fix analysis messages

lib/runtime/dart_runtime.dart

 // Copyright (c) 2015, 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.
 
 library ddc.runtime.dart_runtime;
 
 import 'dart:mirrors';
 
 import 'package:dev_compiler/config.dart';
 
@@ skipping 110 matching lines @@
       // Ignore named parameters - these cannot be passed positionally.
     } else if (parameter.isOptional) {
       optionalPositional++;
     } else {
       normal++;
     }
   }
   return new Arity._internal(normal, optionalPositional);
 }
 
-bool _isFunctionSubType(TypeMirror t1, TypeMirror t2) {
-  // Function types follow the standard non-Dart rule:
-  // - contravariant on param types
-  // - covariant on return type
-  final f1 = t1 as FunctionTypeMirror;
-  final f2 = t2 as FunctionTypeMirror;
-
-  final params1 = f1.parameters;
-  final params2 = f2.parameters;
-  final ret1 = f1.returnType;
-  final ret2 = f2.returnType;
-  return _isFunctionSubTypeHelper(ret1, params1, ret2, params2);
-}
-
-bool _isFunctionSubTypeHelper(TypeMirror ret1, List<ParameterMirror> params1,
+bool _isFunctionSubType(TypeMirror ret1, List<ParameterMirror> params1,
     TypeMirror ret2, List<ParameterMirror> params2) {
   if (!_isSubType(ret1, ret2)) {
     // Covariant return types
     // Note, void (which can only appear as a return type) is effectively
     // treated as dynamic.  If the base return type is void, we allow any
     // subtype return type.
     // E.g., we allow:
     //   () -> int <: () -> void
     if (ret2.simpleName != const Symbol('void')) {
       return false;
@@ skipping 171 matching lines @@
     if (call1 == null || !call1.isRegularMethod) return false;
     // Class that emulate a function
     ret1 = call1.returnType;
     params1 = call1.parameters;
   }
 
   // Any type that implements a call method implicitly subtypes Function.
   if (_reflects(c2, Function)) return true;
 
   // Check structural function subtyping
-  return _isFunctionSubTypeHelper(ret1, params1, c2.returnType, c2.parameters);
+  return _isFunctionSubType(ret1, params1, c2.returnType, c2.parameters);
 }