Fix result type checking of factory constructors of generic classes in VM.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 14760)
+++ runtime/vm/parser.cc	(working copy)
@@ -3017,6 +3017,11 @@
   if (IsIdentifier() &&
       (CurrentLiteral()->Equals(members->class_name()) || member.has_factory)) {
     if (member.has_factory) {
+      // TODO(regis): Simplify this code once the core library is fixed.
+      // See issue 6641.
+      // Per specification, the name of the factory must be the name of the
+      // immediately enclosing class.
+
       // The factory name may be qualified.
       QualIdent factory_name;
       ParseQualIdent(&factory_name);