Fix bad type-inferrence for logical expressions.

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

Index: sdk/lib/_internal/compiler/implementation/inferrer/inferrer_visitor.dart
diff --git a/sdk/lib/_internal/compiler/implementation/inferrer/inferrer_visitor.dart b/sdk/lib/_internal/compiler/implementation/inferrer/inferrer_visitor.dart
index 86662f7dcb798a5ba86b62cd839375bd13f04499..12cbf777e445c1e2e341e1b0e70fbe74d2cf1720 100644
--- a/sdk/lib/_internal/compiler/implementation/inferrer/inferrer_visitor.dart
+++ b/sdk/lib/_internal/compiler/implementation/inferrer/inferrer_visitor.dart
@@ -842,6 +842,7 @@ abstract class InferrerVisitor
     } else if ("&&" == op.source) {
       conditionIsSimple = false;
       bool oldAccumulateIsChecks = accumulateIsChecks;
+      assert(accumulateIsChecks || isChecks == null);
       accumulateIsChecks = true;
       if (isChecks == null) isChecks = <Send>[];
       visit(node.receiver);
@@ -863,6 +864,7 @@ abstract class InferrerVisitor
       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);