ExitDetector: Examine continue when determining a 'do'

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 analyzer.src.generated.resolver;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 3481 matching lines @@
  * expression, or simple infinite loop such as `while(true)`.
  */
 class ExitDetector extends GeneralizingAstVisitor<bool> {
   /**
    * Set to `true` when a `break` is encountered, and reset to `false` when a
    * `do`, `while`, `for` or `switch` block is entered.
    */
   bool _enclosingBlockContainsBreak = false;
 
   /**
+   * Set to `true` when a `continue` is encountered, and reset to `false` when a
+   * `do`, `while`, `for` or `switch` block is entered.
+   */
+  bool _enclosingBlockContainsContinue = false;
+
+  /**
    * Add node when a labelled `break` is encountered.
    */
   Set<AstNode> _enclosingBlockBreaksLabel = new Set<AstNode>();
 
   @override
   bool visitArgumentList(ArgumentList node) =>
       _visitExpressions(node.arguments);
 
   @override
   bool visitAsExpression(AsExpression node) => _nodeExits(node.expression);
@@ skipping 87 matching lines @@
     if (_nodeExits(conditionExpression)) {
       return true;
     }
     if (thenStatement == null || elseStatement == null) {
       return false;
     }
     return thenStatement.accept(this) && elseStatement.accept(this);
   }
 
   @override
-  bool visitContinueStatement(ContinueStatement node) => false;
+  bool visitContinueStatement(ContinueStatement node) {
+    _enclosingBlockContainsContinue = true;
+    return false;
+  }
 
   @override
   bool visitDoStatement(DoStatement node) {
     bool outerBreakValue = _enclosingBlockContainsBreak;
+    bool outerContinueValue = _enclosingBlockContainsContinue;
     _enclosingBlockContainsBreak = false;
+    _enclosingBlockContainsContinue = false;
     try {
-      if (_nodeExits(node.body) && !_enclosingBlockContainsBreak) {
+      bool bodyExits = _nodeExits(node.body);
+      bool containsBreakOrContinue =
+          _enclosingBlockContainsBreak || _enclosingBlockContainsContinue;
+      // Even if we determine that the body "exits", there might be break or
+      // continue statements that actually mean it _doesn't_ always exit.
+      if (bodyExits && !containsBreakOrContinue) {
         return true;
       }
       Expression conditionExpression = node.condition;
       if (_nodeExits(conditionExpression)) {
         return true;
       }
       // TODO(jwren) Do we want to take all constant expressions into account?
       if (conditionExpression is BooleanLiteral) {
         // If do {} while (true), and the body doesn't break, then return true.
         if (conditionExpression.value && !_enclosingBlockContainsBreak) {
           return true;
         }
       }
       return false;
     } finally {
       _enclosingBlockContainsBreak = outerBreakValue;
+      _enclosingBlockContainsContinue = outerContinueValue;
     }
   }
 
   @override
   bool visitEmptyStatement(EmptyStatement node) => false;
 
   @override
   bool visitExpressionStatement(ExpressionStatement node) =>
       _nodeExits(node.expression);
 
@@ skipping 7397 matching lines @@
       return null;
     }
     if (identical(node.staticElement, variable)) {
       if (node.inSetterContext()) {
         result = true;
       }
     }
     return null;
   }
 }