spread-call-length.js

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load(libdir + 'iteration.js');

let makeCall    = farg => Function("f", "arg", "return f(" + farg + ");");

let makeFunCall = farg => Function("f", "arg", "return f.call(null, " + farg + ");");

let makeNew     = farg => Function("f", "arg", "return new f(" + farg + ").length;");

function checkLength(f, makeFn) {

  assertEq(makeFn("...[1, 2, 3]")(f), 3);

  assertEq(makeFn("1, ...[2], 3")(f), 3);

  assertEq(makeFn("1, ...[2], ...[3]")(f), 3);

  assertEq(makeFn("1, ...[2, 3]")(f), 3);

  assertEq(makeFn("1, ...[], 2, 3")(f), 3);

  assertEq(makeFn("...[1]")(f), 1);

  assertEq(makeFn("...[1, 2]")(f), 2);

  assertEq(makeFn("...[1, 2, 3, 4]")(f), 4);

  assertEq(makeFn("1, ...[2, 3, 4], 5")(f), 5);

  assertEq(makeFn("...[undefined]")(f), 1);

  // other iterable objects

  assertEq(makeFn("...arg")(f, new Int32Array([1, 2, 3])), 3);

  assertEq(makeFn("...arg")(f, "abc"), 3);

  assertEq(makeFn("...arg")(f, [1, 2, 3][Symbol.iterator]()), 3);

  assertEq(makeFn("...arg")(f, new Set([1, 2, 3])), 3);

  assertEq(makeFn("...arg")(f, new Map([["a", "A"], ["b", "B"], ["c", "C"]])), 3);

  let itr = {};

  itr[Symbol.iterator] = function() {

      return {

          i: 1,

          next: function() {

              if (this.i < 4)

                  return { value: this.i++, done: false };

              else

                  return { value: undefined, done: true };

};

  assertEq(makeFn("...arg")(f, itr), 3);

  function* gen() {

      for (let i = 1; i < 4; i ++)

          yield i;

  assertEq(makeFn("...arg")(f, gen()), 3);

checkLength(function(x) { return arguments.length; }, makeCall);

checkLength(function(x) { return arguments.length; }, makeFunCall);

function lengthClass(x) {

  this.length = arguments.length;

checkLength(lengthClass, makeNew);