dart2js cps: Refactor CallExpressions into Primitives.

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

 library dart2js.cps_ir_integrity;
 
 import 'cps_ir_nodes.dart';
 import 'cps_ir_nodes_sexpr.dart';
 import '../tracer.dart' as tracer;
 
 /// Dump S-expressions on error if the tracer is enabled.
 ///
 /// Technically this has nothing to do with the tracer, but if you want one
 /// enabled, you typically want the other as well, so we use the same flag.
@@ skipping 136 matching lines @@
     }
     visit(node.body);
   }
 
   @override
   processReference(Reference ref) {
     Definition def = ref.definition;
     if (inScope[def] == ScopeType.NotInScope) {
       error('Referenced out of scope: $def', ref);
     }
+    if (ref.previous == ref) {
+      error('Shared Reference object to $def', ref);
+    }
     if (ref.previous == null && def.firstRef != ref ||
         ref.previous != null && ref.previous.next != ref) {
       error('Broken .previous link in reference to $def', def);
     }
     ref.previous = ref; // Mark reference as "seen". We will repair it later.
   }
 
   @override
   processInvokeContinuation(InvokeContinuation node) {
     Continuation target = node.continuation.definition;
@@ skipping 78 matching lines @@
   }
 
   @override
   processReference(Reference node) {
     if (node.parent != _parent) {
       error('Parent pointer on $node is ${node.parent} but should be $_parent',
             node);
     }
   }
 }