From patchwork Thu Dec  6 14:26:31 2012
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Subject: C++ PATCH for c++/54653 (ICE with missing template-header)
Date: Thu, 06 Dec 2012 04:26:31 -0000
From: Jason Merrill <jason@redhat.com>
X-Patchwork-Id: 204242
Message-Id: <50C0AB17.6010808@redhat.com>
To: gcc-patches List <gcc-patches@gcc.gnu.org>

In this PR, we have a partial specialization of a member of a partial 
specialization, and we were confused into thinking that we only needed 
one template-header.  The parser.c hunk makes us generate the 
appropriate error.

The pt.c hunks fix the compiler to deal with it properly if it had been 
valid, since I expect we will allow explicit specialization of members 
of templates in the future.

Tested x86_64-pc-linux-gnu, applying to trunk.


commit 1633b5ae07f673a578393fae691d7c4f3f7bf9bb
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Dec 5 16:24:26 2012 -0500

    	PR c++/54653
    	* parser.c (cp_parser_class_head): A partial specialization scope
    	counts as a template.
    	* pt.c (tsubst_template_parms): Handle template template parm parms.
    	(tsubst_decl) [TEMPLATE_DECL]: Handle getting a template template
    	argument back.

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 1fe6246..190b8d9 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -18589,7 +18589,8 @@ cp_parser_class_head (cp_parser* parser,
 		&& CLASS_TYPE_P (scope)
 		&& CLASSTYPE_TEMPLATE_INFO (scope)
 		&& PRIMARY_TEMPLATE_P (CLASSTYPE_TI_TEMPLATE (scope))
-		&& !CLASSTYPE_TEMPLATE_SPECIALIZATION (scope))
+		&& (!CLASSTYPE_TEMPLATE_SPECIALIZATION (scope)
+		    || uses_template_parms (CLASSTYPE_TI_ARGS (scope))))
 	      ++num_templates;
 	}
     }
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 27084a2..c1e12f0 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -9552,7 +9552,7 @@ tsubst_template_parms (tree parms, tree args, tsubst_flags_t complain)
   ++processing_template_decl;
 
   for (new_parms = &r;
-       TMPL_PARMS_DEPTH (parms) > TMPL_ARGS_DEPTH (args);
+       parms && TMPL_PARMS_DEPTH (parms) > TMPL_ARGS_DEPTH (args);
        new_parms = &(TREE_CHAIN (*new_parms)),
 	 parms = TREE_CHAIN (parms))
     {
@@ -9831,6 +9831,10 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
 	    tree new_type = tsubst (TREE_TYPE (t), args, complain, in_decl);
 	    if (new_type == error_mark_node)
 	      RETURN (error_mark_node);
+	    /* If we get a real template back, return it.  This can happen in
+	       the context of most_specialized_class.  */
+	    if (TREE_CODE (new_type) == TEMPLATE_DECL)
+	      return new_type;
 
 	    r = copy_decl (t);
 	    DECL_CHAIN (r) = NULL_TREE;
diff --git a/gcc/testsuite/g++.dg/template/partial-specialization2.C b/gcc/testsuite/g++.dg/template/partial-specialization2.C
new file mode 100644
index 0000000..c22d739
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/partial-specialization2.C
@@ -0,0 +1,8 @@
+// PR c++/54653
+
+template <class T> struct A;
+template <class T> struct A<T*> {
+  template <class U> struct B;
+};
+
+template <class T> struct A<T*>::B<T*> { }; // { dg-error "too few template-parameter-lists" }