Add strong mode type checking pass.

test/typecheck.dart

+// Copyright (c) 2016, 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.
+import 'package:kernel/kernel.dart';
+import 'package:kernel/class_hierarchy.dart';
+import 'package:kernel/core_types.dart';
+import 'package:kernel/type_checker.dart';
+import 'dart:io';
+
+final String usage = '''
+Usage: typecheck FILE.dill
+
+Runs the strong mode type checker on the given program.
+''';
+
+main(List<String> args) {
+  if (args.length != 1) {
+    print(usage);
+    exit(1);
+  }
+  var program = loadProgramFromBinary(args[0]);
+  var coreTypes = new CoreTypes(program);
+  var hierarchy = new ClassHierarchy(program);
+  new TestTypeChecker(coreTypes, hierarchy).checkProgram(program);
+}
+
+class TestTypeChecker extends TypeChecker {
+  TestTypeChecker(CoreTypes coreTypes, ClassHierarchy hierarchy)
+      : super(coreTypes, hierarchy);
+
+  @override
+  void checkAssignable(TreeNode where, DartType from, DartType to) {
+    if (!environment.isSubtypeOf(from, to)) {
+      fail(where, '$from is not a subtype of $to');
+    }
+  }
+
+  @override
+  void fail(TreeNode where, String message) {
+    Location location = where.location;
+    String locationString = location == null ? '' : '($location)';
+    print('[error] $message $locationString');
+  }
+}