improve parser recovery when top level function is missing parameters

pkg/analysis_server/test/services/completion/local_computer_test.dart

 // Copyright (c) 2014, 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.
 
 library test.services.completion.dart.local;
 
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
 import 'package:analysis_server/src/services/completion/local_computer.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 131 matching lines @@
 ''');
     expect(computeFast(), isTrue);
     assertSuggestMethod('m', 'M2', 'void');
   }
 
   @override
   void setUpComputer() {
     computer = new LocalComputer();
   }
 
+  test_missing_params_function() {
+    addTestSource('int f1{} main(){f^}');
+    expect(computeFast(), isTrue);
+  }
+
+  test_missing_params_method() {
+    addTestSource('class C1{int f1{} main(){f^}}');
+    expect(computeFast(), isTrue);
+  }
+
+  test_missing_params_constructor() {
+    addTestSource('class C1{C1{} main(){C^}}');
+    expect(computeFast(), isTrue);
+  }
+
   test_break_ignores_outer_functions_using_closure() {
     addTestSource('''
 void main() {
   foo: while (true) {
     var f = () {
       bar: while (true) { break ^ }
     };
   }
 }
 ''');
@@ skipping 587 matching lines @@
     expect(computeFast(), isTrue);
     assertSuggestMethod('m', 'B', null, relevance: DART_RELEVANCE_LOCAL_METHOD);
   }
 
   test_shadowed_name() {
     addTestSource('var a; class A { var a; m() { ^ } }');
     expect(computeFast(), isTrue);
     assertSuggestLocalField('a', null);
   }
 }