Throw TypeError instead of CastError for type coercions.

tool/input_sdk/private/ddc_runtime/utils.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.
 part of dart._runtime;
 
 /// This library defines a set of general javascript utilities for us
 /// by the Dart runtime.
 // TODO(ochafik): Rewrite some of these in Dart when possible.
 
 defineProperty(obj, name, desc) =>
     JS('', 'Object.defineProperty(#, #, #)', obj, name, desc);
 
 getOwnPropertyDescriptor(obj, name) =>
     JS('', 'Object.getOwnPropertyDescriptor(#, #)', obj, name);
 
 Iterable getOwnPropertyNames(obj) =>
     JS('', 'Object.getOwnPropertyNames(#)', obj);
 
 Iterable getOwnPropertySymbols(obj) =>
     JS('', 'Object.getOwnPropertySymbols(#)', obj);
 
 final hasOwnProperty = JS('', 'Object.prototype.hasOwnProperty');
 
-// TODO(ochafik): Add ES6 class syntax support to JS intrinsics to avoid this.
-final StrongModeError = JS('', '''(function() {
-  function StrongModeError(message) {
-    Error.call(this);
-    this.message = message;
-  };
-  Object.setPrototypeOf(StrongModeError.prototype, Error.prototype);
-  return StrongModeError;
-})()''');
-
-/// This error indicates a strong mode specific failure.
+/// This error indicates a strong mode specific failure, other than a type
+/// assertion failure (TypeError) or CastError.
 void throwStrongModeError(String message) {
-  JS('', 'throw new #(#);', StrongModeError, message);
+  JS('', 'throw new #(#);', StrongModeErrorImplementation, message);
 }
 
 /// This error indicates a bug in the runtime or the compiler.
 void throwInternalError(String message) {
   JS('', 'throw Error(#)', message);
 }
 
 getOwnNamesAndSymbols(obj) {
   var names = getOwnPropertyNames(obj);
   var symbols = getOwnPropertySymbols(obj);
@@ skipping 71 matching lines @@
 }
 
 @JSExportName('export')
 exportProperty(to, from, name) => copyProperty(to, from, name);
 
 /// Copy properties from source to destination object.
 /// This operation is commonly called `mixin` in JS.
 copyProperties(to, from) {
   return copyTheseProperties(to, from, getOwnNamesAndSymbols(from));
 }