Remove old code.

lib/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.
 
 interface HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
   R visitBitXor(HBitXor node);
@@ skipping 1244 matching lines @@
 }
 
 class HFieldGet extends HFieldAccess {
   final bool isFinalOrConst;
 
   HFieldGet(Element element, HInstruction receiver,
             [this.isFinalOrConst = false])
       : super(element, <HInstruction>[receiver]);
   HFieldGet.fromActivation(receiver) : this(null, receiver);
 
-  HInstruction get receiver() => inputs.length == 1 ? inputs[0] : null;
+  HInstruction get receiver() => inputs[0];
 
   accept(HVisitor visitor) => visitor.visitFieldGet(this);
 
   void prepareGvn() {
     setUseGvn();
     if (!isFinalOrConst) setDependsOnSomething();
   }
 
   int typeCode() => 27;
   bool typeEquals(other) => other is HFieldGet;
   bool dataEquals(HFieldGet other) => element == other.element;
 }
 
 class HFieldSet extends HFieldAccess {
   HFieldSet(Element element, HInstruction receiver, HInstruction value)
       : super(element, <HInstruction>[receiver, value]);
   HFieldSet.fromActivation(receiver, value)
       : this(null, receiver, value);
 
-  HInstruction get receiver() => inputs.length == 2 ? inputs[0] : null;
-  HInstruction get value() => inputs.length == 2 ? inputs[1] : inputs[0];
+  HInstruction get receiver() => inputs[0];
+  HInstruction get value() => inputs[1];
   accept(HVisitor visitor) => visitor.visitFieldSet(this);
 
   void prepareGvn() {
     // TODO(ngeoffray): implement more fine grain side effects.
     setAllSideEffects();
   }
 
   bool isStatement() => true;
 }
 
@@ skipping 1285 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);
 }