implement opassign, fix bugs in pre/postfix, introduce a let* helper

lib/runtime/dart/isolate.js

 var isolate;
 (function(exports) {
   'use strict';
   class Capability extends core.Object {
     Capability() {
       return new _isolate_helper.CapabilityImpl();
     }
   }
   class IsolateSpawnException extends core.Object {
     IsolateSpawnException(message) {
@@ skipping 52 matching lines @@
     pause(resumeCapability) {
       if (resumeCapability === void 0)
         resumeCapability = null;
       if (resumeCapability == null)
         resumeCapability = new Capability();
       this[_pause](resumeCapability);
       return resumeCapability;
     }
     [_pause](resumeCapability) {
       let message = new core.List(3);
-      dart.dsetindex(message, 0, "pause");
-      dart.dsetindex(message, 1, this.pauseCapability);
-      dart.dsetindex(message, 2, resumeCapability);
+      message[core.$set](0, "pause");
+      message[core.$set](1, this.pauseCapability);
+      message[core.$set](2, resumeCapability);
       this.controlPort.send(message);
     }
     resume(resumeCapability) {
       let message = new core.List(2);
-      dart.dsetindex(message, 0, "resume");
-      dart.dsetindex(message, 1, resumeCapability);
+      message[core.$set](0, "resume");
+      message[core.$set](1, resumeCapability);
       this.controlPort.send(message);
     }
     addOnExitListener(responsePort) {
       let message = new core.List(2);
-      dart.dsetindex(message, 0, "add-ondone");
-      dart.dsetindex(message, 1, responsePort);
+      message[core.$set](0, "add-ondone");
+      message[core.$set](1, responsePort);
       this.controlPort.send(message);
     }
     removeOnExitListener(responsePort) {
       let message = new core.List(2);
-      dart.dsetindex(message, 0, "remove-ondone");
-      dart.dsetindex(message, 1, responsePort);
+      message[core.$set](0, "remove-ondone");
+      message[core.$set](1, responsePort);
       this.controlPort.send(message);
     }
     setErrorsFatal(errorsAreFatal) {
       let message = new core.List(3);
-      dart.dsetindex(message, 0, "set-errors-fatal");
-      dart.dsetindex(message, 1, this.terminateCapability);
-      dart.dsetindex(message, 2, errorsAreFatal);
+      message[core.$set](0, "set-errors-fatal");
+      message[core.$set](1, this.terminateCapability);
+      message[core.$set](2, errorsAreFatal);
       this.controlPort.send(message);
     }
     kill(priority) {
       if (priority === void 0)
         priority = Isolate.BEFORE_NEXT_EVENT;
       this.controlPort.send(new core.List.from(["kill", this.terminateCapability, priority]));
     }
     ping(responsePort, pingType) {
       if (pingType === void 0)
         pingType = Isolate.IMMEDIATE;
       let message = new core.List(3);
-      dart.dsetindex(message, 0, "ping");
-      dart.dsetindex(message, 1, responsePort);
-      dart.dsetindex(message, 2, pingType);
+      message[core.$set](0, "ping");
+      message[core.$set](1, responsePort);
+      message[core.$set](2, pingType);
       this.controlPort.send(message);
     }
     addErrorListener(port) {
       let message = new core.List(2);
-      dart.dsetindex(message, 0, "getErrors");
-      dart.dsetindex(message, 1, port);
+      message[core.$set](0, "getErrors");
+      message[core.$set](1, port);
       this.controlPort.send(message);
     }
     removeErrorListener(port) {
       let message = new core.List(2);
-      dart.dsetindex(message, 0, "stopErrors");
-      dart.dsetindex(message, 1, port);
+      message[core.$set](0, "stopErrors");
+      message[core.$set](1, port);
       this.controlPort.send(message);
     }
     get errors() {
       let controller = null;
       let port = null;
       // Function handleError: (dynamic) → void
       function handleError(message) {
         let errorDescription = dart.as(dart.dindex(message, 0), core.String);
         let stackDescription = dart.as(dart.dindex(message, 1), core.String);
         let error = new RemoteError(errorDescription, stackDescription);
@@ skipping 75 matching lines @@
   _RemoteStackTrace[dart.implements] = () => [core.StackTrace];
   // Exports:
   exports.Capability = Capability;
   exports.IsolateSpawnException = IsolateSpawnException;
   exports.Isolate = Isolate;
   exports.SendPort = SendPort;
   exports.ReceivePort = ReceivePort;
   exports.RawReceivePort = RawReceivePort;
   exports.RemoteError = RemoteError;
 })(isolate || (isolate = {}));