Improve type test and type equality for generics (issue 15148).

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
===================================================================
--- runtime/vm/flow_graph_compiler.cc	(revision 30544)
+++ runtime/vm/flow_graph_compiler.cc	(working copy)
@@ -1188,13 +1188,16 @@
   if (type_class.is_implemented()) return false;
   const intptr_t type_cid = type_class.id();
   if (CHA::HasSubclasses(type_cid)) return false;
-  if (type_class.NumTypeArguments() > 0) {
+  const intptr_t num_type_args = type_class.NumTypeArguments();
+  if (num_type_args > 0) {
     // Only raw types can be directly compared, thus disregarding type
     // arguments.
+    const intptr_t num_type_params = type_class.NumTypeParameters();
+    const intptr_t from_index = num_type_args - num_type_params;
     const AbstractTypeArguments& type_arguments =
         AbstractTypeArguments::Handle(type.arguments());
     const bool is_raw_type = type_arguments.IsNull() ||
-        type_arguments.IsRaw(type_arguments.Length());
+        type_arguments.IsRaw(from_index, num_type_params);
     return is_raw_type;
   }
   return true;