Creates a function that, when called, either curries or invokes `func`
with an optional `this` binding and partially applied arguments.

@private
@param {Function|string} func The function or method name to reference.
@param {number} bitmask The bitmask of method flags to compose.
The bitmask may be composed of the following flags:
1 - `_.bind`
2 - `_.bindKey`
4 - `_.curry`
8 - `_.curry` (bound)
16 - `_.partial`
32 - `_.partialRight`
@param {Array} [partialArgs] An array of arguments to prepend to those
provided to the new function.
@param {Array} [partialRightArgs] An array of arguments to append to those
provided to the new function.
@param {*} [thisArg] The `this` binding of `func`.
@param {number} [arity] The arity of `func`.
@returns {Function} Returns the new bound function.
function createBound(func, bitmask, partialArgs, partialRightArgs, thisArg, arity) {
      var isBind = bitmask & 1,
          isBindKey = bitmask & 2,
          isCurry = bitmask & 4,
          isCurryBound = bitmask & 8,
          isPartial = bitmask & 16,
          isPartialRight = bitmask & 32,
          key = func;

      if (!isBindKey && !isFunction(func)) {
        throw new TypeError;
      }
      if (isPartial && !partialArgs.length) {
        bitmask &= ~16;
        isPartial = partialArgs = false;
      }
      if (isPartialRight && !partialRightArgs.length) {
        bitmask &= ~32;
        isPartialRight = partialRightArgs = false;
      }
      var bindData = func && func.__bindData__;
      if (bindData) {
        if (isBind && !(bindData[1] & 1)) {
          bindData[4] = thisArg;
        }
        if (!isBind && bindData[1] & 1) {
          bitmask |= 8;
        }
        if (isCurry && !(bindData[1] & 4)) {
          bindData[5] = arity;
        }
        if (isPartial) {
          push.apply(bindData[2] || (bindData[2] = []), partialArgs);
        }
        if (isPartialRight) {
          push.apply(bindData[3] || (bindData[3] = []), partialRightArgs);
        }
        bindData[1] |= bitmask;
        return createBound.apply(null, bindData);
      }
      // use `Function#bind` if it exists and is fast
      // (in V8 `Function#bind` is slower except when partially applied)
      if (isBind && !(isBindKey || isCurry || isPartialRight) &&
          (support.fastBind || (nativeBind && isPartial))) {
        if (isPartial) {
          var args = [thisArg];
          push.apply(args, partialArgs);
        }
        var bound = isPartial
          ? nativeBind.apply(func, args)
          : nativeBind.call(func, thisArg);
      }
      else {
        bound = function() {
          // `Function#bind` spec
          // http://es5.github.io/#x15.3.4.5
          var args = arguments,
              thisBinding = isBind ? thisArg : this;

          if (isCurry || isPartial || isPartialRight) {
            args = nativeSlice.call(args);
            if (isPartial) {
              unshift.apply(args, partialArgs);
            }
            if (isPartialRight) {
              push.apply(args, partialRightArgs);
            }
            if (isCurry && args.length < arity) {
              bitmask |= 16 & ~32;
              return createBound(func, (isCurryBound ? bitmask : bitmask & ~3), args, null, thisArg, arity);
            }
          }
          if (isBindKey) {
            func = thisBinding[key];
          }
          if (this instanceof bound) {
            // ensure `new bound` is an instance of `func`
            thisBinding = createObject(func.prototype);

            // mimic the constructor's `return` behavior
            // http://es5.github.io/#x13.2.2
            var result = func.apply(thisBinding, args);
            return isObject(result) ? result : thisBinding;
          }
          return func.apply(thisBinding, args);
        };
      }
      setBindData(bound, nativeSlice.call(arguments));
      return bound;
    }