Create synthetic FieldElement(s) (don't use non-synthetic ones) for non-synthetic class getters/set…

pkg/analyzer/lib/src/task/incremental_element_builder.dart

 // Copyright (c) 2015, 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 analyzer.src.task.incremental_element_builder;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 196 matching lines @@
       oldElement.nameOffset = newElement.nameOffset;
       oldElement.setCodeRange(newElement.codeOffset, newElement.codeLength);
       oldElement.typeParameters = newElement.typeParameters;
     }
     // Prepare delta.
     ClassElementImpl classElement = oldClass.element;
     ElementHolder classElementHolder = new ElementHolder();
     ClassElementDelta classDelta =
         new ClassElementDelta(classElement, librarySource, classElement.name);
     // Prepare all old member elements.
-    var removedAccessors = new Set<PropertyAccessorElement>();
-    var removedConstructors = new Set<ConstructorElement>();
-    var removedMethods = new Set<MethodElement>();
+    var removedAccessors = new Set<PropertyAccessorElement>.identity();
+    var removedConstructors = new Set<ConstructorElement>.identity();
+    var removedMethods = new Set<MethodElement>.identity();
     removedAccessors.addAll(classElement.accessors);
     removedConstructors.addAll(classElement.constructors);
     removedMethods.addAll(classElement.methods);
     // Utilities.
     void processConstructorDeclaration(
         ConstructorDeclaration node, bool isNew) {
       ConstructorElement element = node.element;
       if (element != null) {
         classElementHolder.addConstructor(element);
         if (isNew) {
@@ skipping 515 matching lines @@
             } else if (element is ParameterElementImpl) {
               element.setVisibleRange(newOffset, newLength);
             }
           }
         }
       }
     }
     super.visitElement(element);
   }
 }