commit 4c44bea1d8228188db87478e418df7e10921b7c8
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Apr 12 09:58:39 2013 -0400

    gcc/cp/
    	* pt.c (fn_type_unification): Push tinst level around
    	type_unification_real if we aren't explaining.
    	* cp-tree.h (TFF_NO_TEMPLATE_BINDINGS): New.
    	* error.c (dump_function_decl): Respect it.
    	(subst_to_string): Pass it.
    libstdc++-v3/
    	* testsuite/lib/prune.exp (libstdc++-dg-prune): Also ignore "In
    	substitution" lines.

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index a5c7548..d96340a 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -4636,7 +4636,9 @@ enum overload_flags { NO_SPECIAL = 0, DTOR_FLAG, TYPENAME_FLAG };
    TFF_UNQUALIFIED_NAME: do not print the qualifying scope of the
        top-level entity.
    TFF_NO_OMIT_DEFAULT_TEMPLATE_ARGUMENTS: do not omit template arguments
-       identical to their defaults.  */
+       identical to their defaults.
+   TFF_NO_TEMPLATE_BINDINGS: do not print information about the template
+       arguments for a function template specialization.  */
 
 #define TFF_PLAIN_IDENTIFIER			(0)
 #define TFF_SCOPE				(1)
@@ -4652,6 +4654,7 @@ enum overload_flags { NO_SPECIAL = 0, DTOR_FLAG, TYPENAME_FLAG };
 #define TFF_NO_FUNCTION_ARGUMENTS		(1 << 10)
 #define TFF_UNQUALIFIED_NAME			(1 << 11)
 #define TFF_NO_OMIT_DEFAULT_TEMPLATE_ARGUMENTS	(1 << 12)
+#define TFF_NO_TEMPLATE_BINDINGS		(1 << 13)
 
 /* Returns the TEMPLATE_DECL associated to a TEMPLATE_TEMPLATE_PARM
    node.  */
diff --git a/gcc/cp/error.c b/gcc/cp/error.c
index 3206342..7a8c0bc 100644
--- a/gcc/cp/error.c
+++ b/gcc/cp/error.c
@@ -1451,7 +1451,8 @@ dump_function_decl (tree t, int flags)
 	dump_type_suffix (TREE_TYPE (fntype), flags);
 
       /* If T is a template instantiation, dump the parameter binding.  */
-      if (template_parms != NULL_TREE && template_args != NULL_TREE)
+      if (template_parms != NULL_TREE && template_args != NULL_TREE
+	  && !(flags & TFF_NO_TEMPLATE_BINDINGS))
 	{
 	  pp_cxx_whitespace (cxx_pp);
 	  pp_cxx_left_bracket (cxx_pp);
@@ -2889,7 +2890,8 @@ subst_to_string (tree p)
   tree decl = TREE_PURPOSE (p);
   tree targs = TREE_VALUE (p);
   tree tparms = DECL_TEMPLATE_PARMS (decl);
-  int flags = TFF_DECL_SPECIFIERS|TFF_TEMPLATE_HEADER;
+  int flags = (TFF_DECL_SPECIFIERS|TFF_TEMPLATE_HEADER
+	       |TFF_NO_TEMPLATE_BINDINGS);
 
   if (p == NULL_TREE)
     return "";
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 6ce2770..855c1f7 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -15125,9 +15125,21 @@ fn_type_unification (tree fn,
      callers must be ready to deal with unification failures in any
      event.  */
 
+  TREE_VALUE (tinst) = targs;
+  /* If we aren't explaining yet, push tinst context so we can see where
+     any errors (e.g. from class instantiations triggered by instantiation
+     of default template arguments) come from.  If we are explaining, this
+     context is redundant.  */
+  if (!explain_p && !push_tinst_level (tinst))
+    {
+      excessive_deduction_depth = true;
+      goto fail;
+    }
   ok = !type_unification_real (DECL_INNERMOST_TEMPLATE_PARMS (fn),
 			       targs, parms, args, nargs, /*subr=*/0,
 			       strict, flags, explain_p);
+  if (!explain_p)
+    pop_tinst_level ();
   if (!ok)
     goto fail;
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg5.C b/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg5.C
new file mode 100644
index 0000000..0821fc0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg5.C
@@ -0,0 +1,17 @@
+// Only print template subst context when it isn't redundant.
+// { dg-require-effective-target c++11 }
+// { dg-prune-output "error" }
+
+template<class T> struct A { typedef typename T::type type; };
+
+template <class T, class U = typename A<T>::type>
+void f(T);
+
+template <class T, class U = typename T::type>
+void g(T);
+
+int main()
+{
+  f(1);				// { dg-message "required from here" }
+  g(1);				// { dg-bogus "required from here" }
+}
diff --git a/libstdc++-v3/testsuite/lib/prune.exp b/libstdc++-v3/testsuite/lib/prune.exp
index b17fa00..6ed3efb 100644
--- a/libstdc++-v3/testsuite/lib/prune.exp
+++ b/libstdc++-v3/testsuite/lib/prune.exp
@@ -42,7 +42,7 @@ proc libstdc++-dg-prune { system text } {
 
     # Remove parts of warnings that refer to location of previous
     # definitions, etc as these confuse dejagnu
-    regsub -all "(^|\n)(\[^\n\]*: )?In ((static member |lambda )?function|member|method|(copy )?constructor|destructor|instantiation|program|subroutine|block-data)\[^\n\]*" $text "" text
+    regsub -all "(^|\n)(\[^\n\]*: )?In ((static member |lambda )?function|member|method|(copy )?constructor|destructor|instantiation|substitution|program|subroutine|block-data)\[^\n\]*" $text "" text
     regsub -all "(^|\n)\[^\n\]*(: )?At (top level|global scope):\[^\n\]*" $text "" text
     regsub -all "(^|\n)\[^\n\]*:   (recursively )?required \[^\n\]*" $text "" text
     regsub -all "(^|\n)\[^\n\]*:   . skipping \[0-9\]* instantiation contexts \[^\n\]*" $text "" text
