From f58d5e069d601551cbc072919789e46f7fe3c77d Mon Sep 17 00:00:00 2001
From: Patrick Palka <ppalka@gcc.gnu.org>
Date: Wed, 1 Jul 2015 01:07:35 +0000
Subject: [PATCH] Fix PR c++/66686 (dependent template template substitution)

gcc/cp/ChangeLog:

	PR c++/66686
	* pt.c (coerce_template_template_parm) [PARM_DECL]: Don't
	return 0 if tsubst returns a dependent type.

gcc/testsuite/ChangeLog:

	PR c++/66686
	* g++.dg/template/pr66686.C: New test.

From-SVN: r225220
---
 gcc/cp/ChangeLog                        |  6 ++++++
 gcc/cp/pt.c                             | 12 +++++++-----
 gcc/testsuite/ChangeLog                 |  5 +++++
 gcc/testsuite/g++.dg/template/pr66686.C | 15 +++++++++++++++
 4 files changed, 33 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/pr66686.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 4d9b5a68cc4..e3436418259 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2015-07-01  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/66686
+	* pt.c (coerce_template_template_parm) [PARM_DECL]: Don't
+	return 0 if tsubst returns a dependent type.
+
 2015-06-30  Jason Merrill  <jason@redhat.com>
 
 	PR debug/66653
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 6b73d49ce29..38d2e3a24e3 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -6363,11 +6363,13 @@ coerce_template_template_parm (tree parm,
 	   D<int, C> d;
 
 	 i.e. the parameter list of TT depends on earlier parameters.  */
-      if (!uses_template_parms (TREE_TYPE (arg))
-	  && !same_type_p
-	        (tsubst (TREE_TYPE (parm), outer_args, complain, in_decl),
-		 TREE_TYPE (arg)))
-	return 0;
+      if (!uses_template_parms (TREE_TYPE (arg)))
+	{
+	  tree t = tsubst (TREE_TYPE (parm), outer_args, complain, in_decl);
+	  if (!uses_template_parms (t)
+	      && !same_type_p (t, TREE_TYPE (arg)))
+	    return 0;
+	}
       
       if (TEMPLATE_PARM_PARAMETER_PACK (DECL_INITIAL (arg))
 	  && !TEMPLATE_PARM_PARAMETER_PACK (DECL_INITIAL (parm)))
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8fc634abefd..aca88862aa9 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-07-01  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/66686
+	* g++.dg/template/pr66686.C: New test.
+
 2015-06-30  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gnat.dg/lto17.ad[sb]: New test.
diff --git a/gcc/testsuite/g++.dg/template/pr66686.C b/gcc/testsuite/g++.dg/template/pr66686.C
new file mode 100644
index 00000000000..d8aea625d46
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/pr66686.C
@@ -0,0 +1,15 @@
+// PR c++/66686
+
+template <int>
+struct Y { };
+
+template <class B, template <template <B> class Z> class C>
+struct X
+{
+  C<Y> a;  // { dg-bogus "mismatch" }
+};
+
+template <template <int> class>
+struct A { };
+
+X<int, A> a;
-- 
2.30.2