Use entities in impact transformers.

pkg/compiler/lib/src/kernel/world_builder.dart

Index: pkg/compiler/lib/src/kernel/world_builder.dart
diff --git a/pkg/compiler/lib/src/kernel/world_builder.dart b/pkg/compiler/lib/src/kernel/world_builder.dart
index e86e06ce95e45eecf86dec77c4be544c34446e8c..37356f9a0c66b68cc61e10b32f1be14f2c483ce6 100644
--- a/pkg/compiler/lib/src/kernel/world_builder.dart
+++ b/pkg/compiler/lib/src/kernel/world_builder.dart
@@ -581,6 +581,15 @@ class KernelElementEnvironment implements ElementEnvironment {
   }
 
   @override
+  FunctionType getLocalFunctionType(Local function) {
+    throw new UnimplementedError(
+        'KernelElementEnvironment.getLocalFunctionType');
+  }
+
+  @override
+  DartType getUnaliasedType(DartType type) => type;
+
+  @override
   ConstructorEntity lookupConstructor(ClassEntity cls, String name,
       {bool required: false}) {
     ConstructorEntity constructor = worldBuilder.lookupConstructor(cls, name);