Better toString and Error.toSafeString output for closures for dart2js.

tests/compiler/dart2js_extra/useful_error_message_1_test.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.
+
+// Test that closures have a useful string that identifies the function by name
+// in error messages.
+
+import "package:expect/expect.dart";
+
+@NoInline
+@AssumeDynamic
+confuse(x) => x;
+
+class CCCC {
+  instanceMethod([a, b]) => '[$a, $b]';
+  static staticMethod() => 'hi';
+  // Default `toString` method returns "Instance of 'CCCC'" or similar with a
+  // shorter name if minified.
+}
+
+main() {
+  var c = confuse(new CCCC());
+
+  var instanceString = confuse(c).toString();
+  bool isMinified = instanceString.contains(new RegExp("Instance of '..?.?'"));
+  if (!isMinified) {
+    Expect.equals("Instance of 'CCCC'", instanceString);
+  }
+
+  checkContains(String message, String tag) {
+    if (!message.contains(tag)) {
+      if (!isMinified) {
+        Expect.fail('"$message" should contain "$tag"');
+      }
+      // When minified we will accept quoted names up to 3 characters.
+      Expect.isTrue(
+          message.contains(new RegExp("'..?.?'")),
+          '"$message" should contain minified name');
+    }
+  }
+
+  // We use ArgumentError.value since it prints the value using
+  // Error.safeToString.
+  var e1 = new ArgumentError.value(c);
+  var s1 = '$e1';
+  Expect.isTrue(s1.contains(instanceString),
+      'Error message "$s1" should contain "$instanceString"');
+
+  // Instance method tear-off.
+  var e2 = new ArgumentError.value(confuse(c).instanceMethod);
+  var s2 = '$e2';
+  // Instance method tear-off should contain instance string.
+  Expect.isTrue(s2.contains(instanceString),
+      'Error message "$s2" should contain "$instanceString"');
+  // Instance method tear-off should also name the method.
+  checkContains(s2.replaceAll(instanceString, '*'), "instanceMethod");
+
+  // Top level tear-off.
+  var e3 = new ArgumentError.value(confuse);
+  var s3 = '$e3';
+  checkContains(s3, "confuse");
+  checkContains('$confuse', "confuse");
+
+  // Static method tear-off.
+  var e4 = new ArgumentError.value(CCCC.staticMethod);
+  var s4 = '$e4';
+  checkContains(s4, "staticMethod");
+  checkContains('${CCCC.staticMethod}', "staticMethod");
+
+  // Local anonymous closure.
+  var anon = () => c;
+  var e5 = new ArgumentError.value(anon);
+  var s5 = '$e5';
+  checkContains(s5, "main_closure");
+  checkContains('$anon', "main_closure");
+
+  // Local named closure.
+  localFunction() => c;
+  var e6 = new ArgumentError.value(localFunction);
+  var s6 = '$e6';
+  checkContains(s6, "localFunction");
+  checkContains('$localFunction', "localFunction");
+}