Re: [PATCH] c++: ->template and implicit typedef [PR104608]

[Jason Merrill <jason@redhat.com>]

On 2/22/22 17:46, Marek Polacek wrote:
> Here we have a forward declaration of Parameter for which we create
> an implicit typedef, which is a TYPE_DECL.  Then, when looking it up
> at template definition time, cp_parser_template_id gets (since r12-6754)
> this TYPE_DECL which it can't handle.

Hmm, getting that global TYPE_DECL from lookup seems like a bug; isn't 
the lookup earlier in cp_parser_template_name in object scope?

> This patch defers lookup for implicit typedefs, a la r12-6879.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> 
> 	PR c++/104608
> 
> gcc/cp/ChangeLog:
> 
> 	* parser.cc (cp_parser_template_name): Repeat lookup of implicit
> 	typedef.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/parse/template-keyword3.C: New test.
> ---
>   gcc/cp/parser.cc                               |  3 ++-
>   gcc/testsuite/g++.dg/parse/template-keyword3.C | 12 ++++++++++++
>   2 files changed, 14 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/parse/template-keyword3.C
> 
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index 03d99aba13e..5e89e3737b0 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -18681,7 +18681,8 @@ cp_parser_template_name (cp_parser* parser,
>   	  return error_mark_node;
>   	}
>         else if ((!DECL_P (decl) && !is_overloaded_fn (decl))
> -	       || TREE_CODE (decl) == USING_DECL)
> +	       || TREE_CODE (decl) == USING_DECL
> +	       || DECL_IMPLICIT_TYPEDEF_P (decl))
>   	/* Repeat the lookup at instantiation time.  */
>   	decl = identifier;
>       }
> diff --git a/gcc/testsuite/g++.dg/parse/template-keyword3.C b/gcc/testsuite/g++.dg/parse/template-keyword3.C
> new file mode 100644
> index 00000000000..59fe0fc180b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/parse/template-keyword3.C
> @@ -0,0 +1,12 @@
> +// PR c++/104608
> +
> +class Parameter;
> +template <typename R> class Function
> +: public R
> +{
> +    Function();
> +};
> +template <typename R>
> +Function<R>::Function() {
> +    this->template Parameter<R>();
> +}
> 
> base-commit: bc66b471d16ef2fd8cb66fd1131b41f80ecb9961