Re: [C++ Patch] PR 57543

[Paolo Carlini]

... if the approach makes sense, we want to pass a proper in_decl in one 
more place, otherwise specializations are not handled (eg, K in the 
testcase). Like the below, lightly tested so far.

Paolo.
///////////////////////
Index: cp/pt.c
===================================================================
--- cp/pt.c     (revision 210956)
+++ cp/pt.c     (working copy)
@@ -1987,7 +1987,7 @@ determine_specialization (tree template_id,
            continue;
 
          /* Make sure that the deduced arguments actually work.  */
-         insttype = tsubst (TREE_TYPE (fn), targs, tf_none, NULL_TREE);
+         insttype = tsubst (TREE_TYPE (fn), targs, tf_none, fn);
          if (insttype == error_mark_node)
            continue;
          fn_arg_types
@@ -11323,7 +11323,28 @@ tsubst_function_type (tree t,
   gcc_assert (TYPE_CONTEXT (t) == NULL_TREE);
 
   /* Substitute the return type.  */
+  tree save_ccp = current_class_ptr;
+  tree save_ccr = current_class_ref;
+  bool do_inject = (!current_class_ref
+                   && TREE_CODE (t) == METHOD_TYPE
+                   && TREE_CODE (TREE_TYPE (t)) == DECLTYPE_TYPE);
+  if (do_inject)
+    {
+      /* DR 1207: 'this' is in scope in the trailing return type.  */
+      inject_this_parameter (current_class_type
+                            ? current_class_type
+                            : DECL_CONTEXT (in_decl),
+                            type_memfn_quals (t));
+    }
+
   return_type = tsubst (TREE_TYPE (t), args, complain, in_decl);
+
+  if (do_inject)
+    {
+      current_class_ptr = save_ccp;
+      current_class_ref = save_ccr;
+    }
+
   if (return_type == error_mark_node)
     return error_mark_node;
   /* DR 486 clarifies that creation of a function type with an
@@ -15872,7 +15893,7 @@ fn_type_unification (tree fn,
         access path at this point.  */
       push_deferring_access_checks (dk_deferred);
       fntype = tsubst (TREE_TYPE (fn), explicit_targs,
-                      complain | tf_partial, NULL_TREE);
+                      complain | tf_partial, fn);
       pop_deferring_access_checks ();
       input_location = loc;
       processing_template_decl -= incomplete;
Index: testsuite/g++.dg/cpp0x/decltype59.C
===================================================================
--- testsuite/g++.dg/cpp0x/decltype59.C (revision 0)
+++ testsuite/g++.dg/cpp0x/decltype59.C (working copy)
@@ -0,0 +1,41 @@
+// PR c++/57543
+// { dg-do compile { target c++11 } }
+
+template< typename > struct X
+{
+  void foo();
+  auto bar() -> decltype( X::foo() );
+};
+
+template< typename > struct Y
+{
+  void foo();
+  template< typename >
+  auto bar() -> decltype( Y::foo() );
+};
+
+template< typename > struct Z
+{
+  void foo();
+  template< typename T >
+  auto bar() -> decltype( T::foo() );
+};
+
+template< typename > struct K
+{
+  void foo();
+  template< typename T >
+  auto bar() -> decltype( T::foo() );
+};
+
+template<>
+template<>
+auto K<int>::bar<K<int>>() -> decltype( K<int>::foo() );
+
+int main()
+{
+  X<int>().bar();
+  Y<int>().bar<double>();
+  Z<int>().bar<Z<int>>();
+  K<int>().bar<K<int>>();
+}