Issue 22188. Verify that none or all execution flows return.

pkg/analyzer/lib/src/generated/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 engine.resolver;
 
 import "dart:math" as math;
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/utilities_collection.dart';
@@ skipping 4313 matching lines @@
 
   bool
       _visitVariableDeclarations(NodeList<VariableDeclaration> variableDeclarations) {
     for (int i = variableDeclarations.length - 1; i >= 0; i--) {
       if (variableDeclarations[i].accept(this)) {
         return true;
       }
     }
     return false;
   }
+
+  /**
+   * Return `true` if the given [node] exits.
+   */
+  static bool exits(AstNode node) {
+    return new ExitDetector()._nodeExits(node);
+  }
 }
 
 /**
  * Instances of the class `FunctionScope` implement the scope defined by a function.
  */
 class FunctionScope extends EnclosedScope {
   final ExecutableElement _functionElement;
 
   bool _parametersDefined = false;
 
@@ skipping 11343 matching lines @@
    * library.
    */
   final HashSet<String> members = new HashSet<String>();
 
   /**
    * Names of resolved or unresolved class members that are read in the
    * library.
    */
   final HashSet<String> readMembers = new HashSet<String>();
 }