Throw TypeError instead of CastError for type coercions.

tool/input_sdk/private/js_helper.dart

 // Copyright (c) 2013, 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 dart._js_helper;
 
 import 'dart:collection';
 
 import 'dart:_foreign_helper' show
     JS,
@@ skipping 764 matching lines @@
 // TODO(lrn): These exceptions should be implemented in core.
 // When they are, remove the 'Implementation' here.
 
 /** Thrown by type assertions that fail. */
 class TypeErrorImplementation extends Error implements TypeError {
   final String message;
 
   /**
    * Normal type error caused by a failed subtype test.
    */
-  TypeErrorImplementation(Object value, String type)
-      : message = "type '${Primitives.objectTypeName(value)}' is not a subtype "
-                  "of type '$type'";
+  TypeErrorImplementation(Object value, Object actualType, Object expectedType)
+      : message = "Type '${actualType}' is not a subtype "
+                  "of type '${expectedType}'";
 
   TypeErrorImplementation.fromMessage(String this.message);
 
   String toString() => message;
 }
 
 /** Thrown by the 'as' operator if the cast isn't valid. */
 class CastErrorImplementation extends Error implements CastError {
   // TODO(lrn): Rename to CastError (and move implementation into core).
   final String message;
 
   /**
    * Normal cast error caused by a failed type cast.
    */
-  CastErrorImplementation(Object actualType, Object expectedType)
-      : message = "CastError: Casting value of type $actualType to"
-                  " incompatible type $expectedType";
+  CastErrorImplementation(Object value, Object actualType, Object expectedType)

[Leaf, 2016/06/01 17:01:51]

Why the unused "value" parameter?

[sra1, 2016/06/01 17:07:13]

I will add a TODO, but I would eventually like the exception to display the
value as well as its type.

+      : message = "CastError: Casting value of type '$actualType' to"
+                  " incompatible type '$expectedType'";
 
   String toString() => message;
 }
 
+/// Thrown by type assertions that fail in strong mode that would have passed in
+/// standard Dart.
+class StrongModeTypeError extends Error implements TypeError, StrongModeError {
+  final String message;
+  StrongModeTypeError(Object value, Object actualType, Object expectedType)
+      : message = "Type '${actualType}' is not a subtype "
+                  "of type '${expectedType}' in strong mode";
+  String toString() => message;
+}
+
+/// Thrown by casts that fail in strong mode that would have passed in standard
+/// Dart.
+class StrongModeCastError extends Error implements CastError, StrongModeError {
+  final String message;
+  StrongModeCastError(Object value, Object actualType, Object expectedType)
+      : message = "CastError: Casting value of type '$actualType' to"
+                  " type '$expectedType' which is incompatible in strong mode";
+  String toString() => message;
+}
+
+/// Used for Strong-mode errors other than type assertions and casts.
+class StrongModeErrorImplementation extends Error implements StrongModeError {
+  final String message;
+  StrongModeErrorImplementation(this.message);
+  String toString() => message;
+}
+
 class FallThroughErrorImplementation extends FallThroughError {
   FallThroughErrorImplementation();
   String toString() => "Switch case fall-through.";
 }
 
 /**
  * Error thrown when a runtime error occurs.
  */
 class RuntimeError extends Error {
   final message;
@@ skipping 45 matching lines @@
   // we have no way of telling the compiler yet, so it will generate an extra
   // layer of indirection that wraps the SyncIterator.
   _jsIterator() => JS('', '#(...#)', _generator, _args);
 
   Iterator<E> get iterator => new SyncIterator<E>(_jsIterator());
 }
 
 class BooleanConversionAssertionError extends AssertionError {
   toString() => 'Failed assertion: boolean expression must not be null';
 }