Issue 23568. Fix for NPE in index when unresolved field formal parameter.

pkg/analysis_server/lib/src/services/index/index_contributor.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 services.src.index.index_contributor;
 
 import 'dart:collection' show Queue;
 
 import 'package:analysis_server/analysis/index/index_core.dart';
 import 'package:analysis_server/analysis/index/index_dart.dart';
@@ skipping 424 matching lines @@
     } else {
       int start = node.thisKeyword.end;
       location = _createLocationForOffset(start, 0);
     }
     recordRelationship(element, IndexConstants.IS_REFERENCED_BY, location);
     super.visitRedirectingConstructorInvocation(node);
   }
 
   @override
   visitSimpleIdentifier(SimpleIdentifier node) {
-    IndexableObject indexable =
-        new IndexableElement(new NameElement(node.name));
+    Element nameElement = new NameElement(node.name);

[Brian Wilkerson, 2015/06/01 21:52:20]

I understand why lines 484-485 need to change, but is the change on this line
necessary to fix the bug? I explicitly didn't change this code so that we didn't
have to create one new instance of IndexableElement every time we recorded a
relationship about the name.

[scheglov, 2015/06/01 22:07:24]

We use "nameElement" only once, in different branches below, so we create only
one IndexableObject instance.

     LocationImpl location = _createLocationForNode(node);
     if (location == null) {
       return;
     }
     // name in declaration
     if (node.inDeclarationContext()) {
-      _store.recordRelationship(
-          indexable, IndexConstants.NAME_IS_DEFINED_BY, location);
+      recordRelationship(
+          nameElement, IndexConstants.NAME_IS_DEFINED_BY, location);
       return;
     }
     // prepare information
     Element element = node.bestElement;
     // stop if already handled
     if (_isAlreadyHandledName(node)) {
       return;
     }
     // record name read/write
     if (element != null && element.enclosingElement is ClassElement ||
         element == null && location.isQualified) {
       bool inGetterContext = node.inGetterContext();
       bool inSetterContext = node.inSetterContext();
       if (inGetterContext && inSetterContext) {
-        _store.recordRelationship(
-            indexable, IndexConstants.IS_READ_WRITTEN_BY, location);
+        recordRelationship(
+            nameElement, IndexConstants.IS_READ_WRITTEN_BY, location);
       } else if (inGetterContext) {
-        _store.recordRelationship(
-            indexable, IndexConstants.IS_READ_BY, location);
+        recordRelationship(nameElement, IndexConstants.IS_READ_BY, location);
       } else if (inSetterContext) {
-        _store.recordRelationship(
-            indexable, IndexConstants.IS_WRITTEN_BY, location);
+        recordRelationship(nameElement, IndexConstants.IS_WRITTEN_BY, location);
       }
     }
     // this.field parameter
     if (element is FieldFormalParameterElement) {
       RelationshipImpl relationship = peekElement().element == element
           ? IndexConstants.IS_WRITTEN_BY
           : IndexConstants.IS_REFERENCED_BY;
-      _store.recordRelationship(
-          new IndexableElement(element.field), relationship, location);
+      recordRelationship(element.field, relationship, location);
       return;
     }
     // record specific relations
     if (element is ClassElement ||
         element is FunctionElement ||
         element is FunctionTypeAliasElement ||
         element is LabelElement ||
         element is MethodElement ||
         element is PropertyAccessorElement ||
         element is PropertyInducingElement ||
@@ skipping 302 matching lines @@
   }
 
   /**
    * @return `true` if given "node" is part of [PrefixedIdentifier] "prefix.node".
    */
   static bool _isIdentifierInPrefixedIdentifier(SimpleIdentifier node) {
     AstNode parent = node.parent;
     return parent is PrefixedIdentifier && parent.identifier == node;
   }
 }