Fix instances where a loop 'always' exits, but also breaks, so it doesn't really exit.

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 3538 matching lines @@
   }
 
   @override
   bool visitContinueStatement(ContinueStatement node) => false;
 
   @override
   bool visitDoStatement(DoStatement node) {
     bool outerBreakValue = _enclosingBlockContainsBreak;
     _enclosingBlockContainsBreak = false;
     try {
-      if (_nodeExits(node.body)) {
+      if (_nodeExits(node.body) && !_enclosingBlockContainsBreak) {
         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) {
@@ skipping 281 matching lines @@
 
   @override
   bool visitWhileStatement(WhileStatement node) {
     bool outerBreakValue = _enclosingBlockContainsBreak;
     _enclosingBlockContainsBreak = false;
     try {
       Expression conditionExpression = node.condition;
       if (conditionExpression.accept(this)) {
         return true;
       }
-      bool blockReturns = node.body.accept(this);
+      node.body.accept(this);
       // TODO(jwren) Do we want to take all constant expressions into account?
       if (conditionExpression is BooleanLiteral) {
-        // If while(true), and the body doesn't return or the body doesn't have
-        // a break, then return true.
-        if (conditionExpression.value &&
-            (blockReturns || !_enclosingBlockContainsBreak)) {
+        // If while(true), and the body doesn't have a break, then return true.
+        // The body might be found to exit, but if there are any break
+        // statements, then it is a faulty finding. In other words:
+        //
+        // * If the body exits, and does not contain a break statement, then
+        //   it exits.
+        // * If the body does not exit, and does not contain a break statement,
+        //   then it loops infinitely (also an exit).
+        //
+        // As both conditions forbid any break statements to be found, the logic
+        // just boils down to checking [_enclosingBlockContainsBreak].
+        if (conditionExpression.value && !_enclosingBlockContainsBreak) {
           return true;
         }
       }
       return false;
     } finally {
       _enclosingBlockContainsBreak = outerBreakValue;
     }
   }
 
   @override
@@ skipping 7080 matching lines @@
       return null;
     }
     if (identical(node.staticElement, variable)) {
       if (node.inSetterContext()) {
         result = true;
       }
     }
     return null;
   }
 }