Commit ef3d7d2f authored by Matthew Gaudet's avatar Matthew Gaudet
Browse files

Bug 1833946 - Normative Change: Remove double construction in Array.fromAsync r=arai 

Differential Revision: https://phabricator.services.mozilla.com/D178474
parent 383cfa85

js/src/builtin/Array.js

+11 −9
Original line number Diff line number Diff line
@@ -834,6 +834,8 @@ function ArrayKeys() { 


#ifdef NIGHTLY_BUILD

// https://tc39.es/proposal-array-from-async/

// TODO: Bug 1834560 The step numbers in this will need updating when this is merged

// into the main spec.

function ArrayFromAsync(asyncItems, mapfn = undefined, thisArg = undefined) {

  // Step 1. Let C be the this value.

  var C = this;
@@ -877,12 +879,6 @@ function ArrayFromAsync(asyncItems, mapfn = undefined, thisArg = undefined) { 
      }

    }



    // Step 3.e. If IsConstructor(C) is true, then

    //     Step 3.e.i. Let A be ? Construct(C).

    // Step 3.f. Else,

    //     Step 3.f.i. Let A be ! ArrayCreate(0).

    let A = IsConstructor(C) ? constructContentFunction(C, C) : [];



    // Step 3.g. Let iteratorRecord be undefined.

    // Step 3.j. If iteratorRecord is not undefined, then ...

    if (usingAsyncIterator !== undefined || usingSyncIterator !== undefined) {
@@ -898,6 +894,14 @@ function ArrayFromAsync(asyncItems, mapfn = undefined, thisArg = undefined) { 
      // Step 3.i. Else if usingSyncIterator is not undefined, then

      //     Set iteratorRecord to ? CreateAsyncFromSyncIterator(GetIterator(asyncItems, sync, usingSyncIterator)).



      // https://github.com/tc39/proposal-array-from-async/pull/41

      // Step 3.e. If IsConstructor(C) is true, then

      //     Step 3.e.i. Let A be ? Construct(C).

      // Step 3.f. Else,

      //     Step 3.f.i. Let A be ! ArrayCreate(0).

      let A = IsConstructor(C) ? constructContentFunction(C, C) : [];





      // Step 3.j.i. Let k be 0.

      let k = 0;
@@ -964,9 +968,7 @@ function ArrayFromAsync(asyncItems, mapfn = undefined, thisArg = undefined) { 
    //     Step 3.k.iv.1. Let A be ? Construct(C, « 𝔽(len) »).

    // Step 3.k.v. Else,

    //     Step 3.k.v.1. Let A be ? ArrayCreate(len).

    // Note: This double construction isn't great, issue is open:

    // https://github.com/tc39/proposal-array-from-async/issues/35

    A = IsConstructor(C) ? constructContentFunction(C, C, len) : std_Array(len);

    let A = IsConstructor(C) ? constructContentFunction(C, C, len) : std_Array(len);



    // Step 3.k.vi. Let k be 0.

    let k = 0;