ES2020: fix String.prototype.matchAll type and description #62873

ljharb · 2025-12-09T21:32:34Z

(it would be very ideal to get this bugfix into v5, assuming v6 is the go implementation)

typescript-bot · 2025-12-09T21:32:38Z

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

typescript-bot · 2025-12-09T21:32:38Z

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

Copilot

Copilot wasn't able to review any files in this pull request.

typescript-bot · 2025-12-09T21:38:47Z

The TypeScript team hasn't accepted the linked issue #55843. If you can get it accepted, this PR will have a better chance of being reviewed.

DanielRosenwasser · 2025-12-10T23:38:45Z

v6 will be in TS, v7 will be the Go-based implementation.

ljharb · 2025-12-10T23:46:55Z

phew, thanks :-)

ljharb · 2025-12-11T18:08:51Z

Will this show up in the nightly v6 build the same day it's merged?

jakebailey · 2025-12-11T18:10:04Z

Yes.

For safety...

@typescript-bot test it

typescript-bot · 2025-12-11T18:10:08Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`test top400`	✅ Started	✅ Results
`user test this`	✅ Started	✅ Results
`run dt`	✅ Started	✅ Results
`perf test this faster`	✅ Started	👀 Results

typescript-bot · 2025-12-11T18:33:10Z

Hey @jakebailey, the results of running the DT tests are ready.

Everything looks the same!

You can check the log here.

typescript-bot · 2025-12-11T18:40:01Z

@jakebailey Here are the results of running the user tests with tsc comparing main and refs/pull/62873/merge:

There were infrastructure failures potentially unrelated to your change:

1 instance of "Git clone failed"

Otherwise...

Everything looks good!

typescript-bot · 2025-12-11T19:03:02Z

@jakebailey
The results of the perf run you requested are in!

Here they are:

tsc

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-Unions - node (v18.15.0, x64)}
_Errors	₁	₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_62,370	_62,370	_~	_~	_~	_{p=1.000 n=6}
_Types	_50,387	_50,387	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{195,549k (± 0.76%)}	_{193,712k (± 0.97%)}	_~	_192,474k	_196,157k	_{p=0.128 n=6}
_{Parse Time}	_{1.30s (± 1.02%)}	_{1.30s (± 0.63%)}	_~	_1.29s	_1.31s	_{p=0.402 n=6}
_{Bind Time}	_0.76s	_0.76s	_~	_~	_~	_{p=1.000 n=6}
_{Check Time}	_{9.84s (± 0.37%)}	_{9.88s (± 0.31%)}	_~	_9.85s	_9.92s	_{p=0.106 n=6}
_{Emit Time}	_{2.75s (± 0.55%)}	_{2.74s (± 0.90%)}	_~	_2.71s	_2.78s	_{p=0.627 n=6}
_{Total Time}	_{14.65s (± 0.38%)}	_{14.68s (± 0.20%)}	_~	_14.64s	_14.72s	_{p=0.418 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_955,823	_955,845	_{+22 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_415,853	_415,860	_{+7 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{1,253,902k (± 0.01%)}	_{1,253,878k (± 0.00%)}	_~	_1,253,845k	_1,253,926k	_{p=1.000 n=6}
_{Parse Time}	_{6.55s (± 0.58%)}	_{6.52s (± 0.69%)}	_~	_6.46s	_6.57s	_{p=0.170 n=6}
_{Bind Time}	_{1.96s (± 0.21%)}	_{1.96s (± 0.38%)}	_~	_1.95s	_1.97s	_{p=1.000 n=6}
_{Check Time}	_{32.41s (± 0.21%)}	_{32.32s (± 0.29%)}	_~	_32.21s	_32.48s	_{p=0.077 n=6}
_{Emit Time}	_{14.99s (± 0.56%)}	_{15.01s (± 0.41%)}	_~	_14.94s	_15.11s	_{p=0.422 n=6}
_{Total Time}	_{55.91s (± 0.21%)}	_{55.81s (± 0.22%)}	_~	_55.64s	_55.95s	_{p=0.173 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,723,733	_2,723,802	_{+69 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_937,508	_937,517	_{+9 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{3,051,590k (± 0.01%)}	_{3,051,643k (± 0.00%)}	_~	_3,051,512k	_3,051,788k	_{p=0.378 n=6}
_{Parse Time}	_{10.38s (± 1.29%)}	_{10.44s (± 0.71%)}	_~	_10.35s	_10.51s	_{p=0.629 n=6}
_{Bind Time}	_{2.79s (± 0.64%)}	_{2.78s (± 0.62%)}	_~	_2.76s	_2.80s	_{p=0.288 n=6}
_{Check Time}	_{112.63s (± 1.52%)}	_{111.50s (± 0.82%)}	_~	_110.67s	_113.18s	_{p=0.128 n=6}
_{Emit Time}	_{0.38s (± 3.33%)}	_{0.38s (± 1.99%)}	_~	_0.37s	_0.39s	_{p=0.788 n=6}
_{Total Time}	_{126.18s (± 1.37%)}	_{125.10s (± 0.78%)}	_~	_124.20s	_126.87s	_{p=0.128 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,252,077	_1,252,077	_~	_~	_~	_{p=1.000 n=6}
_Types	_259,856	_259,856	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,387,668k (± 0.04%)}	_{2,448,117k (± 6.08%)}	_~	_2,386,688k	_2,752,028k	_{p=0.689 n=6}
_{Parse Time}	_{5.16s (± 0.45%)}	_{5.17s (± 1.09%)}	_~	_5.09s	_5.24s	_{p=0.810 n=6}
_{Bind Time}	_{1.86s (± 0.79%)}	_{1.86s (± 0.63%)}	_~	_1.85s	_1.88s	_{p=0.680 n=6}
_{Check Time}	_{35.52s (± 0.60%)}	_{35.48s (± 0.92%)}	_~	_34.95s	_35.93s	_{p=0.810 n=6}
_{Emit Time}	_{3.05s (± 4.73%)}	_{3.00s (± 1.68%)}	_~	_2.96s	_3.10s	_{p=0.688 n=6}
_{Total Time}	_{45.59s (± 0.64%)}	_{45.53s (± 0.68%)}	_~	_45.10s	_46.02s	_{p=1.000 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,252,077	_1,252,077	_~	_~	_~	_{p=1.000 n=6}
_Types	_259,856	_259,856	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,061,581k (± 9.67%)}	_{3,183,091k (± 0.02%)}	_~	_3,181,841k	_3,183,718k	_{p=0.093 n=6}
_{Parse Time}	_{6.78s (± 0.94%)}	_{6.82s (± 0.75%)}	_~	_6.72s	_6.86s	_{p=0.378 n=6}
_{Bind Time}	_{2.26s (± 1.52%)}	_{2.27s (± 0.76%)}	_~	_2.24s	_2.29s	_{p=0.630 n=6}
_{Check Time}	_{43.00s (± 0.35%)}	_{43.28s (± 0.18%)}	_{+0.28s (+ 0.66%)}	_43.19s	_43.39s	_{p=0.005 n=6}
_{Emit Time}	_{3.52s (± 1.58%)}	_{3.50s (± 2.29%)}	_~	_3.39s	_3.59s	_{p=0.748 n=6}
_{Total Time}	_{55.58s (± 0.36%)}	_{55.88s (± 0.29%)}	_{+0.30s (+ 0.54%)}	_55.68s	_56.11s	_{p=0.037 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_264,690	_264,690	_~	_~	_~	_{p=1.000 n=6}
_Types	_104,069	_104,069	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{442,809k (± 0.02%)}	_{442,809k (± 0.02%)}	_~	_442,694k	_442,946k	_{p=1.000 n=6}
_{Parse Time}	_{2.84s (± 0.62%)}	_{2.85s (± 0.70%)}	_~	_2.83s	_2.88s	_{p=0.325 n=6}
_{Bind Time}	_1.16s	_{1.16s (± 0.45%)}	_~	_1.15s	_1.16s	_{p=0.174 n=6}
_{Check Time}	_{16.05s (± 0.43%)}	_{16.02s (± 0.32%)}	_~	_15.93s	_16.08s	_{p=0.574 n=6}
_{Emit Time}	_{1.31s (± 1.36%)}	_{1.31s (± 1.74%)}	_~	_1.29s	_1.34s	_{p=0.870 n=6}
_{Total Time}	_{21.36s (± 0.35%)}	_{21.34s (± 0.22%)}	_~	_21.25s	_21.37s	_{p=0.685 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₇₂	₇₂	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_225,493	_225,497	_{+4 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_94,373	_94,374	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{369,858k (± 0.03%)}	_{369,793k (± 0.02%)}	_~	_369,731k	_369,877k	_{p=0.471 n=6}
_{Parse Time}	_{2.85s (± 1.25%)}	_{2.85s (± 1.32%)}	_~	_2.81s	_2.90s	_{p=0.872 n=6}
_{Bind Time}	_{1.66s (± 1.42%)}	_{1.65s (± 1.29%)}	_~	_1.63s	_1.69s	_{p=0.627 n=6}
_{Check Time}	_{16.59s (± 0.27%)}	_{16.62s (± 0.49%)}	_~	_16.53s	_16.75s	_{p=0.686 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{21.11s (± 0.28%)}	_{21.13s (± 0.53%)}	_~	_21.02s	_21.27s	_{p=0.872 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₁₁	₁₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_4,069,745	_4,069,762	_{+17 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_1,283,244	_1,283,250	_{+6 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{3,859,060k (± 0.00%)}	_{3,859,106k (± 0.00%)}	_~	_3,859,009k	_3,859,199k	_{p=0.575 n=6}
_{Parse Time}	_{15.70s (± 0.61%)}	_{15.63s (± 0.54%)}	_~	_15.51s	_15.71s	_{p=0.148 n=6}
_{Bind Time}	_{5.40s (± 2.45%)}	_{5.40s (± 2.13%)}	_~	_5.29s	_5.55s	_{p=1.000 n=6}
_{Check Time}	_{113.16s (± 2.92%)}	_{112.58s (± 1.83%)}	_~	_110.03s	_114.47s	_{p=0.936 n=6}
_{Emit Time}	_{40.15s (± 5.63%)}	_{39.87s (± 4.88%)}	_~	_38.65s	_43.79s	_{p=0.873 n=6}
_{Total Time}	_{174.41s (± 3.11%)}	_{173.47s (± 1.41%)}	_~	_169.71s	_176.31s	_{p=0.810 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₄₀	₄₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_380,693	_380,693	_~	_~	_~	_{p=1.000 n=6}
_Types	_166,792	_166,792	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{539,527k (± 0.02%)}	_{539,517k (± 0.02%)}	_~	_539,416k	_539,631k	_{p=1.000 n=6}
_{Parse Time}	_{4.71s (± 0.62%)}	_{4.70s (± 0.46%)}	_~	_4.68s	_4.74s	_{p=0.366 n=6}
_{Bind Time}	_{2.03s (± 1.34%)}	_{2.04s (± 1.45%)}	_~	_1.99s	_2.08s	_{p=0.373 n=6}
_{Check Time}	_{22.89s (± 0.39%)}	_{22.96s (± 0.32%)}	_~	_22.83s	_23.03s	_{p=0.092 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{29.63s (± 0.33%)}	_{29.71s (± 0.18%)}	_~	_29.60s	_29.75s	_{p=0.054 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₃₀	₃₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_693,864	_693,877	_{+13 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_211,665	_211,672	_{+7 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{589,158k (± 0.03%)}	_{589,166k (± 0.02%)}	_~	_589,066k	_589,347k	_{p=0.378 n=6}
_{Parse Time}	_{4.17s (± 0.75%)}	_{4.16s (± 0.65%)}	_~	_4.13s	_4.20s	_{p=0.560 n=6}
_{Bind Time}	_{1.39s (± 1.48%)}	_{1.41s (± 0.39%)}	_~	_1.40s	_1.41s	_{p=0.360 n=6}
_{Check Time}	_{21.28s (± 1.94%)}	_{21.34s (± 1.48%)}	_~	_20.76s	_21.55s	_{p=0.689 n=6}
_{Emit Time}	_0.00s	_{0.00s (±244.70%)}	_~	_0.00s	_0.01s	_{p=0.405 n=6}
_{Total Time}	_{26.84s (± 1.59%)}	_{26.91s (± 1.21%)}	_~	_26.32s	_27.13s	_{p=0.688 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

Compiler-Unions - node (v18.15.0, x64)
angular-1 - node (v18.15.0, x64)
mui-docs - node (v18.15.0, x64)
self-build-src - node (v18.15.0, x64)
self-build-src-public-api - node (v18.15.0, x64)
self-compiler - node (v18.15.0, x64)
ts-pre-modules - node (v18.15.0, x64)
vscode - node (v18.15.0, x64)
webpack - node (v18.15.0, x64)
xstate-main - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

typescript-bot · 2025-12-11T19:33:49Z

@jakebailey Here are the results of running the top 400 repos with tsc comparing main and refs/pull/62873/merge:

Everything looks good!

bbrk24 · 2025-12-11T20:10:38Z

I'm not sure this actually resolves the linked issue -- the linked issue talks about passing custom objects that implement the [Symbol.matchAll] method, not just RegExp instances and strings.

ljharb · 2025-12-11T21:03:10Z

ah, that's true - it's more like the proper resolution to the incorrectly-closed #47310.

jakebailey · 2025-12-11T21:09:31Z

That's critical context. If I had known this was actually for that issue, I would not have approved and merged this PR.

It's well known that our lib types can be slightly more strict than "the spec technically allows this type because of implicit conversions". I could argue then that this function should accept number because that could be stringified, or something.

…62873)" This reverts commit bbb5322.

RyanCavanaugh · 2025-12-11T21:10:22Z

#47310 was correctly closed and this shouldn't have been merged.

This PR allows

const someStr = "(";
"foo".matchAll(someStr)

which throws a runtime error! It's super important that people understand that the argument is being regexified here

bbrk24 · 2025-12-11T21:12:20Z

Thankfully this is easy to test, and it does error:

ljharb · 2025-12-11T21:13:34Z

Then that's a major implementation bug - the spec does not say to do that. https://tc39.es/ecma262/#sec-string.prototype.matchall

ljharb · 2025-12-11T21:14:15Z

I will file implementation bugs for every affected engine, but matchAll absolutely should not coerce to a regexp.

RyanCavanaugh · 2025-12-11T21:15:05Z

@ljharb What is step 5 doing if not creating a regexp?

ljharb · 2025-12-11T21:16:20Z

shit, you're right. clearly my memory is incorrect, and i'm astonished it went in this way. Please do revert this PR, then, and I apologize for the confusion.

Renegade334 · 2025-12-11T23:07:04Z

FWIW, this would only have brought matchAll in line with the signature already used by match in lib.es5, which includes the coercion behaviour. If one isn't kosher, then should the other... well, match?

jakebailey · 2025-12-11T23:09:08Z

Yeah, if we have a string somewhere else, that is probably a mistake

ljharb · 2025-12-11T23:09:54Z

The more I've thought about it, the more I've realized that that was indeed the reason this horrific design choice was made - to be consistent with match.

So yes, I think either both should allow a string, or neither should, and I'm perfectly content for it to be "neither". (same with all the other regex-taking string methods)

ES2020: fix String.prototype.matchAll type and description

7decdc8

Copilot AI review requested due to automatic review settings December 9, 2025 21:32

github-project-automation bot added this to PR Backlog Dec 9, 2025

github-project-automation bot moved this to Not started in PR Backlog Dec 9, 2025

typescript-bot added the For Uncommitted Bug PR for untriaged, rejected, closed or missing bug label Dec 9, 2025

Copilot AI reviewed Dec 9, 2025

View reviewed changes

ljharb force-pushed the patch-2 branch 2 times, most recently from fa72d1b to 7decdc8 Compare December 9, 2025 22:11

DanielRosenwasser approved these changes Dec 10, 2025

View reviewed changes

github-project-automation bot moved this from Not started to Needs merge in PR Backlog Dec 10, 2025

jakebailey approved these changes Dec 11, 2025

View reviewed changes

jakebailey added this pull request to the merge queue Dec 11, 2025

Merged via the queue into microsoft:main with commit bbb5322 Dec 11, 2025
33 checks passed

github-project-automation bot moved this from Needs merge to Done in PR Backlog Dec 11, 2025

jakebailey added a commit that referenced this pull request Dec 11, 2025

Revert "ES2020: fix String.prototype.matchAll type and description (#…

6eb1f1c

…62873)" This reverts commit bbb5322.

jakebailey mentioned this pull request Dec 11, 2025

Revert "ES2020: fix String.prototype.matchAll type and description" #62885

Merged

ljharb deleted the patch-2 branch December 11, 2025 21:12

ES2020: fix String.prototype.matchAll type and description #62873

ES2020: fix String.prototype.matchAll type and description #62873

Conversation

ljharb commented Dec 9, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

typescript-bot commented Dec 9, 2025

Uh oh!

typescript-bot commented Dec 9, 2025

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Uh oh!

typescript-bot commented Dec 9, 2025

Uh oh!

DanielRosenwasser commented Dec 10, 2025

Uh oh!

ljharb commented Dec 10, 2025

Uh oh!

ljharb commented Dec 11, 2025

Uh oh!

jakebailey commented Dec 11, 2025

Uh oh!

typescript-bot commented Dec 11, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

typescript-bot commented Dec 11, 2025

Uh oh!

typescript-bot commented Dec 11, 2025

Uh oh!

typescript-bot commented Dec 11, 2025

tsc

Uh oh!

typescript-bot commented Dec 11, 2025

Uh oh!

Uh oh!

bbrk24 commented Dec 11, 2025

Uh oh!

ljharb commented Dec 11, 2025

Uh oh!

jakebailey commented Dec 11, 2025

Uh oh!

RyanCavanaugh commented Dec 11, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

bbrk24 commented Dec 11, 2025

Uh oh!

ljharb commented Dec 11, 2025

Uh oh!

ljharb commented Dec 11, 2025

Uh oh!

RyanCavanaugh commented Dec 11, 2025

Uh oh!

ljharb commented Dec 11, 2025

Uh oh!

Renegade334 commented Dec 11, 2025

Uh oh!

jakebailey commented Dec 11, 2025

Uh oh!

ljharb commented Dec 11, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

7 participants

ljharb commented Dec 9, 2025 •

edited

Loading

typescript-bot commented Dec 11, 2025 •

edited

Loading

RyanCavanaugh commented Dec 11, 2025 •

edited

Loading