destructuring-pattern-parenthesized.js

// Any copyright is dedicated to the Public Domain.

// http://creativecommons.org/licenses/publicdomain/

//-----------------------------------------------------------------------------

var BUGNUMBER = 1146136;

var summary =

  'Parenthesized "destructuring patterns" are not usable as destructuring ' +

  'patterns';

print(BUGNUMBER + ": " + summary);

/**************

 * BEGIN TEST *

 **************/

// Don't pollute the top-level script with eval references.

var savedEval = this[String.fromCharCode(101, 118, 97, 108)];

function checkError(code, nonstrictErr, strictErr)

  function helper(exec, prefix, err)

    var fullCode = prefix + code;

try

      var f = exec(fullCode);

      var error =

        "no early error, parsed code <" + fullCode + "> using " + exec.name;

      if (typeof f === "function")

try

          f();

          error += ", and the function can be called without error";

        catch (e)

          error +=", and calling the function throws " + e;

      throw new Error(error);

    catch (e)

      assertEq(e instanceof err, true,

               "expected " + err.name + ", got " + e + " " +

               "for code <" + fullCode + "> when parsed using " + exec.name);

  helper(Function, "", nonstrictErr);

  helper(Function, "'use strict'; ", strictErr);

  helper(savedEval, "", nonstrictErr);

  helper(savedEval, "'use strict'; ", strictErr);

// Parenthesized destructuring patterns don't trigger grammar refinement, so we

// get the usual SyntaxError for an invalid assignment target, per

// 12.14.1 second bullet.

checkError("var a, b; ([a, b]) = [1, 2];", SyntaxError, SyntaxError);

checkError("var a, b; ({a, b}) = { a: 1, b: 2 };", SyntaxError, SyntaxError);

// *Nested* parenthesized destructuring patterns, on the other hand, do trigger

// grammar refinement.  But subtargets in a destructuring pattern must be

// either object/array literals that match the destructuring pattern refinement

// *or* valid simple assignment targets (or such things with a default, with the

// entire subtarget unparenthesized: |a = 3| is fine, |(a) = 3| is fine for

// destructuring in an expression, |(a = 3)| is forbidden).  Parenthesized

// object/array patterns are neither.  And so 12.14.5.1 third bullet requires an

// early SyntaxError.

checkError("var a, b; ({ a: ({ b: b }) } = { a: { b: 42 } });", SyntaxError, SyntaxError);

checkError("var a, b; ({ a: { b: (b = 7) } } = { a: {} });", SyntaxError, SyntaxError);

checkError("var a, b; ({ a: ([b]) } = { a: [42] });", SyntaxError, SyntaxError);

checkError("var a, b; [(a = 5)] = [1];", SyntaxError, SyntaxError);

checkError("var a, b; ({ a: (b = 7)} = { b: 1 });", SyntaxError, SyntaxError);

Function("var a, b; [(a), b] = [1, 2];")();

Function("var a, b; [(a) = 5, b] = [1, 2];")();

Function("var a, b; [(arguments), b] = [1, 2];")();

Function("var a, b; [(arguments) = 5, b] = [1, 2];")();

Function("var a, b; [(eval), b] = [1, 2];")();

Function("var a, b; [(eval) = 5, b] = [1, 2];")();

var repair = {}, demolition = {};

Function("var a, b; [(repair.man), b] = [1, 2];")();

Function("var a, b; [(demolition['man']) = 'motel', b] = [1, 2];")();

Function("var a, b; [(demolition['man' + {}]) = 'motel', b] = [1, 2];")(); // evade constant-folding

function classesEnabled()

try

    new Function("class B { constructor() { } }; class D extends B { constructor() { super(); } }");

    return true;

  catch (e) {

    if (!(e instanceof SyntaxError))

      throw e;

    return false;

if (classesEnabled())

  Function("var a, b; var obj = { x() { [(super.man), b] = [1, 2]; } };")();

  Function("var a, b; var obj = { x() { [(super[8]) = 'motel', b] = [1, 2]; } };")();

  Function("var a, b; var obj = { x() { [(super[8 + {}]) = 'motel', b] = [1, 2]; } };")(); // evade constant-folding

// As noted above, when the assignment element has an initializer, the

// assignment element must not be parenthesized.

checkError("var a, b; [(repair.man = 17)] = [1];", SyntaxError, SyntaxError);

checkError("var a, b; [(demolition['man'] = 'motel')] = [1, 2];", SyntaxError, SyntaxError);

checkError("var a, b; [(demolition['man' + {}] = 'motel')] = [1];", SyntaxError, SyntaxError); // evade constant-folding

if (classesEnabled())

  checkError("var a, b; var obj = { x() { [(super.man = 5)] = [1]; } };", SyntaxError, SyntaxError);

  checkError("var a, b; var obj = { x() { [(super[8] = 'motel')] = [1]; } };", SyntaxError, SyntaxError);

  checkError("var a, b; var obj = { x() { [(super[8 + {}] = 'motel')] = [1]; } };", SyntaxError, SyntaxError); // evade constant-folding

checkError("var a, b; [f() = 'ohai', b] = [1, 2];", SyntaxError, SyntaxError);

checkError("var a, b; [(f()) = 'kthxbai', b] = [1, 2];", SyntaxError, SyntaxError);

Function("var a, b; ({ a: (a), b} = { a: 1, b: 2 });")();

Function("var a, b; ({ a: (a) = 5, b} = { a: 1, b: 2 });")();

/******************************************************************************/

if (typeof reportCompare === "function")

  reportCompare(true, true);

print("Tests complete");