Detect total switches to prevent type pollution by default cases.

sdk/lib/_internal/compiler/implementation/ssa/nodes.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;
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
@@ skipping 1698 matching lines @@
   HConstant constant(int index) => inputs[index + 1];
   HInstruction get expression => inputs[0];
 
   /**
    * Provides the target to jump to if none of the constants match
    * the expression. If the switch had no default case, this is the
    * following join-block.
    */
   HBasicBlock get defaultTarget => block.successors.last;
 
+  /**
+   * Set to true if we statically know that the case statements
+   * are exhaustive wrt the range of the expression.
+   */
+  bool isTotal = false;
+
   accept(HVisitor visitor) => visitor.visitSwitch(this);
 
   String toString() => "HSwitch cases = $inputs";
 }
 
 abstract class HBinaryBitOp extends HInvokeBinary {
   HBinaryBitOp(left, right, selector, type)
       : super(left, right, selector, type);
 }
 
@@ skipping 1181 matching lines @@
 class HDynamicType extends HRuntimeType {
   HDynamicType(DynamicType dartType, TypeMask instructionType)
       : super(const <HInstruction>[], dartType, instructionType);
 
   accept(HVisitor visitor) => visitor.visitDynamicType(this);
 
   int typeCode() => HInstruction.DYNAMIC_TYPE_TYPECODE;
 
   bool typeEquals(HInstruction other) => other is HDynamicType;
 }