Detect total switches to prevent type pollution by default cases.

sdk/lib/_internal/compiler/implementation/ssa/value_range_analyzer.dart

 // Copyright (c) 2012, 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.
 
 part of ssa;
 
 
 class ValueRangeInfo {
   final ConstantSystem constantSystem;
 
@@ skipping 592 matching lines @@
       : info = new ValueRangeInfo(constantSystem),
         this.constantSystem = constantSystem;
 
   void visitGraph(HGraph graph) {
     this.graph = graph;
     visitDominatorTree(graph);
     // We remove the range conversions after visiting the graph so
     // that the graph does not get polluted with these instructions
     // only necessary for this phase.
     removeRangeConversion();
+    // TODO(herhut): Find a better way to pass around ranges
+    (compiler.backend as JavaScriptBackend).optimizer.ranges = ranges;

[karlklose, 2014/03/12 14:43:45]

Do you want the explicit type check here?

Consider using a temporary variable instead.

[herhut, 2014/03/13 13:27:45]

Done.

   }
 
   void removeRangeConversion() {
     conversions.forEach((HRangeConversion instruction) {
       instruction.block.rewrite(instruction, instruction.inputs[0]);;
       instruction.block.remove(instruction);
     });
   }
 
   void visitBasicBlock(HBasicBlock block) {
@@ skipping 385 matching lines @@
   }
 
   Range handleBinaryOperation(HBinaryArithmetic instruction) {
     Range leftRange = visit(instruction.left);
     Range rightRange = visit(instruction.right);
     if (leftRange == null || rightRange == null) return null;
     BinaryOperation operation = instruction.operation(info.constantSystem);
     return operation.apply(leftRange, rightRange);
   }
 }