[parenscript-devel] APPLY of method functions - parenscript-devel - mailman3.common-lisp.net

19 Oct 2012


      Hello.
I have noticed that the macro APPLY in PS expands to a call to the  
function's apply method with an invariable “this” as its first  
argument (thisArg, per http://ecma-international.org/ecma-262/5.1/ 
#sec-15.3.4.3).  When the function is a method of an object, this may  
result in incorrect code.  Consider:
(lambda (some-vector start del-count &rest elts)
     ...
     (apply (@ some-vector splice) start del-count elts)
     ...
   )
=>
(function (someVector, start, delCount) {
       var elts = [];
       for (var i120 = 0; i120 < arguments.length - 3; i120 += 1) {
           elts[i120] = arguments[i120 + 3];
       };
       ...
       someVector.splice.apply(this, [start, delCount].concat(elts));
       ...
   });
Whereas, to be correct, the apply part should go like
someVector.splice.apply(someVector, [start, delCount].concat 
(elts));
Please find attached a patch which makes APPLY recognize property  
accessors in the function argument, separate them into object and  
method, and pass the object to the method's apply.  For cases which  
require more fine-grained control, the patch adds an APPLY-TO macro  
which provides for a completely custom thisArg.
There's also a separate patch with a couple of unit tests.
Yours,
  — B. Smilga.