Issue 25504. Fix for ignoring expression bodies in incremental resolver.

pkg/analyzer/lib/src/generated/incremental_resolver.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 analyzer.src.generated.incremental_resolver;
 
 import 'dart:collection';
 import 'dart:math' as math;
 
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 1475 matching lines @@
                 oldParent is ConstructorDeclaration &&
                     newParent is ConstructorDeclaration) {
               Element oldElement = (oldParent as Declaration).element;
               if (new DeclarationMatcher().matches(newParent, oldElement) ==
                   DeclarationMatchKind.MATCH) {
                 oldNode = oldParent;
                 newNode = newParent;
                 found = true;
               }
             }
-            if (oldParent is BlockFunctionBody &&
-                newParent is BlockFunctionBody) {
-              oldNode = oldParent;
-              newNode = newParent;
-              found = true;
-              break;
+            if (oldParent is FunctionBody || newParent is FunctionBody) {
+              if (oldParent is BlockFunctionBody &&
+                  newParent is BlockFunctionBody) {
+                oldNode = oldParent;
+                newNode = newParent;
+                found = true;
+                break;
+              }
+              logger.log('Failure: not a block function body.');
+              return false;
             }
           }
           if (!found) {
             logger.log('Failure: no enclosing function body or executable.');
             return false;
           }
           // fail if a comment change outside the bodies
           if (firstPair.kind == _TokenDifferenceKind.COMMENT) {
             if (beginOffsetOld <= oldNode.offset ||
                 beginOffsetNew <= newNode.offset) {
@@ skipping 593 matching lines @@
   @override
   String toString() => name;
 }
 
 class _TokenPair {
   final _TokenDifferenceKind kind;
   final Token oldToken;
   final Token newToken;
   _TokenPair(this.kind, this.oldToken, this.newToken);
 }