Big merge from experimental to bleeding edge.

sdk/lib/async/async_error.dart

Index: sdk/lib/async/async_error.dart
diff --git a/sdk/lib/async/async_error.dart b/sdk/lib/async/async_error.dart
new file mode 100644
index 0000000000000000000000000000000000000000..aad80b7f8b5a2c818e954ca4c49cf75f45c3f0f6
--- /dev/null
+++ b/sdk/lib/async/async_error.dart
@@ -0,0 +1,74 @@
+// Copyright (c) 2012, 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.async;
+
+/**
+ * Error result of an asynchronous computation.
+ */
+class AsyncError {
+  /** The actual error thrown by the computation. */
+  final Object error;
+  /** Stack trace corresponding to the error, if available. */
+  final Object stackTrace;
+  /** Asynchronous error leading to this error, if error handling fails. */
+  final AsyncError cause;
+
+  // TODO(lrn): When possible, combine into one constructor with both optional
+  // positional and named arguments.
+  AsyncError(Object this.error, [Object this.stackTrace]): cause = null;
+  AsyncError.withCause(Object this.error, Object this.stackTrace, this.cause);
+
+  void _writeOn(StringBuffer buffer) {
+    buffer.add("'");
+    String message;
+    try {
+      message = error.toString();
+    } catch (e) {
+      message = Error.safeToString(error);
+    }
+    buffer.add(message);
+    buffer.add("'\n");
+    if (stackTrace != null) {
+      buffer.add("Stack trace:\n");
+      buffer.add(stackTrace.toString());
+      buffer.add("\n");
+    }
+  }
+
+  String toString() {
+    StringBuffer buffer = new StringBuffer();
+    buffer.add("AsyncError: ");
+    _writeOn(buffer);
+    AsyncError cause = this.cause;
+    while (cause != null) {
+      buffer.add("Caused by: ");
+      cause._writeOn(buffer);
+      cause = cause.cause;
+    }
+    return buffer.toString();
+  }
+
+  throwDelayed() {
+    reportError() {
+      print("Uncaught Error: $error");
+      if (stackTrace != null) {
+        print("Stack Trace:\n$stackTrace\n");
+      }
+    }
+
+    try {
+      new Timer(0, (_) {
+        reportError();
+        // TODO(floitsch): we potentially want to call the global error handler
+        // directly so that we can pass the stack trace.
+        throw error;
+      });
+    } catch (e) {
+      // Unfortunately there is not much more we can do...
+      reportError();
+    }
+  }
+}
+