c++: make finish non_static_data_member SFINAE friendly [PR105351]

  Here, since finish_non_static_data_member isn't SFINAE friendly, we
incorrectly emit an error during overload resolution:

sfinae33.C: In substitution of ‘template<class T> A<T::value> f() [with T = B]’:
sfinae33.C:11:7:   required from here
sfinae33.C:5:31: error: invalid use of non-static data member ‘B::value’
    5 | template<class T> A<T::value> f();
      |                               ^

This patch fixes this by making the function SFINAE friendly in the
usual way: give it a complain parameter, check it before emitting an
error, and pass it through appropriately.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?

	PR c++/105351

gcc/cp/ChangeLog:

	* cp-tree.h (finish_non_static_data_member): Add defaulted
	complain parameter.
	* pt.cc (tsubst_copy_and_build): Pass complain to
	finish_non_static_data_member.
	* semantics.cc (finish_non_static_data_member): Respect complain
	parameter.
	(finish_qualified_id_expr): Pass complain to
	finish_non_static_data_member.

gcc/testsuite/ChangeLog:

	* g++.dg/template/sfinae33.C: New test.
---
 gcc/cp/cp-tree.h                         |  3 ++-
 gcc/cp/pt.cc                             |  3 ++-
 gcc/cp/semantics.cc                      | 27 ++++++++++++++----------
 gcc/testsuite/g++.dg/template/sfinae33.C | 12 +++++++++++
 4 files changed, 32 insertions(+), 13 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/sfinae33.C
  

On 5/3/22 13:40, Patrick Palka wrote:
> Here, since finish_non_static_data_member isn't SFINAE friendly, we
> incorrectly emit an error during overload resolution:
> 
> sfinae33.C: In substitution of ‘template<class T> A<T::value> f() [with T = B]’:
> sfinae33.C:11:7:   required from here
> sfinae33.C:5:31: error: invalid use of non-static data member ‘B::value’
>      5 | template<class T> A<T::value> f();
>        |                               ^
> 
> This patch fixes this by making the function SFINAE friendly in the
> usual way: give it a complain parameter, check it before emitting an
> error, and pass it through appropriately.
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?

OK.

> 	PR c++/105351
> 
> gcc/cp/ChangeLog:
> 
> 	* cp-tree.h (finish_non_static_data_member): Add defaulted
> 	complain parameter.
> 	* pt.cc (tsubst_copy_and_build): Pass complain to
> 	finish_non_static_data_member.
> 	* semantics.cc (finish_non_static_data_member): Respect complain
> 	parameter.
> 	(finish_qualified_id_expr): Pass complain to
> 	finish_non_static_data_member.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/template/sfinae33.C: New test.
> ---
>   gcc/cp/cp-tree.h                         |  3 ++-
>   gcc/cp/pt.cc                             |  3 ++-
>   gcc/cp/semantics.cc                      | 27 ++++++++++++++----------
>   gcc/testsuite/g++.dg/template/sfinae33.C | 12 +++++++++++
>   4 files changed, 32 insertions(+), 13 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/template/sfinae33.C
> 
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 72177999968..b29e60ee52f 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -7615,7 +7615,8 @@ inline tree force_paren_expr_uneval 		(tree t)
>   { return force_paren_expr (t, true); }
>   extern tree maybe_undo_parenthesized_ref	(tree);
>   extern tree maybe_strip_ref_conversion		(tree);
> -extern tree finish_non_static_data_member       (tree, tree, tree);
> +extern tree finish_non_static_data_member       (tree, tree, tree,
> +						 tsubst_flags_t = tf_warning_or_error);
>   extern tree begin_stmt_expr			(void);
>   extern tree finish_stmt_expr_expr		(tree, tree);
>   extern tree finish_stmt_expr			(tree, bool);
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 81c3c598c71..f96f8e31885 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -21059,7 +21059,8 @@ tsubst_copy_and_build (tree t,
>   	  }
>   	else if (TREE_CODE (member) == FIELD_DECL)
>   	  {
> -	    r = finish_non_static_data_member (member, object, NULL_TREE);
> +	    r = finish_non_static_data_member (member, object, NULL_TREE,
> +					       complain);
>   	    if (TREE_CODE (r) == COMPONENT_REF)
>   	      REF_PARENTHESIZED_P (r) = REF_PARENTHESIZED_P (t);
>   	    RETURN (r);
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index 377f61113c0..bfb737f665b 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -2141,7 +2141,8 @@ finish_parenthesized_expr (cp_expr expr)
>      preceded by `.' or `->'.  */
>   
>   tree
> -finish_non_static_data_member (tree decl, tree object, tree qualifying_scope)
> +finish_non_static_data_member (tree decl, tree object, tree qualifying_scope,
> +			       tsubst_flags_t complain /* = tf_warning_or_error */)
>   {
>     gcc_assert (TREE_CODE (decl) == FIELD_DECL);
>     bool try_omp_private = !object && omp_private_member_map;
> @@ -2172,12 +2173,15 @@ finish_non_static_data_member (tree decl, tree object, tree qualifying_scope)
>     if (is_dummy_object (object) && cp_unevaluated_operand == 0
>         && (!processing_template_decl || !current_class_ref))
>       {
> -      if (current_function_decl
> -	  && DECL_STATIC_FUNCTION_P (current_function_decl))
> -	error ("invalid use of member %qD in static member function", decl);
> -      else
> -	error ("invalid use of non-static data member %qD", decl);
> -      inform (DECL_SOURCE_LOCATION (decl), "declared here");
> +      if (complain & tf_error)
> +	{
> +	  if (current_function_decl
> +	      && DECL_STATIC_FUNCTION_P (current_function_decl))
> +	    error ("invalid use of member %qD in static member function", decl);
> +	  else
> +	    error ("invalid use of non-static data member %qD", decl);
> +	  inform (DECL_SOURCE_LOCATION (decl), "declared here");
> +	}
>   
>         return error_mark_node;
>       }
> @@ -2219,8 +2223,9 @@ finish_non_static_data_member (tree decl, tree object, tree qualifying_scope)
>       {
>         tree access_type = TREE_TYPE (object);
>   
> -      perform_or_defer_access_check (TYPE_BINFO (access_type), decl,
> -				     decl, tf_warning_or_error);
> +      if (!perform_or_defer_access_check (TYPE_BINFO (access_type), decl,
> +					  decl, complain))
> +	return error_mark_node;
>   
>         /* If the data member was named `C::M', convert `*this' to `C'
>   	 first.  */
> @@ -2234,7 +2239,7 @@ finish_non_static_data_member (tree decl, tree object, tree qualifying_scope)
>         ret = build_class_member_access_expr (object, decl,
>   					    /*access_path=*/NULL_TREE,
>   					    /*preserve_reference=*/false,
> -					    tf_warning_or_error);
> +					    complain);
>       }
>     if (try_omp_private)
>       {
> @@ -2396,7 +2401,7 @@ finish_qualified_id_expr (tree qualifying_class,
>       {
>         push_deferring_access_checks (dk_no_check);
>         expr = finish_non_static_data_member (expr, NULL_TREE,
> -					    qualifying_class);
> +					    qualifying_class, complain);
>         pop_deferring_access_checks ();
>       }
>     else if (BASELINK_P (expr))
> diff --git a/gcc/testsuite/g++.dg/template/sfinae33.C b/gcc/testsuite/g++.dg/template/sfinae33.C
> new file mode 100644
> index 00000000000..cb9d4982211
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/sfinae33.C
> @@ -0,0 +1,12 @@
> +// PR c++/105351
> +
> +template<int> struct A;
> +
> +template<class T> A<T::value> f();
> +template<class T> void f();
> +
> +struct B { int value; };
> +
> +int main() {
> +  f<B>();
> +}