Consider updates of locals in type promotion.

pkg/compiler/lib/src/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 132 matching lines @@
 
   VariableScope.deepCopyOf(VariableScope<T> other)
       : variables = other.variables == null
             ? null
             : new Map<Local, T>.from(other.variables),
         block = other.block,
         parent = other.parent == null
             ? null
             : new VariableScope<T>.deepCopyOf(other.parent);
 
+  VariableScope.topLevelCopyOf(VariableScope<T> other)
+      : variables = other.variables == null
+            ? null
+            : new Map<Local, T>.from(other.variables),
+        block = other.block,
+        parent = other.parent;
+
   T operator [](Local variable) {
     T result;
     if (variables == null || (result = variables[variable]) == null) {
       return parent == null ? null : parent[variable];
     }
     return result;
   }
 
   void operator []=(Local variable, T mask) {
     assert(mask != null);
@@ skipping 231 matching lines @@
   LocalsHandler.deepCopyOf(LocalsHandler<T> other)
       : locals = new VariableScope<T>.deepCopyOf(other.locals),
         fieldScope = new FieldInitializationScope<T>.from(other.fieldScope),
         captured = other.captured,
         capturedAndBoxed = other.capturedAndBoxed,
         tryBlock = other.tryBlock,
         types = other.types,
         inferrer = other.inferrer,
         compiler = other.compiler;
 
+  LocalsHandler.topLevelCopyOf(LocalsHandler<T> other)
+      : locals = new VariableScope<T>.topLevelCopyOf(other.locals),
+        fieldScope = new FieldInitializationScope<T>.from(other.fieldScope),
+        captured = other.captured,
+        capturedAndBoxed = other.capturedAndBoxed,
+        tryBlock = other.tryBlock,
+        types = other.types,
+        inferrer = other.inferrer,
+        compiler = other.compiler;
+
   T use(Local local) {
     if (capturedAndBoxed.containsKey(local)) {
       return inferrer.typeOfElement(capturedAndBoxed[local]);
     } else {
       if (captured.containsKey(local)) {
         inferrer.recordCapturedLocalRead(local);
       }
       return locals[local];
     }
   }
@@ skipping 485 matching lines @@
       bool oldAccumulateIsChecks = accumulateIsChecks;
       List<Send> oldIsChecks = isChecks;
       if (!accumulateIsChecks) {
         accumulateIsChecks = true;
         isChecks = <Send>[];
       }
       visit(node.receiver);
       LocalsHandler<T> saved = locals;
       locals = new LocalsHandler<T>.from(locals, node);
       updateIsChecks(isChecks, usePositive: true);
-      if (!oldAccumulateIsChecks) {
+      LocalsHandler<T> narrowed;
+      if (oldAccumulateIsChecks) {
+        narrowed = new LocalsHandler<T>.topLevelCopyOf(locals);
+      } else {
         accumulateIsChecks = false;
         isChecks = oldIsChecks;
       }
       visit(node.arguments.head);
+      if (oldAccumulateIsChecks) {
+
+        bool invalidatedInRightHandSide (Send test) {
+          Element receiver = elements[test.receiver];
+          if (receiver is LocalElement) {
+            return narrowed.locals[receiver] != locals.locals[receiver];
+          }
+          return false;
+        }
+
+        isChecks.removeWhere(invalidatedInRightHandSide);
+      }
       saved.mergeDiamondFlow(locals, null);
       locals = saved;
       return types.boolType;
     } else if ("||" == op.source) {
       conditionIsSimple = false;
       List<Send> tests = <Send>[];
       bool isSimple = handleCondition(node.receiver, tests);
       LocalsHandler<T> saved = locals;
       locals = new LocalsHandler<T>.from(locals, node);
       if (isSimple) updateIsChecks(tests, usePositive: false);
@@ skipping 345 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();
   }
 }