Avoid allocations and redundant work when checking calls and object literals by jakebailey · Pull Request #65040 · microsoft/TypeScript

Jake Bailey (jakebailey) · 2026-10-29T22:26:10Z

Thanks Steven (@teamchong) for finding these!

checkGrammarObjectLiteralExpression allocated a fresh map for every object literal it checked, even though most literals have zero or one property and so can never contain duplicate names, and the map is discarded as soon as the check returns. Only use a map when duplicates are possible (two or more properties outside of destructuring), and take it from a small per-checker free list so that repeated checks reuse the same backing storage. Nested object literals checked while computing property names take their own map from the list, so reentrancy is safe. Unusually large maps are not retained, since Go maps never shrink. Co-authored-by: Steven Chong <[email protected]>

checkExpressionForMutableLocation first asks isConstContext, which for literal-like expressions computes the expression's contextual type to see whether it is a const type parameter. When the answer is no, it then immediately computed the very same contextual type again to widen the literal. getContextualType walks up the tree and may consult resolved signatures, so doing it twice for every literal in a mutable location is wasted work. Let an internal variant of isConstContext hand back the contextual type it computed when that type alone decided the result, and use it for the widening step instead of recomputing it. When the answer came from an enclosing node instead, the type is recomputed as before. Co-authored-by: Steven Chong <[email protected]>

checkObjectLiteral eagerly allocated two symbol tables per literal: one for the properties of the literal type, and, under strictNullChecks, one collecting every property to detect properties that a later spread always overwrites. The latter is only ever consulted when the literal contains a spread, which most literals do not. Spreads also flush the current properties into the spread type and replace the table with a fresh one that frequently ends up unused, for instance when the spread is the last element. Allocate the overwrite-tracking table only when the literal contains a spread, and create the properties table on first use. Also skip mapType when remapping the final spread type if it is not a union, since there is only the type itself to inspect. Co-authored-by: Steven Chong <[email protected]>

Every call resolution allocated a fresh slice for its reordered candidate signatures, even though the list is only used while that resolution is in progress (unless signature help asks for it). Call resolution is one of the hottest paths in the checker, and most calls have a single candidate, for which the general reordering loop with its symbol lookups and slice insertions is unnecessary. Keep a small per-checker free list of candidate slices: a resolution takes one, and gives it back when it returns. Nested resolutions started while checking arguments take their own slice from the list, so they never share storage with an outer resolution in progress. Lists handed out through candidatesOutArray are never reused. Zero and one signatures skip the reordering logic entirely, as there is nothing to reorder. Co-authored-by: Steven Chong <[email protected]>

Jake Bailey (jakebailey) · 2026-10-29T22:26:22Z

TypeScript Bot (@typescript-bot) perf test this faster

typescript-automation · 2026-10-29T22:26:27Z

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

Command	Status	Results
`perf test this faster`	✅ Started	👀 Results

Copilot

🟡 Changes recommended

The popped pool slot is not cleared, allowing the backing array to retain oversized maps and their property-name strings despite the retention limit.

1 open issue

Clear popped slot to prevent oversized map retention · New

What changed in this PR

This PR reduces allocations and repeated work in the native TypeScript checker when checking calls and object literals.

Changes:

Reuse temporary candidate lists and duplicate-property maps.
Create object-literal symbol tables lazily and bypass unnecessary type mapping.
Reuse contextual types computed during const-context checks.

File	Description
`tsc/internal/checker/grammarchecks.go`	Pools duplicate-property maps and skips allocation when duplicate checks are unnecessary.
`tsc/internal/checker/checker.go`	Reuses call-candidate storage and reduces object-literal allocation and contextual-type work.

_{Review effort: Balanced}

A popped entry stayed reachable from the free list's backing array until it was overwritten. If the borrowed value then grew too large to be returned to the pool, the stale slot kept it alive anyway, defeating the retention limit.

Copilot

🟢 Approval recommended

No active review issues remain for the checker allocation and reuse optimizations.

No open issues 🎉

1 resolved since last review

Clear popped slot to prevent oversized map retention

_{Review effort: Balanced}

typescript-automation · 2026-10-29T23:17:17Z

Jake Bailey (@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 - 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}	_{104,145k (± 0.03%)}	_{104,345k (± 0.03%)}	_{+200k (+ 0.19%)}	_104,208k	_104,445k	_{p=0.000 n=20}
_{Memory Allocs}	_{1,263,768 (± 0.01%)}	_{1,238,386 (± 0.01%)}	_{-25,382 (- 2.01%)}	_1,237,783	_1,238,832	_{p=0.000 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.023s (± 2.70%)}	_{0.023s (± 2.09%)}	_~	_0.021s	_0.025s	_{p=0.105 n=20}
_{Bind Time}	_{0.008s (± 6.37%)}	_{0.008s (± 5.34%)}	_~	_0.007s	_0.010s	_{p=0.599 n=20}
_{Check Time}	_{0.212s (± 0.62%)}	_{0.211s (± 0.72%)}	_~	_0.205s	_0.218s	_{p=0.494 n=20}
_{Emit Time}	_{0.136s (± 0.67%)}	_{0.137s (± 1.03%)}	_~	_0.132s	_0.147s	_{p=0.120 n=20}
_{Total Time}	_{0.382s (± 0.34%)}	_{0.384s (± 0.65%)}	_~	_0.374s	_0.400s	_{p=0.289 n=20}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_{586,512 (± 0.01%)}	_{586,525 (± 0.01%)}	_~	_586,249	_586,834	_{p=0.616 n=20}
_Types	_{241,688 (± 0.00%)}	_{241,688 (± 0.00%)}	_~	_241,683	_241,697	_{p=0.396 n=20}
_{Memory Used}	_{517,898k (± 0.02%)}	_{517,958k (± 0.02%)}	_~	_517,584k	_518,323k	_{p=0.369 n=20}
_{Memory Allocs}	_{7,801,167 (± 0.11%)}	_{7,738,926 (± 0.10%)}	_{-62,241 (- 0.80%)}	_7,726,654	_7,789,713	_{p=0.000 n=20}
_{Config Time}	_0.009s	_0.009s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.133s (± 3.66%)}	_{0.133s (± 4.21%)}	_~	_0.119s	_0.159s	_{p=0.856 n=20}
_{Bind Time}	_{0.041s (± 8.00%)}	_{0.045s (± 9.78%)}	_~	_0.037s	_0.069s	_{p=0.162 n=20}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=20}
_{Emit Time}	_{0.846s (± 0.83%)}	_{0.855s (± 1.34%)}	_~	_0.827s	_0.927s	_{p=0.365 n=20}
_{Total Time}	_{1.039s (± 1.14%)}	_{1.053s (± 1.70%)}	_~	_1.013s	_1.156s	_{p=0.379 n=20}
_{arktype - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_685,920	_685,920	_~	_~	_~	_{p=1.000 n=20}
_Types	_939,467	_939,467	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{497,291k (± 0.01%)}	_{497,299k (± 0.01%)}	_~	_497,163k	_497,562k	_{p=0.578 n=20}
_{Memory Allocs}	_{12,108,020 (± 0.01%)}	_{12,073,505 (± 0.02%)}	_{-34,514 (- 0.29%)}	_12,068,485	_12,084,589	_{p=0.000 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.042s (± 3.82%)}	_{0.042s (± 3.67%)}	_~	_0.036s	_0.047s	_{p=0.855 n=20}
_{Bind Time}	_{0.013s (±10.16%)}	_{0.013s (± 7.54%)}	_~	_0.011s	_0.018s	_{p=0.817 n=20}
_{Check Time}	_{0.974s (± 0.66%)}	_{0.981s (± 0.68%)}	_~	_0.948s	_1.012s	_{p=0.112 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.059s (± 0.62%)}	_{1.065s (± 0.59%)}	_~	_1.036s	_1.101s	_{p=0.167 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}	_{27,838k (± 0.02%)}	_{27,840k (± 0.01%)}	_~	_27,826k	_27,858k	_{p=0.440 n=20}
_{Memory Allocs}	_{248,693 (± 0.05%)}	_{245,635 (± 0.05%)}	_{-3,058 (- 1.23%)}	_245,279	_246,252	_{p=0.000 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.011s (± 5.26%)}	_{0.011s (± 5.36%)}	_~	_0.009s	_0.013s	_{p=0.628 n=20}
_{Bind Time}	_{0.004s (±11.18%)}	_{0.003s (± 3.54%)}	_{🟩-0.001s (-19.18%)}	_0.002s	_0.003s	_{p=0.000 n=20}
_{Check Time}	_{0.008s (± 5.55%)}	_{0.008s (± 4.54%)}	_~	_0.007s	_0.010s	_{p=0.075 n=20}
_{Emit Time}	_{0.009s (± 5.07%)}	_{0.008s (± 5.14%)}	_{🟩-0.001s (- 9.55%)}	_0.007s	_0.009s	_{p=0.008 n=20}
_{Total Time}	_{0.032s (± 3.08%)}	_{0.031s (± 2.12%)}	_~	_0.029s	_0.033s	_{p=0.140 n=20}
_{effect - native}
_Errors	₁₂	₁₂	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_1,235,115	_1,235,115	_~	_~	_~	_{p=1.000 n=20}
_Types	_894,113	_894,113	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{940,629k (± 0.02%)}	_{940,579k (± 0.02%)}	_~	_939,791k	_941,198k	_{p=0.846 n=20}
_{Memory Allocs}	_{12,678,412 (± 0.07%)}	_{12,581,167 (± 0.02%)}	_{-97,245 (- 0.77%)}	_12,573,226	_12,594,441	_{p=0.000 n=20}
_{Config Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.148s (± 1.52%)}	_{0.147s (± 1.48%)}	_~	_0.138s	_0.153s	_{p=1.000 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.936s (± 0.68%)}	_{0.937s (± 0.78%)}	_~	_0.906s	_0.967s	_{p=0.963 n=20}
_{Emit Time}	_{0.507s (± 1.51%)}	_{0.504s (± 1.74%)}	_~	_0.459s	_0.530s	_{p=0.713 n=20}
_{Total Time}	_{1.688s (± 0.46%)}	_{1.684s (± 0.54%)}	_~	_1.629s	_1.726s	_{p=0.533 n=20}
_{mui-docs - native}
_Errors	_11,405	_11,405	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_3,784,019	_3,784,019	_~	_~	_~	_{p=1.000 n=20}
_Types	_1,355,974	_1,355,973	_{-1 (- 0.00%)}	_~	_~	_{p=0.000 n=20}
_{Memory Used}	_{1,837,615k (± 0.11%)}	_{1,837,386k (± 0.07%)}	_~	_1,832,330k	_1,843,934k	_{p=0.602 n=20}
_{Memory Allocs}	_{26,012,739 (± 0.08%)}	_{25,833,004 (± 0.11%)}	_{-179,736 (- 0.69%)}	_25,755,903	_25,984,823	_{p=0.000 n=20}
_{Config Time}	_{0.008s (± 1.77%)}	_{0.008s (± 2.10%)}	_~	_0.008s	_0.009s	_{p=1.000 n=20}
_{Parse Time}	_{0.294s (± 2.45%)}	_{0.285s (± 1.56%)}	_~	_0.262s	_0.300s	_{p=0.051 n=20}
_{Bind Time}	_{0.001s (± 9.93%)}	_{0.001s (±18.96%)}	_~	_0.001s	_0.003s	_{p=1.000 n=20}
_{Check Time}	_{3.068s (± 0.77%)}	_{3.085s (± 1.13%)}	_~	_3.016s	_3.300s	_{p=0.723 n=20}
_{Emit Time}	_{0.238s (± 1.39%)}	_{0.241s (± 1.40%)}	_~	_0.231s	_0.262s	_{p=0.343 n=20}
_{Total Time}	_{4.104s (± 0.90%)}	_{4.105s (± 1.02%)}	_~	_4.022s	_4.362s	_{p=0.683 n=20}
_{sentry - native}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_4,793,245	_4,793,245	_~	_~	_~	_{p=1.000 n=20}
_Types	_2,607,045	_2,603,266	_{-3,779 (- 0.14%)}	_~	_~	_{p=0.000 n=20}
_{Memory Used}	_{2,881,448k (± 0.04%)}	_{2,880,472k (± 0.03%)}	_~	_2,878,406k	_2,884,691k	_{p=0.157 n=20}
_{Memory Allocs}	_{75,436,799 (± 0.33%)}	_{74,384,514 (± 0.18%)}	_{-1,052,285 (- 1.39%)}	_74,009,508	_75,370,029	_{p=0.000 n=20}
_{Config Time}	_{0.025s (± 1.03%)}	_{0.025s (± 0.58%)}	_~	_0.024s	_0.025s	_{p=0.826 n=20}
_{Parse Time}	_{0.484s (± 2.90%)}	_{0.486s (± 4.10%)}	_~	_0.431s	_0.601s	_{p=0.743 n=20}
_{Bind Time}	_{0.163s (± 9.27%)}	_{0.166s (± 9.55%)}	_~	_0.140s	_0.250s	_{p=0.488 n=20}
_{Check Time}	_{6.862s (± 0.52%)}	_{6.882s (± 0.64%)}	_~	_6.744s	_7.102s	_{p=0.507 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{7.584s (± 0.44%)}	_{7.611s (± 0.51%)}	_~	_7.481s	_7.781s	_{p=0.324 n=20}
_{social-app - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_1,883,074	_1,883,074	_~	_~	_~	_{p=1.000 n=20}
_Types	_1,158,168	_1,158,168	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{972,381k (± 0.02%)}	_{972,355k (± 0.01%)}	_~	_971,932k	_972,745k	_{p=0.784 n=20}
_{Memory Allocs}	_{13,587,000 (± 0.24%)}	_{13,462,592 (± 0.29%)}	_{-124,408 (- 0.92%)}	_13,384,306	_13,725,284	_{p=0.000 n=20}
_{Config Time}	_{0.008s (± 3.84%)}	_{0.008s (± 4.89%)}	_~	_0.008s	_0.011s	_{p=0.605 n=20}
_{Parse Time}	_{0.175s (± 1.98%)}	_{0.178s (± 3.95%)}	_~	_0.162s	_0.229s	_{p=0.878 n=20}
_{Bind Time}	_{0.046s (± 7.60%)}	_{0.049s (±10.12%)}	_~	_0.040s	_0.075s	_{p=0.438 n=20}
_{Check Time}	_{1.565s (± 0.67%)}	_{1.554s (± 0.77%)}	_~	_1.508s	_1.616s	_{p=0.167 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.813s (± 0.73%)}	_{1.808s (± 0.63%)}	_~	_1.774s	_1.860s	_{p=0.569 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	_438,963	_438,963	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{1,166,611k (± 0.31%)}	_{1,167,217k (± 0.34%)}	_~	_1,155,060k	_1,183,344k	_{p=0.947 n=20}
_{Memory Allocs}	_{47,679,814 (± 0.09%)}	_{46,666,261 (± 0.14%)}	_{-1,013,553 (- 2.13%)}	_46,467,610	_46,909,485	_{p=0.000 n=20}
_{Config Time}	_{0.002s (±15.67%)}	_{0.002s (±19.90%)}	_~	_0.000s	_0.003s	_{p=0.602 n=20}
_{Parse Time}	_{0.149s (± 5.09%)}	_{0.147s (± 4.24%)}	_~	_0.132s	_0.194s	_{p=0.568 n=20}
_{Bind Time}	_0.000s	_{0.000s (±208.60%)}	_~	_0.000s	_0.004s	_{p=1.000 n=20}
_{Check Time}	_{0.840s (± 0.87%)}	_{0.850s (± 1.25%)}	_~	_0.816s	_0.902s	_{p=0.140 n=20}
_{Emit Time}	_{0.146s (± 3.36%)}	_{0.149s (± 3.02%)}	_~	_0.138s	_0.170s	_{p=0.364 n=20}
_{Total Time}	_{9.807s (± 0.94%)}	_{9.884s (± 1.36%)}	_~	_9.491s	_10.849s	_{p=0.383 n=20}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_263,511	_263,511	_~	_~	_~	_{p=1.000 n=20}
_Types	_196,116	_196,116	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{224,576k (± 0.02%)}	_{224,664k (± 0.02%)}	_{+88k (+ 0.04%)}	_224,507k	_224,937k	_{p=0.044 n=20}
_{Memory Allocs}	_{2,401,186 (± 0.01%)}	_{2,338,191 (± 0.01%)}	_{-62,995 (- 2.62%)}	_2,337,032	_2,339,286	_{p=0.000 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.054s (± 2.91%)}	_{0.053s (± 3.30%)}	_~	_0.046s	_0.061s	_{p=0.691 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.411s (± 1.23%)}	_{0.406s (± 0.55%)}	_~	_0.399s	_0.417s	_{p=0.416 n=20}
_{Emit Time}	_{0.050s (± 5.76%)}	_{0.049s (± 5.19%)}	_~	_0.043s	_0.058s	_{p=0.466 n=20}
_{Total Time}	_{0.545s (± 1.01%)}	_{0.538s (± 0.76%)}	_{-0.007s (- 1.28%)}	_0.524s	_0.557s	_{p=0.043 n=20}
_{t3code-server - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_4,350,661	_4,350,661	_~	_~	_~	_{p=1.000 n=20}
_Types	_3,040,644	_3,040,644	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{2,434,099k (± 0.02%)}	_{2,434,017k (± 0.03%)}	_~	_2,431,855k	_2,436,846k	_{p=0.678 n=20}
_{Memory Allocs}	_{37,398,619 (± 0.17%)}	_{36,780,166 (± 0.10%)}	_{-618,454 (- 1.65%)}	_36,685,276	_37,045,923	_{p=0.000 n=20}
_{Config Time}	_0.003s	_0.003s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.259s (± 2.37%)}	_{0.259s (± 2.35%)}	_~	_0.231s	_0.286s	_{p=0.732 n=20}
_{Bind Time}	_{0.087s (± 7.35%)}	_{0.089s (± 9.60%)}	_~	_0.076s	_0.140s	_{p=0.783 n=20}
_{Check Time}	_{7.877s (± 1.33%)}	_{7.832s (± 0.77%)}	_~	_7.629s	_8.152s	_{p=0.774 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{8.239s (± 1.33%)}	_{8.194s (± 0.77%)}	_~	_7.978s	_8.512s	_{p=0.805 n=20}
_{tanstack-router - native}
_Errors	₁	₁	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_571,756	_571,756	_~	_~	_~	_{p=1.000 n=20}
_Types	_397,689	_397,689	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{331,398k (± 0.01%)}	_{331,444k (± 0.02%)}	_~	_331,245k	_331,647k	_{p=0.176 n=20}
_{Memory Allocs}	_{4,388,891 (± 0.12%)}	_{4,338,471 (± 0.14%)}	_{-50,420 (- 1.15%)}	_4,323,822	_4,367,198	_{p=0.000 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.040s (± 3.24%)}	_{0.040s (± 3.25%)}	_~	_0.036s	_0.046s	_{p=0.453 n=20}
_{Bind Time}	_{0.012s (± 7.70%)}	_{0.012s (± 9.72%)}	_~	_0.010s	_0.020s	_{p=0.657 n=20}
_{Check Time}	_{0.555s (± 0.73%)}	_{0.555s (± 0.60%)}	_~	_0.543s	_0.568s	_{p=0.794 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.626s (± 0.77%)}	_{0.627s (± 0.59%)}	_~	_0.614s	_0.641s	_{p=0.490 n=20}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_231,616	_231,616	_~	_~	_~	_{p=1.000 n=20}
_Types	_181,195	_181,195	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{193,535k (± 0.02%)}	_{193,562k (± 0.01%)}	_~	_193,479k	_193,659k	_{p=0.159 n=20}
_{Memory Allocs}	_{1,318,107 (± 0.01%)}	_{1,263,904 (± 0.02%)}	_{🟩-54,203 (- 4.11%)}	_1,262,917	_1,264,880	_{p=0.000 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.047s (± 2.32%)}	_{0.047s (± 4.39%)}	_~	_0.041s	_0.061s	_{p=0.887 n=20}
_{Bind Time}	_{0.022s (± 6.28%)}	_{0.023s (± 7.46%)}	_~	_0.018s	_0.035s	_{p=0.941 n=20}
_{Check Time}	_{0.334s (± 2.88%)}	_{0.333s (± 2.05%)}	_~	_0.305s	_0.354s	_{p=0.867 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.410s (± 2.65%)}	_{0.410s (± 1.90%)}	_~	_0.381s	_0.432s	_{p=0.794 n=20}
_{vscode - native}
_Errors	₁₁	₁₁	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_7,475,710	_7,475,710	_~	_~	_~	_{p=1.000 n=20}
_Types	_4,374,355	_4,374,355	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{5,193,347k (± 0.02%)}	_{5,192,694k (± 0.02%)}	_~	_5,190,355k	_5,195,582k	_{p=0.277 n=20}
_{Memory Allocs}	_{56,787,891 (± 0.03%)}	_{54,347,561 (± 0.03%)}	_{🟩-2,440,330 (- 4.30%)}	_54,323,708	_54,453,606	_{p=0.000 n=20}
_{Config Time}	_{0.037s (± 1.34%)}	_{0.037s (± 1.56%)}	_~	_0.035s	_0.040s	_{p=0.995 n=20}
_{Parse Time}	_{0.929s (± 1.62%)}	_{0.936s (± 2.27%)}	_~	_0.830s	_1.002s	_{p=0.298 n=20}
_{Bind Time}	_{0.322s (± 1.73%)}	_{0.335s (± 5.37%)}	_~	_0.297s	_0.445s	_{p=0.433 n=20}
_{Check Time}	_{8.041s (± 1.11%)}	_{8.025s (± 1.16%)}	_~	_7.597s	_8.442s	_{p=0.989 n=20}
_{Emit Time}	_{2.792s (± 4.25%)}	_{2.796s (± 4.74%)}	_~	_2.620s	_3.615s	_{p=0.753 n=20}
_{Total Time}	_{12.180s (± 1.13%)}	_{12.188s (± 1.08%)}	_~	_11.811s	_12.715s	_{p=0.947 n=20}
_{webpack - native}
_Errors	₆₁₆	₆₁₆	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_917,188	_917,188	_~	_~	_~	_{p=1.000 n=20}
_Types	_636,859	_636,859	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{693,543k (± 0.01%)}	_{693,466k (± 0.02%)}	_~	_693,077k	_694,124k	_{p=0.229 n=20}
_{Memory Allocs}	_{6,501,930 (± 0.05%)}	_{6,381,866 (± 0.06%)}	_{-120,064 (- 1.85%)}	_6,371,003	_6,402,666	_{p=0.000 n=20}
_{Config Time}	_0.004s	_0.004s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.140s (± 4.16%)}	_{0.140s (± 3.29%)}	_~	_0.126s	_0.155s	_{p=0.804 n=20}
_{Bind Time}	_{0.050s (±12.80%)}	_{0.042s (± 5.63%)}	_~	_0.037s	_0.057s	_{p=0.191 n=20}
_{Check Time}	_{1.124s (± 0.53%)}	_{1.126s (± 0.63%)}	_~	_1.102s	_1.175s	_{p=0.703 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.341s (± 0.71%)}	_{1.335s (± 0.49%)}	_~	_1.312s	_1.367s	_{p=0.402 n=20}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_640,490	_640,490	_~	_~	_~	_{p=1.000 n=20}
_Types	_387,984	_387,984	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{350,974k (± 0.02%)}	_{350,926k (± 0.02%)}	_~	_350,775k	_351,279k	_{p=0.398 n=20}
_{Memory Allocs}	_{3,994,874 (± 0.07%)}	_{3,915,109 (± 0.08%)}	_{-79,766 (- 2.00%)}	_3,902,674	_3,927,651	_{p=0.000 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.059s (± 2.35%)}	_{0.060s (± 2.66%)}	_~	_0.056s	_0.067s	_{p=0.220 n=20}
_{Bind Time}	_{0.021s (± 9.73%)}	_{0.020s (±11.18%)}	_~	_0.017s	_0.034s	_{p=0.685 n=20}
_{Check Time}	_{0.415s (± 0.78%)}	_{0.415s (± 0.95%)}	_~	_0.402s	_0.434s	_{p=0.931 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.500s (± 0.91%)}	_{0.502s (± 0.99%)}	_~	_0.484s	_0.520s	_{p=0.625 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:

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Jake Bailey (jakebailey) and others added 4 commits October 29, 2026 15:00

Copilot AI balanced review requested due to automatic review settings October 29, 2026 22:26

github-project-automation Bot added this to PR Backlog Oct 29, 2026

typescript-automation Bot assigned Jake Bailey (jakebailey) Oct 29, 2026

github-project-automation Bot moved this to Not started in PR Backlog Oct 29, 2026

typescript-automation Bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Oct 29, 2026

Copilot started reviewing on behalf of Jake Bailey (jakebailey) October 29, 2026 22:26

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Comment thread tsc/internal/checker/grammarchecks.go

Clear popped slots in the checker's free lists

df81007

A popped entry stayed reachable from the free list's backing array until it was overwritten. If the borrowed value then grew too large to be returned to the pool, the stale slot kept it alive anyway, defeating the retention limit.

Jake Bailey (jakebailey) requested a balanced review from Copilot October 29, 2026 22:48

Copilot started reviewing on behalf of Jake Bailey (jakebailey) October 29, 2026 22:48

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Jake Bailey (jakebailey) added the Domain: Performance Reports of unusually slow behavior label Oct 29, 2026

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Avoid allocations and redundant work when checking calls and object literals - #65040

Avoid allocations and redundant work when checking calls and object literals#65040
Jake Bailey (jakebailey) wants to merge 5 commits into
microsoft:mainfrom
jakebailey:perf/expression-checking

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