Fix forEachOverridePair in the case where the class in question is abstract.

pkg/kernel/lib/src/incremental_class_hierarchy.dart

 // Copyright (c) 2017, 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 kernel.incremental_class_hierarchy;
 
 import 'dart:collection';
 import 'dart:math';
 
 import 'package:kernel/ast.dart';
 import 'package:kernel/class_hierarchy.dart';
@@ skipping 86 matching lines @@
 
       _reportOverrides(info.implementedGettersAndCalls, superGetters, callback);
       _reportOverrides(info.declaredGettersAndCalls, superGetters, callback,
           onlyAbstract: true);
 
       _reportOverrides(info.implementedSetters, superSetters, callback,
           isSetter: true);
       _reportOverrides(info.declaredSetters, superSetters, callback,
           isSetter: true, onlyAbstract: true);
     }
-    if (!node.isAbstract) {
-      // If a non-abstract class declares an abstract method M whose
-      // implementation M' is inherited from the superclass, then the inherited
-      // method M' overrides the declared method M.
-      // This flies in the face of conventional override logic, but is necessary
-      // because an instance of the class will contain the method M' which can
-      // be invoked through the interface of M.
-      // Note that [_reportOverrides] does not report self-overrides, so in
-      // most cases these calls will just scan both lists and report nothing.
-      _reportOverrides(info.implementedGettersAndCalls,
-          info.declaredGettersAndCalls, callback);
-      _reportOverrides(info.implementedSetters, info.declaredSetters, callback,
-          isSetter: true);
-    }
+    // If a class declares an abstract method M whose
+    // implementation M' is inherited from the superclass, then the inherited
+    // method M' overrides the declared method M.
+    // This flies in the face of conventional override logic, but is necessary
+    // because an instance of the class will contain the method M' which can
+    // be invoked through the interface of M.
+    // Note that [_reportOverrides] does not report self-overrides, so in
+    // most cases these calls will just scan both lists and report nothing.
+    _reportOverrides(info.implementedGettersAndCalls,
+        info.declaredGettersAndCalls, callback);
+    _reportOverrides(info.implementedSetters, info.declaredSetters, callback,
+        isSetter: true);
   }
 
   @override
   void forEachCrossOverridePair(Class node,
       callback(Member declaredMember, Member interfaceMember, bool isSetter),
       {bool crossGettersSetters: false}) {
     _ClassInfo info = _getInfo(node);
     for (var supertype in node.supers) {
       var superNode = supertype.classNode;
       var superInfo = _getInfo(superNode);
@@ skipping 612 matching lines @@
 class _LubHeap extends Heap<_ClassInfo> {
   @override
   bool sortsBefore(_ClassInfo a, _ClassInfo b) => sortsBeforeStatic(a, b);
 
   static bool sortsBeforeStatic(_ClassInfo a, _ClassInfo b) {
     if (a.depth > b.depth) return true;
     if (a.depth < b.depth) return false;
     return a.id < b.id;
   }
 }