Merge branch 'use-property-for-suspension-check'

Author: LeszekSwirski

src/compile.js

@@ -318,13 +318,13 @@ Compiler.prototype._checkSuspension = function(e) {
 
         e = e || {lineno: "currLineNo", col_offset: "currColNo"};
 
-        out ("if ($ret instanceof Sk.misceval.Suspension) { return $saveSuspension($ret,'"+this.filename+"',"+e.lineno+","+e.col_offset+"); }");
+        out ("if ($ret && $ret.isSuspension) { return $saveSuspension($ret,'"+this.filename+"',"+e.lineno+","+e.col_offset+"); }");
 
         this.u.doesSuspend = true;
         this.u.tempsToSave = this.u.tempsToSave.concat(this.u.localtemps);
 
     } else {
-        out ("if ($ret instanceof Sk.misceval.Suspension) { $ret = Sk.misceval.retryOptionalSuspensionOrThrow($ret); }");
+        out ("if ($ret && $ret.isSuspension) { $ret = Sk.misceval.retryOptionalSuspensionOrThrow($ret); }");
     }
 };
 Compiler.prototype.ctuplelistorset = function(e, data, tuporlist) {

src/misceval.js

@@ -17,6 +17,7 @@ Sk.misceval = {};
  * @param{Object=} data Data attached to this suspension. Will be copied from child if not supplied.
  */
 Sk.misceval.Suspension = function Suspension(resume, child, data) {
+    this.isSuspension = true;
     if (resume !== undefined && child !== undefined) {
         this.resume = function() { return resume(child.resume()); };
     }