fix NSM when computing field formal parameter in non-constructor arg list

pkg/analysis_server/test/services/completion/completion_test_util.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.util;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart' as protocol
     show Element, ElementKind;
@@ skipping 2007 matching lines @@
     addSource('/testA.dart', 'class A { }');
     addTestSource('''
       import "/testA.dart";
       class C {var ^}''');
     computeFast();
     return computeFull((bool result) {
       assertNoSuggestions();
     });
   }
 
+  test_FieldFormalParameter_in_non_constructor() {
+    // SimpleIdentifer  FieldFormalParameter  FormalParameterList
+    addTestSource('class A {B(this.^foo) {}}');
+    return computeFull((bool result) {
+      expect(request.replacementOffset, completionOffset);
+      expect(request.replacementLength, 3);
+      assertNoSuggestions();
+    });
+  }
+
   test_ForEachStatement_body_typed() {
     // Block  ForEachStatement
     addTestSource('main(args) {for (int foo in bar) {^}}');
     computeFast();
     return computeFull((bool result) {
       expect(request.replacementOffset, completionOffset);
       expect(request.replacementLength, 0);
       assertSuggestParameter('args', null);
       assertSuggestLocalVariable('foo', 'int');
       assertSuggestImportedClass('Object');
@@ skipping 1897 matching lines @@
       assertNotSuggested('bar2');
       assertNotSuggested('_B');
       assertSuggestLocalClass('Y');
       assertSuggestLocalClass('C');
       assertSuggestLocalVariable('f', null);
       assertNotSuggested('x');
       assertNotSuggested('e');
     });
   }
 }