fix(parser): allow `in` in array literals in a `for` statement initializer by JemmyIndex · Pull Request #65330 · microsoft/TypeScript

Jemmy (JemmyIndex) · 2026-11-05T06:54:45Z

The [~In] parameter of a for statement head does not reach into array literals — ElementList : AssignmentExpression[+In] — but parseArrayLiteralExpression parsed its elements in the caller's context, so the DisallowInContext flag set for a for initializer leaked into the element list:

const o = { a: 1 }, k = "a";
for (let i = 0, has = [k in o]; i < 1; i++) {} // TS1005: ',' expected.
let x: any;
for ([x = "x" in {}] of [[]]) {}               // TS1005: ',' expected.

The neighbouring productions already clear the flag — object literal property values (parseObjectLiteralExpression → doInContext(DisallowInContext, false, …)) and call arguments (parseArgumentExpression) — so this does the same for array literal elements. That also fixes the destructuring-assignment form in a for-of head, which test262 covers in language/statements/for-of/dstr/array-elem-init-in.js.

Only the tokens between [ and ] are affected: the flag is restored once the ] is consumed, so for (x in y) and for ([a, b] in y) parse exactly as before (and still report TS2491), and emit is unchanged.

Added tests/cases/compiler/arrayLiteralInOperatorInForInitializer.ts, covering a plain for initializer, comma and nested elements, an array pattern in a for-of head, and the unchanged for-in behavior.

Verification: go test ./internal/parser/... and the full go test ./internal/testrunner (compiler + conformance baselines) pass.

AI assistance

This PR was written with AI assistance, and the change is deliberately scoped to clearing the DisallowInContext flag while parsing array literal elements. I verified the behavior manually: both repros from the issue parse cleanly, for (x in y) and for ([a, b] in y) still report TS2491, and emit is unchanged. go test ./internal/parser/... and the full go test ./internal/testrunner pass locally. I understand the implementation and am happy to answer questions about it.

The [~In] of a for statement head does not reach into array literals (ElementList : AssignmentExpression[+In]), but parseArrayLiteralExpression parsed its elements in the caller's context, so the DisallowInContext flag leaked into the element list. Clear it the same way parseArgumentExpression and object literal property values already do.

Copilot

🟢 Approval recommended

No active review issues were identified for the parser change allowing in inside array literals in for initializers.

No open issues 🎉

What changed in this PR

Fixes #65311 by allowing the in operator inside array literals in for initializers, aligning the native TypeScript parser with JavaScript grammar.

Changes:

Clears DisallowInContext while parsing array elements, then restores the surrounding context.
Adds regression coverage for array expressions, for-of destructuring defaults, and ordinary for-in parsing.
Adds expected JavaScript, type, and symbol baselines.

File	Description
`tsc/testdata/tests/cases/compiler/arrayLiteralInOperatorInForInitializer.ts`	Adds regression cases for `in` in loop-head arrays.
`tsc/testdata/baselines/reference/compiler/arrayLiteralInOperatorInForInitializer.types`	Records expected expression types.
`tsc/testdata/baselines/reference/compiler/arrayLiteralInOperatorInForInitializer.symbols`	Records expected symbol bindings.
`tsc/testdata/baselines/reference/compiler/arrayLiteralInOperatorInForInitializer.js`	Records expected JavaScript output.
`tsc/internal/parser/parser.go`	Allows `in` while parsing array literal elements.

_{Review effort: Balanced}

Ryan Cavanaugh (RyanCavanaugh) · 2026-11-05T17:42:41Z

TypeScript Bot (@typescript-bot) test it

typescript-automation · 2026-11-05T17:42:47Z

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-automation · 2026-11-05T18:15:38Z

Hey Ryan Cavanaugh (@RyanCavanaugh), the results of running the DT tests are ready.

Everything looks the same!

You can check the log here.

typescript-automation · 2026-11-05T18:21:40Z

Ryan Cavanaugh (@RyanCavanaugh) Here are the results of running the user tests with tsc comparing baseline and pr:

Everything looks good!

typescript-automation · 2026-11-05T18:36:12Z

Ryan Cavanaugh (@RyanCavanaugh)
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 - native}
_Errors	₄₁	₄₁	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_88,466	_88,466	_~	_~	_~	_{p=1.000 n=20}
_Types	_79,607	_79,607	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{106,393k (± 0.02%)}	_{106,423k (± 0.03%)}	_~	_106,282k	_106,528k	_{p=0.144 n=20}
_{Memory Allocs}	_{1,262,018 (± 0.01%)}	_{1,261,927 (± 0.01%)}	_~	_1,261,491	_1,262,191	_{p=0.280 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.022s (± 2.86%)}	_{0.023s (± 3.10%)}	_~	_0.019s	_0.025s	_{p=0.358 n=20}
_{Bind Time}	_{0.008s (± 5.47%)}	_{0.008s (± 4.78%)}	_~	_0.007s	_0.010s	_{p=0.957 n=20}
_{Check Time}	_{0.203s (± 0.73%)}	_{0.203s (± 0.67%)}	_~	_0.199s	_0.208s	_{p=0.835 n=20}
_{Emit Time}	_{0.130s (± 0.96%)}	_{0.129s (± 0.70%)}	_~	_0.125s	_0.133s	_{p=0.781 n=20}
_{Total Time}	_{0.366s (± 0.51%)}	_{0.367s (± 0.37%)}	_~	_0.362s	_0.373s	_{p=0.548 n=20}
_{angular-1 - native}
_Errors	₆₃	₆₃	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_756,637	_756,637	_~	_~	_~	_{p=1.000 n=20}
_Types	_549,451	_549,451	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{644,068k (± 0.02%)}	_{644,053k (± 0.02%)}	_~	_643,516k	_644,513k	_{p=0.805 n=20}
_{Memory Allocs}	_{9,545,869 (± 0.09%)}	_{9,546,216 (± 0.08%)}	_~	_9,532,107	_9,584,935	_{p=0.678 n=20}
_{Config Time}	_{0.008s (± 1.77%)}	_0.008s	_~	_~	_~	_{p=0.487 n=20}
_{Parse Time}	_{0.117s (± 1.96%)}	_{0.117s (± 2.49%)}	_~	_0.106s	_0.130s	_{p=0.773 n=20}
_{Bind Time}	_{0.040s (±11.24%)}	_{0.040s (± 9.16%)}	_~	_0.034s	_0.059s	_{p=0.326 n=20}
_{Check Time}	_{0.615s (± 1.07%)}	_{0.614s (± 1.18%)}	_~	_0.587s	_0.631s	_{p=0.825 n=20}
_{Emit Time}	_{0.390s (± 0.93%)}	_{0.391s (± 0.65%)}	_~	_0.383s	_0.403s	_{p=0.217 n=20}
_{Total Time}	_{1.182s (± 0.52%)}	_{1.183s (± 0.59%)}	_~	_1.160s	_1.212s	_{p=0.815 n=20}
_{arktype - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_686,116	_686,116	_~	_~	_~	_{p=1.000 n=20}
_Types	_939,797	_939,797	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{475,942k (± 0.01%)}	_{476,013k (± 0.01%)}	_~	_475,809k	_476,212k	_{p=0.057 n=20}
_{Memory Allocs}	_{12,059,384 (± 0.02%)}	_{12,058,554 (± 0.01%)}	_~	_12,055,021	_12,065,615	_{p=0.565 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.042s (± 3.28%)}	_{0.041s (± 2.79%)}	_~	_0.036s	_0.047s	_{p=0.269 n=20}
_{Bind Time}	_{0.014s (±10.83%)}	_{0.012s (± 6.03%)}	_~	_0.011s	_0.018s	_{p=0.381 n=20}
_{Check Time}	_{0.831s (± 0.48%)}	_{0.837s (± 0.71%)}	_~	_0.817s	_0.864s	_{p=0.095 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.915s (± 0.39%)}	_{0.918s (± 0.66%)}	_~	_0.895s	_0.945s	_{p=0.365 n=20}
_{class-transformer - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_45,376	_45,376	_~	_~	_~	_{p=1.000 n=20}
_Types	_7,573	_7,573	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{27,748k (± 0.03%)}	_{27,749k (± 0.02%)}	_~	_27,731k	_27,776k	_{p=0.857 n=20}
_{Memory Allocs}	_{248,275 (± 0.07%)}	_{248,335 (± 0.06%)}	_~	_247,947	_249,335	_{p=0.805 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.011s (± 3.85%)}	_{0.011s (± 2.80%)}	_~	_0.010s	_0.012s	_{p=1.000 n=20}
_{Bind Time}	_{0.004s (±10.39%)}	_{0.004s (±13.12%)}	_~	_0.002s	_0.005s	_{p=0.690 n=20}
_{Check Time}	_{0.007s (± 7.42%)}	_{0.007s (± 6.88%)}	_~	_0.006s	_0.009s	_{p=0.885 n=20}
_{Emit Time}	_{0.008s (± 7.15%)}	_{0.008s (± 7.24%)}	_~	_0.006s	_0.010s	_{p=0.816 n=20}
_{Total Time}	_{0.031s (± 1.63%)}	_{0.031s (± 2.09%)}	_~	_0.028s	_0.033s	_{p=0.915 n=20}
_{effect - native}
_Errors	₁₂	₁₂	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_1,235,134	_1,235,134	_~	_~	_~	_{p=1.000 n=20}
_Types	_893,436	_893,436	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{941,660k (± 0.02%)}	_{941,516k (± 0.02%)}	_~	_940,806k	_942,220k	_{p=0.277 n=20}
_{Memory Allocs}	_{12,626,413 (± 0.06%)}	_{12,625,720 (± 0.04%)}	_~	_12,610,799	_12,647,377	_{p=0.758 n=20}
_{Config Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.148s (± 1.20%)}	_{0.149s (± 2.36%)}	_~	_0.138s	_0.169s	_{p=1.000 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.861s (± 0.81%)}	_{0.861s (± 0.74%)}	_~	_0.839s	_0.885s	_{p=0.984 n=20}
_{Emit Time}	_{0.485s (± 1.20%)}	_{0.481s (± 1.17%)}	_~	_0.455s	_0.506s	_{p=0.245 n=20}
_{Total Time}	_{1.583s (± 0.42%)}	_{1.583s (± 0.42%)}	_~	_1.559s	_1.621s	_{p=0.867 n=20}
_{mui-docs - native}
_Errors	_11,405	_11,405	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_3,782,394	_3,782,394	_~	_~	_~	_{p=1.000 n=20}
_Types	_1,355,778	_1,355,778	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{1,678,768k (± 0.09%)}	_{1,678,483k (± 0.09%)}	_~	_1,672,748k	_1,685,181k	_{p=0.947 n=20}
_{Memory Allocs}	_{25,761,228 (± 0.17%)}	_{25,736,476 (± 0.12%)}	_~	_25,592,497	_25,828,339	_{p=0.698 n=20}
_{Config Time}	_{0.009s (± 2.52%)}	_{0.010s (±16.73%)}	_~	_0.008s	_0.024s	_{p=0.510 n=20}
_{Parse Time}	_{0.319s (± 3.00%)}	_{0.319s (± 2.88%)}	_~	_0.287s	_0.375s	_{p=0.723 n=20}
_{Bind Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{3.192s (± 0.91%)}	_{3.207s (± 1.28%)}	_~	_3.056s	_3.381s	_{p=0.507 n=20}
_{Emit Time}	_{0.275s (± 2.99%)}	_{0.272s (± 1.65%)}	_~	_0.258s	_0.296s	_{p=0.825 n=20}
_{Total Time}	_{4.320s (± 0.75%)}	_{4.342s (± 1.05%)}	_~	_4.135s	_4.531s	_{p=0.344 n=20}
_{sentry - native}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_4,793,266	_4,793,266	_~	_~	_~	_{p=1.000 n=20}
_Types	_2,607,066	_2,607,066	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{2,798,859k (± 0.04%)}	_{2,799,561k (± 0.04%)}	_~	_2,796,106k	_2,805,303k	_{p=0.327 n=20}
_{Memory Allocs}	_{75,084,252 (± 0.29%)}	_{75,115,069 (± 0.22%)}	_~	_74,648,555	_75,799,796	_{p=0.495 n=20}
_{Config Time}	_{0.025s (± 0.93%)}	_{0.025s (± 1.11%)}	_~	_0.024s	_0.026s	_{p=1.000 n=20}
_{Parse Time}	_{0.464s (± 4.30%)}	_{0.463s (± 3.76%)}	_~	_0.423s	_0.593s	_{p=0.888 n=20}
_{Bind Time}	_{0.159s (±10.97%)}	_{0.148s (± 9.97%)}	_~	_0.123s	_0.218s	_{p=0.465 n=20}
_{Check Time}	_{6.473s (± 0.58%)}	_{6.503s (± 0.50%)}	_~	_6.392s	_6.624s	_{p=0.144 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{7.172s (± 0.52%)}	_{7.192s (± 0.55%)}	_~	_7.112s	_7.466s	_{p=0.525 n=20}
_{social-app - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_1,883,060	_1,883,060	_~	_~	_~	_{p=1.000 n=20}
_Types	_1,158,093	_1,158,093	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{952,744k (± 0.02%)}	_{952,807k (± 0.02%)}	_~	_951,929k	_953,554k	_{p=0.542 n=20}
_{Memory Allocs}	_{13,493,368 (± 0.12%)}	_{13,524,708 (± 0.33%)}	_~	_13,447,866	_13,802,559	_{p=0.529 n=20}
_{Config Time}	_{0.007s (± 3.00%)}	_{0.007s (± 3.20%)}	_~	_0.007s	_0.008s	_{p=0.514 n=20}
_{Parse Time}	_{0.156s (± 2.72%)}	_{0.154s (± 2.67%)}	_~	_0.137s	_0.174s	_{p=0.506 n=20}
_{Bind Time}	_{0.039s (± 7.75%)}	_{0.041s (±10.57%)}	_~	_0.034s	_0.069s	_{p=0.052 n=20}
_{Check Time}	_{1.388s (± 1.12%)}	_{1.400s (± 1.27%)}	_~	_1.337s	_1.464s	_{p=0.245 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.607s (± 0.95%)}	_{1.622s (± 1.13%)}	_~	_1.562s	_1.700s	_{p=0.185 n=20}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_1,184,972	_1,184,972	_~	_~	_~	_{p=1.000 n=20}
_Types	_438,823	_438,823	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{1,159,636k (± 0.32%)}	_{1,165,366k (± 0.40%)}	_~	_1,150,762k	_1,181,768k	_{p=0.081 n=20}
_{Memory Allocs}	_{47,616,181 (± 0.12%)}	_{47,675,714 (± 0.13%)}	_~	_47,420,041	_47,838,825	_{p=0.142 n=20}
_{Config Time}	_{0.002s (±19.90%)}	_{0.002s (±20.65%)}	_~	_0.001s	_0.003s	_{p=0.346 n=20}
_{Parse Time}	_{0.145s (± 2.63%)}	_{0.143s (± 2.54%)}	_~	_0.131s	_0.157s	_{p=0.596 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.838s (± 1.10%)}	_{0.842s (± 1.48%)}	_~	_0.812s	_0.904s	_{p=0.888 n=20}
_{Emit Time}	_{0.148s (± 2.20%)}	_{0.153s (± 3.81%)}	_~	_0.139s	_0.173s	_{p=0.673 n=20}
_{Total Time}	_{9.811s (± 1.26%)}	_{9.906s (± 1.65%)}	_~	_9.568s	_10.791s	_{p=0.478 n=20}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_263,481	_263,481	_~	_~	_~	_{p=1.000 n=20}
_Types	_196,103	_196,103	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{221,498k (± 0.03%)}	_{221,562k (± 0.02%)}	_~	_221,313k	_221,723k	_{p=0.101 n=20}
_{Memory Allocs}	_{2,388,396 (± 0.01%)}	_{2,388,782 (± 0.01%)}	_~	_2,387,494	_2,390,494	_{p=0.127 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.047s (± 3.92%)}	_{0.047s (± 3.91%)}	_~	_0.043s	_0.056s	_{p=0.682 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.379s (± 0.85%)}	_{0.377s (± 0.80%)}	_~	_0.365s	_0.392s	_{p=0.464 n=20}
_{Emit Time}	_{0.047s (± 5.11%)}	_{0.050s (± 4.50%)}	_~	_0.041s	_0.056s	_{p=0.202 n=20}
_{Total Time}	_{0.502s (± 0.81%)}	_{0.502s (± 0.59%)}	_~	_0.490s	_0.516s	_{p=0.743 n=20}
_{t3code-server - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_4,349,937	_4,349,937	_~	_~	_~	_{p=1.000 n=20}
_Types	_3,042,465	_3,042,465	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{2,394,926k (± 0.02%)}	_{2,395,495k (± 0.02%)}	_~	_2,394,208k	_2,398,366k	_{p=0.122 n=20}
_{Memory Allocs}	_{37,148,050 (± 0.08%)}	_{37,144,725 (± 0.09%)}	_~	_37,068,787	_37,369,167	_{p=0.758 n=20}
_{Config Time}	_0.003s	_0.003s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.248s (± 2.90%)}	_{0.259s (± 6.34%)}	_~	_0.231s	_0.390s	_{p=0.597 n=20}
_{Bind Time}	_{0.101s (±10.83%)}	_{0.093s (±11.03%)}	_~	_0.074s	_0.138s	_{p=0.298 n=20}
_{Check Time}	_{5.981s (± 1.43%)}	_{5.967s (± 0.70%)}	_~	_5.805s	_6.128s	_{p=0.888 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{6.346s (± 1.39%)}	_{6.334s (± 0.88%)}	_~	_6.142s	_6.669s	_{p=0.888 n=20}
_{tanstack-router - native}
_Errors	₁	₁	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_570,149	_570,149	_~	_~	_~	_{p=1.000 n=20}
_Types	_396,551	_396,551	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{315,324k (± 0.01%)}	_{315,286k (± 0.02%)}	_~	_315,097k	_315,476k	_{p=0.265 n=20}
_{Memory Allocs}	_{4,327,102 (± 0.17%)}	_{4,324,629 (± 0.10%)}	_~	_4,314,844	_4,356,290	_{p=0.962 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.041s (± 3.72%)}	_{0.040s (± 3.46%)}	_~	_0.035s	_0.045s	_{p=0.120 n=20}
_{Bind Time}	_{0.011s (± 5.48%)}	_{0.011s (± 6.93%)}	_~	_0.010s	_0.016s	_{p=0.750 n=20}
_{Check Time}	_{0.458s (± 0.67%)}	_{0.457s (± 0.79%)}	_~	_0.446s	_0.475s	_{p=0.357 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.528s (± 0.74%)}	_{0.527s (± 0.87%)}	_~	_0.516s	_0.552s	_{p=0.498 n=20}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_231,607	_231,607	_~	_~	_~	_{p=1.000 n=20}
_Types	_181,163	_181,163	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{190,855k (± 0.02%)}	_{190,885k (± 0.02%)}	_~	_190,721k	_191,010k	_{p=0.176 n=20}
_{Memory Allocs}	_{1,309,997 (± 0.02%)}	_{1,309,997 (± 0.02%)}	_~	_1,309,109	_1,310,937	_{p=0.799 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.040s (± 2.90%)}	_{0.040s (± 2.65%)}	_~	_0.036s	_0.044s	_{p=0.518 n=20}
_{Bind Time}	_{0.020s (± 6.32%)}	_{0.020s (± 5.98%)}	_~	_0.016s	_0.025s	_{p=0.575 n=20}
_{Check Time}	_{0.295s (± 1.56%)}	_{0.293s (± 1.05%)}	_~	_0.281s	_0.305s	_{p=0.973 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.362s (± 1.15%)}	_{0.360s (± 0.75%)}	_~	_0.351s	_0.373s	_{p=0.931 n=20}
_{vscode - native}
_Errors	₁₁	₁₁	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_7,856,949	_7,856,949	_~	_~	_~	_{p=1.000 n=20}
_Types	_4,598,905	_4,598,905	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{5,281,838k (± 0.01%)}	_{5,282,251k (± 0.02%)}	_~	_5,279,264k	_5,286,581k	_{p=0.799 n=20}
_{Memory Allocs}	_{59,204,759 (± 0.02%)}	_{59,207,337 (± 0.02%)}	_~	_59,179,502	_59,281,808	_{p=0.883 n=20}
_{Config Time}	_{0.036s (± 3.44%)}	_{0.037s (± 8.61%)}	_~	_0.034s	_0.066s	_{p=0.653 n=20}
_{Parse Time}	_{1.022s (± 2.70%)}	_{1.019s (± 1.70%)}	_~	_0.969s	_1.116s	_{p=0.995 n=20}
_{Bind Time}	_{0.347s (± 7.59%)}	_{0.337s (± 3.03%)}	_~	_0.313s	_0.412s	_{p=0.784 n=20}
_{Check Time}	_{7.790s (± 0.96%)}	_{7.821s (± 0.64%)}	_~	_7.671s	_8.021s	_{p=0.763 n=20}
_{Emit Time}	_{2.168s (± 6.18%)}	_{2.114s (± 3.42%)}	_~	_2.003s	_2.555s	_{p=0.963 n=20}
_{Total Time}	_{11.427s (± 1.18%)}	_{11.390s (± 0.73%)}	_~	_11.203s	_11.753s	_{p=0.773 n=20}
_{webpack - native}
_Errors	₆₁₅	₆₁₅	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_887,312	_887,312	_~	_~	_~	_{p=1.000 n=20}
_Types	_626,023	_626,023	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{647,555k (± 0.02%)}	_{647,616k (± 0.02%)}	_~	_647,281k	_648,071k	_{p=0.351 n=20}
_{Memory Allocs}	_{6,067,947 (± 0.06%)}	_{6,068,385 (± 0.06%)}	_~	_6,055,390	_6,086,920	_{p=0.925 n=20}
_{Config Time}	_0.004s	_0.004s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.124s (± 2.76%)}	_{0.125s (± 1.43%)}	_~	_0.119s	_0.133s	_{p=0.408 n=20}
_{Bind Time}	_{0.038s (± 7.12%)}	_{0.036s (± 2.70%)}	_~	_0.033s	_0.041s	_{p=0.167 n=20}
_{Check Time}	_{1.012s (± 1.23%)}	_{1.015s (± 0.56%)}	_~	_0.992s	_1.052s	_{p=0.261 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.201s (± 1.06%)}	_{1.201s (± 0.49%)}	_~	_1.179s	_1.236s	_{p=0.234 n=20}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_644,330	_644,330	_~	_~	_~	_{p=1.000 n=20}
_Types	_392,175	_392,175	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{347,005k (± 0.02%)}	_{347,006k (± 0.02%)}	_~	_346,737k	_347,357k	_{p=0.941 n=20}
_{Memory Allocs}	_{3,997,542 (± 0.06%)}	_{4,002,816 (± 0.08%)}	_{+5,274 (+ 0.13%)}	_3,993,293	_4,018,679	_{p=0.010 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.059s (± 2.68%)}	_{0.059s (± 1.94%)}	_~	_0.055s	_0.063s	_{p=0.731 n=20}
_{Bind Time}	_{0.020s (±11.19%)}	_{0.019s (± 9.75%)}	_~	_0.016s	_0.029s	_{p=0.706 n=20}
_{Check Time}	_{0.415s (± 0.65%)}	_{0.414s (± 0.67%)}	_~	_0.405s	_0.426s	_{p=0.448 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.501s (± 0.80%)}	_{0.498s (± 0.74%)}	_~	_0.486s	_0.514s	_{p=0.386 n=20}

System info unknown

Hosts

native

Scenarios

Compiler-Unions - native
angular-1 - native
arktype - native
class-transformer - native
effect - native
mui-docs - native
sentry - native
social-app - native
strada-build-src - native
strada-compiler - native
t3code-server - native
tanstack-router - native
ts-pre-modules - native
vscode - native
webpack - native
xstate-main - native

_Benchmark	_Name	_Iterations
_Current	_pr	₂₀
_Baseline	_baseline	₂₀

Developer Information:

Download Benchmarks

typescript-automation · 2026-11-05T19:12:06Z

Ryan Cavanaugh (@RyanCavanaugh) Here are the results of running the top 400 repos with tsc comparing baseline and pr:

Everything looks good!

Copilot AI balanced review requested due to automatic review settings November 5, 2026 06:54

github-project-automation Bot added this to PR Backlog Nov 5, 2026

github-project-automation Bot moved this to Not started in PR Backlog Nov 5, 2026

typescript-automation Bot added For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Nov 5, 2026

Copilot started reviewing on behalf of Jemmy (JemmyIndex) November 5, 2026 06:55

View session

Copilot AI reviewed Nov 5, 2026

View reviewed changes

Navigation Menu

Repository navigation

fix(parser): allow `in` in array literals in a `for` statement initializer - #65330

fix(parser): allow `in` in array literals in a `for` statement initializer#65330
Jemmy (JemmyIndex) wants to merge 1 commit into
microsoft:mainfrom
JemmyIndex:fix/array-literal-in-for-init

Jemmy (JemmyIndex) commented Nov 5, 2026 •

edited

Loading

Uh oh!

Copilot AI left a comment

Uh oh!

Ryan Cavanaugh (RyanCavanaugh) commented Nov 5, 2026

Uh oh!

typescript-automation Bot commented Nov 5, 2026 •

edited

Loading

Uh oh!

typescript-automation Bot commented Nov 5, 2026

Uh oh!

typescript-automation Bot commented Nov 5, 2026

Uh oh!

typescript-automation Bot commented Nov 5, 2026

tsc

Uh oh!

typescript-automation Bot commented Nov 5, 2026

Uh oh!

This branch has not been deployed

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Conversation

Jemmy (JemmyIndex) commented Nov 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

AI assistance

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🟢 Approval recommended

Uh oh!

Ryan Cavanaugh (RyanCavanaugh) commented Nov 5, 2026

Uh oh!

typescript-automation Bot commented Nov 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

typescript-automation Bot commented Nov 5, 2026

Uh oh!

typescript-automation Bot commented Nov 5, 2026

Uh oh!

typescript-automation Bot commented Nov 5, 2026

tsc

Uh oh!

typescript-automation Bot commented Nov 5, 2026

Uh oh!

This branch has not been deployed

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Jemmy (JemmyIndex) commented Nov 5, 2026 •

edited

Loading

typescript-automation Bot commented Nov 5, 2026 •

edited

Loading