Fix for updating HINTS during incremental resolution with TM.

pkg/analyzer/test/generated/incremental_resolver_test.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 engine.incremental_resolver_test;
 
 import 'package:analyzer/src/context/cache.dart' as task;
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ skipping 3417 matching lines @@
 }
 ''');
     _updateAndValidate(r'''
 class A {
   void foo() {}
   void foo2() {}
 }
 ''');
   }
 
+  @override
   void setUp() {
+    AnalysisEngine.instance.useTaskModel = true;
     super.setUp();
     _resetWithIncremental(true);
   }
 
+  @override
+  void tearDown() {
+    super.tearDown();
+    AnalysisEngine.instance.useTaskModel = false;
+  }
+
   void test_computeConstants() {
     _resolveUnit(r'''
 int f() => 0;
 main() {
   const x = f();
   print(x + 1);
 }
 ''');
     _updateAndValidate(r'''
 int f() => 0;
@@ skipping 700 matching lines @@
 ''');
     _updateAndValidate(r'''
 class A {
   main(int b) {
     print(b);
   }
 }
 ''');
   }
 
+  void test_true_todoHint() {
+    _resolveUnit(r'''
+main() {
+  print(1);
+}
+foo() {
+ // TODO
+}
+''');
+    List<AnalysisError> oldErrors = analysisContext.computeErrors(source);
+    _updateAndValidate(r'''
+main() {
+  print(2);
+}
+foo() {
+ // TODO
+}
+''');
+    List<AnalysisError> newErrors = analysisContext.computeErrors(source);
+    _assertEqualErrors(newErrors, oldErrors);
+  }
+
   void test_unusedHint_add_wasUsedOnlyInPart() {
     Source partSource = addNamedSource(
         '/my_unit.dart',
         r'''
 part of lib;
 
 f(A a) {
   a._foo();
 }
 ''');
@@ skipping 569 matching lines @@
     return ResolutionContextBuilder.contextFor(node, listener).scope;
   }
 }
 
 class _Edit {
   final int offset;
   final int length;
   final String replacement;
   _Edit(this.offset, this.length, this.replacement);
 }