Signed-off-by: Da Xie <xxie...@163.com>
> ---
> gcc/cp/decl.cc | 13 +++++++++++++
> gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C | 9 +++++++++
> 2 files changed, 22 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
>
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 9ca8c6c4481..337ee65752e 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -14037,6 +14037,19 @@ grokdeclarator (const cp_declarator *declarator,
> "invalid use of %<decltype(auto)%>");
> return error_mark_node;
> }
> + else if (is_constrained_auto (type))
> + {
> + if (funcdecl_p)
> + error_at (typespec_loc,
> + "%qs function with trailing return type "
> + "has constrained %<auto%> type specifier "
> + "rather than plain %<auto%>",
> + name);
> + else
> + error_at (typespec_loc,
> + "invalid use of constrained %<auto%> type");
> + return error_mark_node;
> + }
> tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node);
> if (!tmpl)
> if (tree late_auto = type_uses_auto (late_return_type))
> diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
> b/gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
> new file mode 100644
> index 00000000000..0c60d31f29b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
> @@ -0,0 +1,9 @@
> +// PR c++/100589
> +// { dg-do compile { target c++20 } }
> +
> +template<class T>
> +concept false_concept = false;
> +
> +false_concept auto f() -> int; // { dg-error "'f' .* trailing return type.*
> constrained 'auto'" }
I can replace the use of .* with \[^\r\n\]* before pushing.
> +
> +using type = false_concept auto() -> int; // { dg-error "invalid use of
> constrained 'auto' type"}
> --
> 2.34.1
>
>
