Add a test and improve comment on generic checks.

sdk/lib/_internal/compiler/implementation/ssa/optimize.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of ssa;
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
@@ skipping 523 matching lines @@
       } else {
         return graph.addConstantBool(false, constantSystem);
       }
     } else if (expressionType.isArray()) {
       if (identical(element, compiler.listClass)
           || Elements.isListSupertype(element, compiler)) {
         return graph.addConstantBool(true, constantSystem);
       } else {
         return graph.addConstantBool(false, constantSystem);
       }
-    // TODO(karlklose): remove the hasTypeArguments check.
+    // Wee need the [:hasTypeArguments:] check because we don't have
+    // the notion of generics in the backend. For example, [:this:] in
+    // a class [:A<T>:], is currently always considered to have the
+    // raw type.
     } else if (expressionType.isUseful()
                && !expressionType.canBeNull()
                && !RuntimeTypeInformation.hasTypeArguments(type)) {
       DartType receiverType = expressionType.computeType(compiler);
       if (receiverType != null) {
         if (!receiverType.isMalformed &&
             !type.isMalformed &&
-            compiler.types.isSubtype(receiverType, type)) {
+            compiler.types.isSubtype(receiverType.element.rawType, type)) {
           return graph.addConstantBool(true, constantSystem);
         } else if (expressionType.isExact()) {
           return graph.addConstantBool(false, constantSystem);
         }
       }
     }
     return node;
   }
 
   HInstruction visitTypeConversion(HTypeConversion node) {
@@ skipping 980 matching lines @@
     HBasicBlock block = user.block;
     block.addAfter(user, interceptor);
     block.rewrite(user, interceptor);
     block.remove(user);
 
     // The interceptor will be removed in the dead code elimination
     // phase. Note that removing it here would not work because of how
     // the [visitBasicBlock] is implemented.
   }
 }