- Allow parsing of external methods.

tests/language/external_test.dart

+// 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.
+
+class Foo {
+  var x;
+  f() {}
+
+  external var x01;  /// 01: compile-time error
+  external int x02;  /// 02: compile-time error
+
+  external f10();   /// 10: runtime error
+  external f11() { }  /// 11: compile-time error
+  external f12() => 1;  /// 12: compile-time error
+  external static f13();  /// 13: runtime error
+  static external f14();  /// 14: compile-time error
+  external abstract f15();  /// 15: compile-time error
+  int external f16();  /// 16: compile-time error
+
+  external Foo.n20();  /// 20: runtime error
+  external Foo.n21() : x(1);  /// 21: compile-time error
+  external Foo.n22() { x = 1; }  /// 22: compile-time error
+  external factory Foo.n23() => new Foo();  /// 23: compile-time error
+}
+
+external int t06(int i) { }  /// 30: compile-time error
+external int t07(int i) => i + 1;  /// 31: compile-time error
+
+main() {
+
+  // Try calling an unpatched external function.
+  var foo = new Foo();                                /// 10: continued
+  try {                                               /// 10: continued
+    foo.f05();                                        /// 10: continued
+  } catch (String exc) {                              /// 10: continued
+    if (exc == "External implementation missing.") {  /// 10: continued
+      throw exc;                                      /// 10: continued
+    }                                                 /// 10: continued
+  }                                                   /// 10: continued
+
+  try {                                               /// 13: continued
+    Foo.f13();                                        /// 13: continued
+  } catch (String exc) {                              /// 13: continued
+    if (exc == "External implementation missing.") {  /// 13: continued
+      throw exc;                                      /// 13: continued
+    }                                                 /// 13: continued
+  }                                                   /// 13: continued
+
+  // Try calling an unpatched external constructor.
+  try {                                               /// 20: continued
+    var foo = new Foo.n09();                          /// 20: continued
+  } catch (String exc) {                              /// 20: continued
+    if (exc == "External implementation missing.") {  /// 20: continued
+      throw exc;                                      /// 20: continued
+    }                                                 /// 20: continued
+  }                                                   /// 20: continued
+}