[PATCH 2/2] c++: Extend PR96204 fix to variable templates

[Patrick Palka via Gcc-patches]

r12-1829 corrected the access scope during partial specialization
matching of class templates, but neglected the variable template case.
This patch moves the access scope adjustment to inside
most_specialized_partial_spec, so that all callers can benefit.

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

        PR c++/96204

gcc/cp/ChangeLog:

        * pt.c (instantiate_class_template_1): Remove call to
        push_nested_class and pop_nested_class added by r12-1829.
        (most_specialized_partial_spec): Use push_access_scope_guard
        and deferring_access_check_sentinel.

gcc/testsuite/ChangeLog:

        * g++.dg/template/access40b.C: New test.
---
 gcc/cp/pt.c                               | 12 +++++++----
 gcc/testsuite/g++.dg/template/access40b.C | 26 +++++++++++++++++++++++
 2 files changed, 34 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/access40b.C

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index bd8b17ca047..1e2e2ba5329 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -11776,11 +11776,8 @@ instantiate_class_template_1 (tree type)
   deferring_access_check_sentinel acs (dk_no_deferred);
 
   /* Determine what specialization of the original template to
-     instantiate; do this relative to the scope of the class for
-     sake of access checking.  */
-  push_nested_class (type);
+     instantiate.  */
   t = most_specialized_partial_spec (type, tf_warning_or_error);
-  pop_nested_class ();
   if (t == error_mark_node)
     return error_mark_node;
   else if (t)
@@ -24989,26 +24986,33 @@ most_specialized_partial_spec (tree target, 
tsubst_flags_t complain)
   tree outer_args = NULL_TREE;
   tree tmpl, args;
 
+  tree decl;
   if (TYPE_P (target))
     {
       tree tinfo = CLASSTYPE_TEMPLATE_INFO (target);
       tmpl = TI_TEMPLATE (tinfo);
       args = TI_ARGS (tinfo);
+      decl = TYPE_NAME (target);
     }
   else if (TREE_CODE (target) == TEMPLATE_ID_EXPR)
     {
       tmpl = TREE_OPERAND (target, 0);
       args = TREE_OPERAND (target, 1);
+      decl = DECL_TEMPLATE_RESULT (tmpl);
     }
   else if (VAR_P (target))
     {
       tree tinfo = DECL_TEMPLATE_INFO (target);
       tmpl = TI_TEMPLATE (tinfo);
       args = TI_ARGS (tinfo);
+      decl = target;
     }
   else
     gcc_unreachable ();
 
+  push_access_scope_guard pas (decl);
+  deferring_access_check_sentinel acs (dk_no_deferred);
+
   tree main_tmpl = most_general_template (tmpl);
 
   /* For determining which partial specialization to use, only the
diff --git a/gcc/testsuite/g++.dg/template/access40b.C 
b/gcc/testsuite/g++.dg/template/access40b.C
new file mode 100644
index 00000000000..040e3d18096
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/access40b.C
@@ -0,0 +1,26 @@
+// PR c++/96204
+// { dg-do compile { target c++14 } }
+// A variant of access40.C where has_type_member is a variable template instead
+// of a class template.
+
+template<class, class = void>
+constexpr bool has_type_member = false;
+
+template<class T>
+constexpr bool has_type_member<T, typename T::type> = true;
+
+struct Parent;
+
+struct Child {
+private:
+  friend struct Parent;
+  typedef void type;
+};
+
+struct Parent {
+  static void f() {
+    // The partial specialization does not match despite Child::type
+    // being accessible from the current scope.
+    static_assert(!has_type_member<Child>, "");
+  }
+};
-- 
2.32.0.93.g670b81a890