Revert "Implement substitution for type variables."

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 visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
@@ skipping 2264 matching lines @@
 class HIs extends HInstruction {
   final DartType typeExpression;
   final bool nullOk;
 
   HIs(this.typeExpression, List<HInstruction> inputs, {this.nullOk: false})
      : super(inputs) {
     setUseGvn();
   }
 
   HInstruction get expression => inputs[0];
-  HInstruction get checkCall => inputs[1];
+  HInstruction getCheck(int index) => inputs[index + 1];
+  int get checkCount => inputs.length - 1;
 
-  bool hasArgumentsCheck() => inputs.length > 1;
+  bool hasArgumentChecks() => inputs.length > 1;
 
   HType get guaranteedType => HType.BOOLEAN;
 
   accept(HVisitor visitor) => visitor.visitIs(this);
 
   toString() => "$expression is $typeExpression";
 
   int typeCode() => HInstruction.IS_TYPECODE;
   bool typeEquals(HInstruction other) => other is HIs;
   bool dataEquals(HIs other) {
@@ skipping 403 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty);
     return statements.last.end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }