Add optional message to assert in Dart2js.

tests/compiler/dart2js/type_inference7_test.dart

Index: tests/compiler/dart2js/type_inference7_test.dart
diff --git a/tests/compiler/dart2js/type_inference7_test.dart b/tests/compiler/dart2js/type_inference7_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..5a3b5f5530de1a188500ee33033e338f46b26dbe
--- /dev/null
+++ b/tests/compiler/dart2js/type_inference7_test.dart
@@ -0,0 +1,81 @@
+// Copyright (c) 2011, 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:async_helper/async_helper.dart";
+import "package:expect/expect.dart";
+import 'compiler_helper.dart';
+import 'type_mask_test_helper.dart';
+
+import 'dart:async';
+
+const String TEST = r"""
+foo(x, [y]) => y;
+
+main() {
+  assert(foo("Hi", true), foo(true));
+  foo(1);
+}
+""";
+
+Future runTest() async {
+  Uri uri = new Uri(scheme: 'source');
+  {
+    // Checked mode:
+    var compiler = compilerFor(TEST, uri, enableTypeAssertions: true);
+    await compiler.runCompiler(uri);
+    var typesTask = compiler.typesTask;
+    var typesInferrer = typesTask.typesInferrer;
+    var element = findElement(compiler, "foo");
+    var parameters = element.parameters;
+    // Return type is null|bool.
+    var mask = typesInferrer.getReturnTypeOfElement(element);
+    Expect.isTrue(mask.isNullable);
+    Expect.equals(typesTask.boolType, simplify(mask.nonNullable(), compiler));
+    // First parameter is uint31|String|bool.
+    var mask1 = typesInferrer.getTypeOfElement(parameters[0]);
+    Expect.isTrue(mask1.isUnion);
+    var expectedTypes = new Set.from([typesTask.uint31Type,
+                                      typesTask.stringType,
+                                      typesTask.boolType]);
+    for (var typeMask in mask1.disjointMasks) {
+      Expect.isFalse(typeMask.isNullable);
+      var simpleType = simplify(typeMask, compiler);
+      Expect.isTrue(expectedTypes.remove(simpleType), "$simpleType");
+    }
+    Expect.isTrue(expectedTypes.isEmpty);
+    // Second parameter is bool or null.
+    var mask2 = typesInferrer.getTypeOfElement(parameters[1]);
+    Expect.isTrue(mask2.isNullable);
+    Expect.equals(typesTask.boolType, simplify(mask2.nonNullable(), compiler));
+  }
+  {
+    // Production mode:
+    var compiler = compilerFor(TEST, uri, enableTypeAssertions: false);
+    await compiler.runCompiler(uri);
+    var typesTask = compiler.typesTask;
+    var typesInferrer = typesTask.typesInferrer;
+    var element = findElement(compiler, "foo");
+    var parameters = element.parameters;
+    // Return type is null.
+    var mask = typesInferrer.getReturnTypeOfElement(element);
+    Expect.isTrue(mask.isNullable);
+    Expect.equals(typesTask.emptyType, simplify(mask.nonNullable(), compiler));
+    // First parameter is uint31.
+    var mask1 = typesInferrer.getTypeOfElement(parameters[0]);
+    Expect.isFalse(mask1.isNullable);
+    Expect.equals(typesTask.uint31Type, simplify(mask1, compiler));
+    // Second parameter is null.
+    var mask2 = typesInferrer.getTypeOfElement(parameters[1]);
+    Expect.isTrue(mask2.isNullable);
+    Expect.equals(typesTask.emptyType, simplify(mask2.nonNullable(), compiler));
+  }
+}
+
+main() {
+  asyncStart();
+  runTest().then((_) {
+    // Make sure that the type is still correct when we do a second compilation.
+    return runTest();
+  }).whenComplete(asyncEnd);
+}