[PATCH] c++: fix lookup into enclosing scope when instantiating nested class bases

[Jason Merrill]

On 9/1/26 3:34 AM, imlunex2011@gmail.com wrote:
> From: Lunex <imlunex2011@gmail.com>

Thanks for the patch!  I'm pushing it with some adjustments.

This patch is trivial enough not to worry about copyright, but if you 
want to continue contributing under this pseudonym I encourage you to 
file a copyright assignment with the FSF.  See 
https://gcc.gnu.org/contribute.html#legal for more information.

> PR c++/114804

For future reference, the PR number should go at the top of the 
ChangeLog entries.
> r11-6815 (PR 82613) removed push_scope/pop_scope around base-clause
> substitution in instantiate_class_template. This broke lookup for
> using-declarations that bring enclosing-class members into scope
> during nested class instantiation.
> 
> This restores the enclosing-class scope push/pop that was there before
> r11-6815.
> 
> gcc/cp/ChangeLog:
> 	* pt.cc (instantiate_class_template): Push enclosing class scope
> 	before base substitution, pop after.
> 
> gcc/testsuite/ChangeLog:
> 	* g++.dg/template/pr114804.C: New test.

And please name testcases by what they are testing, not just the PR; 
I've renamed it to dependent-base7.C.

> @@ -13093,6 +13096,9 @@ instantiate_class_template (tree type)
>       information.  */
>    xref_basetypes (type, base_list);
>  
> +  if (pushed_scope)
> +    pop_scope (pushed_scope);
> +
>    apply_late_template_attributes (&type, TYPE_ATTRIBUTES (pattern),
>  				  (int) ATTR_FLAG_TYPE_IN_PLACE,
>  				  args, tf_error, NULL_TREE);

It occurred to me that rather than pop all the way out and then almost 
immediately push_nested_class again, we could stay in the enclosing 
scope and only push one level into the class we're defining.

> +++ b/gcc/testsuite/g++.dg/template/pr114804.C
> @@ -0,0 +1,21 @@
> +// PR c++/114804
> +// { dg-do compile }

Also this needs { target c++11 } to avoid FAILing in C++98 mode.  How 
did you test the patch?

Here's what I'm pushing:

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