From c68e37efd8e9b9cb0c6ac8f27bb5f931ea17907e Mon Sep 17 00:00:00 2001
From: aoliva <aoliva@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu, 6 Dec 2018 23:18:40 +0000
Subject: [PATCH] [PR86747] tsubst friend tpl ctxt before looking it up for
 dupes

When a member template is redeclared as a friend, we enter the context
of the member before looking it up, and then we check that the decls
are compatible.  However, when the member template references template
types of the enclosing context, say an enclosing template class, the
compare fails because the friend decl is already tsubsted, whereas the
looked up name isn't.

The problem is that the enclosing context is taken from the friend
declaration before tsubsting it, so we look up in the context of the
generic template instead of that of the tsubsted one we're
specializing.  The solution is to tsubst the enclosing context when
it's a non-namespace scope.

for  gcc/cp/ChangeLog

	PR c++/86747
	* pt.c (tsubst_friend_class): Enter tsubsted class context.

for  gcc/testsuite/ChangeLog

	PR c++/86747
	* g++.dg/pr86747.C: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@266875 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/cp/ChangeLog               | 3 +++
 gcc/cp/pt.c                    | 5 ++++-
 gcc/testsuite/ChangeLog        | 3 +++
 gcc/testsuite/g++.dg/pr86747.C | 8 ++++++++
 4 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/pr86747.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 727f2d4f909f..e092c4490f55 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,8 @@
 2018-12-06  Alexandre Oliva <aoliva@redhat.com>
 
+	PR c++/86747
+	* pt.c (tsubst_friend_class): Enter tsubsted class context.
+
 	PR c++/86397
 	* except.c (build_noexcept_spec): Resolve nondependent
 	expressions.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 90fb3aee82d4..8560e5885933 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -10558,7 +10558,10 @@ tsubst_friend_class (tree friend_tmpl, tree args)
   if (TREE_CODE (context) == NAMESPACE_DECL)
     push_nested_namespace (context);
   else
-    push_nested_class (context);
+    {
+      context = tsubst (context, args, tf_error, NULL_TREE);
+      push_nested_class (context);
+    }
 
   tmpl = lookup_name_real (DECL_NAME (friend_tmpl), /*prefer_type=*/false,
 			   /*non_class=*/false, /*block_p=*/false,
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index eddb4576e0fd..1871663415ed 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2018-12-06  Alexandre Oliva <aoliva@redhat.com>
 
+	PR c++/86747
+	* g++.dg/pr86747.C: New.
+
 	PR c++/86397
 	* g++.dg/cpp0x/pr86397-1.C: New.
 	* g++.dg/cpp0x/pr86397-2.C: New.
diff --git a/gcc/testsuite/g++.dg/pr86747.C b/gcc/testsuite/g++.dg/pr86747.C
new file mode 100644
index 000000000000..5b0a0bb95146
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr86747.C
@@ -0,0 +1,8 @@
+// { dg-do compile }
+
+template <typename T> class A {
+  template <void (A::*p)()> class C; // #1
+  template <void (A::*q)()> friend class C; // #2
+};
+
+A<double> a;
-- 
2.47.2