Fix bad type-inferrence for logical expressions.

sdk/lib/_internal/compiler/implementation/inferrer/inferrer_visitor.dart

 // Copyright (c) 2013, 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 inferrer_visitor;
 
 import '../dart2jslib.dart' hide Selector, TypedSelector;
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../tree/tree.dart';
@@ skipping 824 matching lines @@
     }
   }
 
   T visitOperatorSend(Send node) {
     Operator op = node.selector;
     if ("[]" == op.source) {
       return visitDynamicSend(node);
     } else if ("&&" == op.source) {
       conditionIsSimple = false;
       bool oldAccumulateIsChecks = accumulateIsChecks;
+      assert(accumulateIsChecks || isChecks == null);
       accumulateIsChecks = true;
       if (isChecks == null) isChecks = <Send>[];
       visit(node.receiver);
       accumulateIsChecks = oldAccumulateIsChecks;
       if (!accumulateIsChecks) isChecks = null;
       LocalsHandler<T> saved = locals;
       locals = new LocalsHandler<T>.from(locals, node);
       updateIsChecks(isChecks, usePositive: true);
       visit(node.arguments.head);
       saved.mergeDiamondFlow(locals, null);
       locals = saved;
       return types.boolType;
     } else if ("||" == op.source) {
       conditionIsSimple = false;
       List<Send> tests = <Send>[];
       handleCondition(node.receiver, tests);
       LocalsHandler<T> saved = locals;
       locals = new LocalsHandler<T>.from(locals, node);
       updateIsChecks(tests, usePositive: false);
       bool oldAccumulateIsChecks = accumulateIsChecks;
       accumulateIsChecks = false;
+      isChecks = null;

[ngeoffray, 2014/02/27 10:33:12]

How about an abstraction:

bool stopAccumulatingIsChecks() {
  bool oldAccumulateIsChecks = accumulateIsChecks;
  accumulateIsChecks = false;
  isChecks = null;
  return oldAccumulateIsChecks.
}

And add a comment why.

[floitsch, 2014/02/27 16:07:08]

Added helper.

Changed the assert from the '&&' into code that sets the field always if the
oldAccumulateIsChecks was false. This avoids further errors.

       visit(node.arguments.head);
       accumulateIsChecks = oldAccumulateIsChecks;
       saved.mergeDiamondFlow(locals, null);
       locals = saved;
       return types.boolType;
     } else if ("!" == op.source) {
       bool oldAccumulateIsChecks = accumulateIsChecks;
       accumulateIsChecks = false;

[floitsch, 2014/02/27 16:07:08]

Similar bug. (fixed in latest patch-set).

       node.visitChildren(this);
       accumulateIsChecks = oldAccumulateIsChecks;
       return types.boolType;
     } else if ("is" == op.source) {
       potentiallyAddIsCheck(node);
       node.visitChildren(this);
       return types.boolType;
     } else if ("as" == op.source) {
       T receiverType = visit(node.receiver);
       DartType type = elements.getType(node.arguments.head);
@@ skipping 322 matching lines @@
     return type;
   }
 
   T visitCascade(Cascade node) {
     // Ignore the result of the cascade send and return the type of the cascade
     // receiver.
     visit(node.expression);
     return cascadeReceiverStack.removeLast();
   }
 }