'use strict';
  
  var toPosInt = require('../number/to-pos-integer')
  
    , test = function (a, b) {}, desc, defineProperty
    , generate, mixin;
  
  try {
  	Object.defineProperty(test, 'length', { configurable: true, writable: false,
  		enumerable: false, value: 1 });
  } catch (ignore) {}
  
  if (test.length === 1) {
  	// ES6
  	desc = { configurable: true, writable: false, enumerable: false };
  	defineProperty = Object.defineProperty;
  	module.exports = function (fn, length) {
  		length = toPosInt(length);
  		if (fn.length === length) return fn;
  		desc.value = length;
  		return defineProperty(fn, 'length', desc);
  	};
  } else {
  	mixin = require('../object/mixin');
  	generate = (function () {
  		var cache = [];
  		return function (l) {
  			var args, i = 0;
  			if (cache[l]) return cache[l];
  			args = [];
  			while (l--) args.push('a' + (++i).toString(36));
  			return new Function('fn', 'return function (' + args.join(', ') +
  				') { return fn.apply(this, arguments); };');
  		};
  	}());
  	module.exports = function (src, length) {
  		var target;
  		length = toPosInt(length);
  		if (src.length === length) return src;
  		target = generate(length)(src);
  		try { mixin(target, src); } catch (ignore) {}
  		return target;
  	};
  }