dart2js cps: Use definitions by default, not references.

pkg/compiler/lib/src/cps_ir/finalize.dart

Index: pkg/compiler/lib/src/cps_ir/finalize.dart
diff --git a/pkg/compiler/lib/src/cps_ir/finalize.dart b/pkg/compiler/lib/src/cps_ir/finalize.dart
index dad9e51dd3d6f887593b6a8a140b6595c7425163..937680030fd640de3e66b9a7a39ad78f93d23608 100644
--- a/pkg/compiler/lib/src/cps_ir/finalize.dart
+++ b/pkg/compiler/lib/src/cps_ir/finalize.dart
@@ -38,11 +38,11 @@ class Finalize extends TrampolineRecursiveVisitor implements Pass {
   CpsFragment visitBoundsCheck(BoundsCheck node) {
     CpsFragment cps = new CpsFragment(node.sourceInformation);
     if (node.hasNoChecks) {
-      node..replaceUsesWith(node.object.definition)..destroy();
+      node..replaceUsesWith(node.object)..destroy();
       return cps;
     }
     Continuation fail = cps.letCont();
-    Primitive index = node.index.definition;
+    Primitive index = node.index;
     if (node.hasIntegerCheck) {
       cps.ifTruthy(cps.applyBuiltin(BuiltinOperator.IsNotUnsigned32BitInteger,
           [index, index]))
@@ -53,7 +53,7 @@ class Finalize extends TrampolineRecursiveVisitor implements Pass {
           .invokeContinuation(fail);
     }
     if (node.hasUpperBoundCheck) {
-      Primitive length = node.length.definition;
+      Primitive length = node.length;
       if (length is GetLength &&
           length.hasExactlyOneUse &&
           areAdjacent(length, node)) {
@@ -69,19 +69,19 @@ class Finalize extends TrampolineRecursiveVisitor implements Pass {
     }
     if (node.hasEmptinessCheck) {
       cps.ifTruthy(cps.applyBuiltin(BuiltinOperator.StrictEq,
-          [node.length.definition, cps.makeZero()]))
+          [node.length, cps.makeZero()]))
           .invokeContinuation(fail);
     }
     cps.insideContinuation(fail).invokeStaticThrower(
           helpers.throwIndexOutOfRangeException,
-          [node.object.definition, index]);
-    node..replaceUsesWith(node.object.definition)..destroy();
+          [node.object, index]);
+    node..replaceUsesWith(node.object)..destroy();
     return cps;
   }
 
   void visitGetStatic(GetStatic node) {
-    if (node.witness != null) {
-      node..witness.unlink()..witness = null;
+    if (node.witnessRef != null) {
+      node..witnessRef.unlink()..witnessRef = null;
     }
   }
 
@@ -92,9 +92,8 @@ class Finalize extends TrampolineRecursiveVisitor implements Pass {
       // type of an object is immutable, but the type of an array can change
       // after allocation.  After the finalize pass, this assumption is no
       // longer needed, so we can replace the remaining idenitity templates.
-      Refinement refinement = new Refinement(
-          node.arguments.single.definition,
-          node.type)..type = node.type;
+      Refinement refinement = new Refinement(node.argument(0), node.type)

[sra1, 2016/03/01 17:59:53]

I'm ok with it, but this no longer implicitly asserts there is a single
argument.

+          ..type = node.type;
       node.replaceWith(refinement);
     }
   }