Avoid closure and slice allocations in core helpers and type filtering by jakebailey · Pull Request #65041 · microsoft/TypeScript

Jake Bailey (jakebailey) · 2026-10-29T22:26:28Z

Thanks Steven (@teamchong) for finding these!

When Filter, FilterIndex, or Deduplicate find the first element to drop, they cloned the kept prefix and then grew the result with append. The clone is sized to the prefix only, so any further kept elements trigger one or more reallocations and copies, and the leftover capacity of each abandoned backing array is wasted. The number of remaining elements bounds the result, so allocate that capacity once. For Filter, first skip past any further removed elements: this makes the bound tighter, and when nothing is kept the result is a zero-capacity slice that needs no allocation at all. The case where nothing is removed still returns the input unchanged. Co-authored-by: Steven Chong <[email protected]>

filterType used core.Filter to build the filtered constituent lists of a union and its origin. Those lists are only inputs to union construction, which interns the result and copies the list only when a new union type has to be created; often an existing union is found and the freshly allocated lists are garbage immediately. Scan for the first removed constituent before doing any work, and build both lists in borrowed temporary type sets instead of on the heap. The origin filter also no longer needs a closure wrapping the predicate. removeType on a two-constituent union (such as `T | undefined`, which is very common) now compares the two constituents directly instead of binary searching with CompareTypes. Co-authored-by: Steven Chong <[email protected]>

containsMissingType was stored as a func-valued checker field built from a closure at checker creation. Calls through the field are indirect and cannot be inlined, and the field costs a word per checker. Nothing needs it to be a value, so make it an ordinary method. Co-authored-by: Steven Chong <[email protected]>

structuredTypeRelatedToWorker is one of the hottest functions in the checker, but it built the relateVariances closure on every call, even though only the generic type reference and alias paths use it. The closure also captured and assigned several of the function's locals, which forces them to live in memory for the whole body instead of in registers. Make it a method that receives the state it updates explicitly. The closure also assigned the outer result, but on every path where the caller continues that value is TernaryFalse, which result already holds there. Co-authored-by: Steven Chong <[email protected]>

Jake Bailey (jakebailey) · 2026-10-29T22:26:38Z

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

typescript-automation · 2026-10-29T22:26:43Z

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

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

Copilot

🟢 Approval recommended

No active review issues are blocking the allocation-overhead optimizations.

No open issues 🎉

What changed in this PR

This PR targets allocation overhead in the native TypeScript compiler’s core slice helpers and type checker.

Changes:

Preallocate result capacity in filtering and deduplication helpers.
Replace captured closures with methods for variance comparison and missing-type checks.
Reuse temporary storage for union filtering and add a two-member union removal fast path.

File	Description
`tsc/internal/core/core.go`	Preallocates filtering and deduplication results to avoid repeated slice growth.
`tsc/internal/checker/relater.go`	Extracts variance comparison from a closure into a method.
`tsc/internal/checker/checker.go`	Reuses filtering storage, converts a closure to a method, and optimizes two-member union removal.

_{Review effort: Balanced}

typescript-automation · 2026-10-29T23:27:39Z

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}	_{104,133k (± 0.03%)}	_{104,141k (± 0.03%)}	_~	_104,045k	_104,344k	_{p=0.909 n=20}
_{Memory Allocs}	_{1,263,743 (± 0.01%)}	_{1,250,714 (± 0.01%)}	_{-13,029 (- 1.03%)}	_1,250,201	_1,251,235	_{p=0.000 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.023s (± 3.02%)}	_{0.023s (± 2.16%)}	_~	_0.021s	_0.025s	_{p=0.678 n=20}
_{Bind Time}	_{0.009s (± 6.05%)}	_{0.008s (± 6.07%)}	_~	_0.007s	_0.010s	_{p=0.550 n=20}
_{Check Time}	_{0.215s (± 0.80%)}	_{0.216s (± 1.27%)}	_~	_0.208s	_0.227s	_{p=0.793 n=20}
_{Emit Time}	_{0.140s (± 0.79%)}	_{0.141s (± 1.62%)}	_~	_0.133s	_0.151s	_{p=0.642 n=20}
_{Total Time}	_{0.390s (± 0.53%)}	_{0.392s (± 1.26%)}	_~	_0.380s	_0.413s	_{p=0.888 n=20}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_{586,557 (± 0.02%)}	_{586,501 (± 0.02%)}	_~	_586,098	_586,908	_{p=0.606 n=20}
_Types	_{241,687 (± 0.00%)}	_{241,687 (± 0.00%)}	_~	_241,685	_241,695	_{p=0.539 n=20}
_{Memory Used}	_{517,943k (± 0.02%)}	_{517,966k (± 0.02%)}	_~	_517,680k	_518,439k	_{p=0.718 n=20}
_{Memory Allocs}	_{7,794,468 (± 0.07%)}	_{7,786,045 (± 0.06%)}	_{-8,423 (- 0.11%)}	_7,777,959	_7,810,502	_{p=0.002 n=20}
_{Config Time}	_{0.009s (± 1.15%)}	_{0.009s (± 1.15%)}	_~	_0.009s	_0.010s	_{p=1.000 n=20}
_{Parse Time}	_{0.129s (± 4.41%)}	_{0.126s (± 2.85%)}	_~	_0.113s	_0.139s	_{p=0.653 n=20}
_{Bind Time}	_{0.047s (±11.00%)}	_{0.046s (± 8.84%)}	_~	_0.038s	_0.061s	_{p=0.761 n=20}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=20}
_{Emit Time}	_{0.868s (± 1.15%)}	_{0.869s (± 1.32%)}	_~	_0.835s	_0.940s	_{p=0.973 n=20}
_{Total Time}	_{1.063s (± 1.43%)}	_{1.061s (± 1.22%)}	_~	_1.018s	_1.129s	_{p=0.941 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}	_{497,268k (± 0.01%)}	_{497,302k (± 0.01%)}	_~	_497,092k	_497,517k	_{p=0.402 n=20}
_{Memory Allocs}	_{12,108,443 (± 0.01%)}	_{12,078,586 (± 0.01%)}	_{-29,857 (- 0.25%)}	_12,074,982	_12,082,779	_{p=0.000 n=20}
_{Config Time}	_{0.001s (±18.96%)}	_{0.001s (±20.33%)}	_~	_0.001s	_0.003s	_{p=0.605 n=20}
_{Parse Time}	_{0.049s (± 5.36%)}	_{0.046s (± 3.97%)}	_~	_0.037s	_0.052s	_{p=0.184 n=20}
_{Bind Time}	_{0.016s (±12.33%)}	_{0.016s (±11.23%)}	_~	_0.012s	_0.025s	_{p=0.757 n=20}
_{Check Time}	_{1.091s (± 1.65%)}	_{1.089s (± 2.09%)}	_~	_1.030s	_1.241s	_{p=0.703 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.190s (± 1.60%)}	_{1.184s (± 2.04%)}	_~	_1.121s	_1.339s	_{p=0.417 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}	_{27,836k (± 0.01%)}	_{27,840k (± 0.02%)}	_~	_27,813k	_27,871k	_{p=0.343 n=20}
_{Memory Allocs}	_{248,575 (± 0.05%)}	_{248,703 (± 0.06%)}	_~	_248,129	_249,220	_{p=0.114 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.012s (± 3.30%)}	_{0.012s (± 2.44%)}	_~	_0.010s	_0.012s	_{p=0.696 n=20}
_{Bind Time}	_{0.003s (± 8.18%)}	_{0.004s (±11.84%)}	_~	_0.003s	_0.005s	_{p=1.000 n=20}
_{Check Time}	_{0.008s (± 4.43%)}	_{0.008s (± 4.84%)}	_~	_0.007s	_0.010s	_{p=0.767 n=20}
_{Emit Time}	_{0.008s (± 7.26%)}	_{0.008s (± 5.88%)}	_~	_0.007s	_0.010s	_{p=0.968 n=20}
_{Total Time}	_{0.032s (± 1.74%)}	_{0.032s (± 1.45%)}	_~	_0.030s	_0.033s	_{p=0.729 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}	_{940,486k (± 0.02%)}	_{940,750k (± 0.02%)}	_{+264k (+ 0.03%)}	_939,973k	_941,584k	_{p=0.049 n=20}
_{Memory Allocs}	_{12,674,375 (± 0.03%)}	_{12,638,668 (± 0.02%)}	_{-35,708 (- 0.28%)}	_12,632,049	_12,647,883	_{p=0.000 n=20}
_{Config Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.146s (± 1.85%)}	_{0.149s (± 1.18%)}	_~	_0.142s	_0.155s	_{p=0.171 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.929s (± 0.79%)}	_{0.943s (± 2.58%)}	_~	_0.911s	_1.159s	_{p=0.425 n=20}
_{Emit Time}	_{0.502s (± 2.12%)}	_{0.502s (± 1.67%)}	_~	_0.469s	_0.537s	_{p=0.836 n=20}
_{Total Time}	_{1.676s (± 0.63%)}	_{1.687s (± 1.29%)}	_~	_1.649s	_1.870s	_{p=0.578 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	_1,355,974	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{1,836,020k (± 0.07%)}	_{1,835,358k (± 0.08%)}	_~	_1,830,609k	_1,840,737k	_{p=0.529 n=20}
_{Memory Allocs}	_{25,988,051 (± 0.10%)}	_{25,268,290 (± 0.13%)}	_{-719,761 (- 2.77%)}	_25,159,679	_25,421,096	_{p=0.000 n=20}
_{Config Time}	_{0.009s (± 1.17%)}	_0.009s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.309s (± 1.80%)}	_{0.307s (± 2.17%)}	_~	_0.280s	_0.330s	_{p=0.836 n=20}
_{Bind Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{3.231s (± 0.67%)}	_{3.215s (± 0.64%)}	_~	_3.153s	_3.305s	_{p=0.095 n=20}
_{Emit Time}	_{0.253s (± 1.06%)}	_{0.252s (± 0.95%)}	_~	_0.243s	_0.260s	_{p=0.673 n=20}
_{Total Time}	_{4.316s (± 0.52%)}	_{4.301s (± 0.48%)}	_~	_4.228s	_4.380s	_{p=0.176 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	_2,607,045	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{2,880,758k (± 0.03%)}	_{2,880,107k (± 0.04%)}	_~	_2,878,189k	_2,888,777k	_{p=0.091 n=20}
_{Memory Allocs}	_{75,387,553 (± 0.32%)}	_{74,504,553 (± 0.23%)}	_{-883,000 (- 1.17%)}	_74,019,927	_75,353,339	_{p=0.000 n=20}
_{Config Time}	_{0.025s (± 0.93%)}	_{0.025s (± 0.84%)}	_~	_0.024s	_0.025s	_{p=0.731 n=20}
_{Parse Time}	_{0.490s (± 6.11%)}	_{0.499s (± 6.47%)}	_~	_0.430s	_0.651s	_{p=0.794 n=20}
_{Bind Time}	_{0.166s (±10.73%)}	_{0.177s (±11.03%)}	_~	_0.133s	_0.242s	_{p=0.596 n=20}
_{Check Time}	_{6.766s (± 0.83%)}	_{6.743s (± 0.47%)}	_~	_6.611s	_6.875s	_{p=0.836 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{7.497s (± 0.83%)}	_{7.497s (± 0.47%)}	_~	_7.358s	_7.633s	_{p=0.516 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}	_{972,398k (± 0.01%)}	_{972,270k (± 0.01%)}	_~	_971,314k	_972,741k	_{p=0.274 n=20}
_{Memory Allocs}	_{13,570,270 (± 0.28%)}	_{13,518,857 (± 0.13%)}	_{-51,413 (- 0.38%)}	_13,473,994	_13,629,248	_{p=0.001 n=20}
_{Config Time}	_{0.007s (± 1.48%)}	_{0.007s (± 2.39%)}	_~	_0.007s	_0.008s	_{p=0.605 n=20}
_{Parse Time}	_{0.154s (± 1.77%)}	_{0.156s (± 2.14%)}	_~	_0.144s	_0.174s	_{p=0.408 n=20}
_{Bind Time}	_{0.043s (± 8.03%)}	_{0.046s (± 8.25%)}	_~	_0.038s	_0.063s	_{p=0.172 n=20}
_{Check Time}	_{1.476s (± 0.76%)}	_{1.465s (± 0.76%)}	_~	_1.421s	_1.508s	_{p=0.116 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.696s (± 0.69%)}	_{1.693s (± 0.67%)}	_~	_1.661s	_1.751s	_{p=0.441 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}	_{1,164,121k (± 0.21%)}	_{1,164,754k (± 0.33%)}	_~	_1,153,208k	_1,181,525k	_{p=0.862 n=20}
_{Memory Allocs}	_{47,656,437 (± 0.11%)}	_{47,319,936 (± 0.11%)}	_{-336,502 (- 0.71%)}	_47,135,118	_47,518,192	_{p=0.000 n=20}
_{Config Time}	_{0.002s (±14.66%)}	_{0.002s (±10.98%)}	_~	_0.001s	_0.003s	_{p=0.387 n=20}
_{Parse Time}	_{0.140s (± 1.61%)}	_{0.139s (± 1.27%)}	_~	_0.133s	_0.149s	_{p=0.682 n=20}
_{Bind Time}	_{0.000s (±208.60%)}	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.811s (± 0.34%)}	_{0.811s (± 0.54%)}	_~	_0.795s	_0.836s	_{p=0.888 n=20}
_{Emit Time}	_{0.140s (± 1.18%)}	_{0.139s (± 0.97%)}	_~	_0.130s	_0.142s	_{p=0.909 n=20}
_{Total Time}	_{9.414s (± 0.37%)}	_{9.408s (± 0.45%)}	_~	_9.290s	_9.678s	_{p=0.723 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}	_{224,603k (± 0.02%)}	_{224,588k (± 0.02%)}	_~	_224,428k	_224,739k	_{p=0.473 n=20}
_{Memory Allocs}	_{2,401,195 (± 0.01%)}	_{2,378,690 (± 0.02%)}	_{-22,506 (- 0.94%)}	_2,376,363	_2,379,709	_{p=0.000 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.052s (± 3.35%)}	_{0.053s (± 3.29%)}	_~	_0.047s	_0.059s	_{p=0.209 n=20}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Check Time}	_{0.406s (± 0.83%)}	_{0.403s (± 0.69%)}	_{-0.003s (- 0.85%)}	_0.388s	_0.418s	_{p=0.038 n=20}
_{Emit Time}	_{0.051s (± 5.41%)}	_{0.053s (± 5.55%)}	_~	_0.043s	_0.063s	_{p=0.238 n=20}
_{Total Time}	_{0.539s (± 0.85%)}	_{0.541s (± 0.90%)}	_~	_0.518s	_0.558s	_{p=0.482 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}	_{2,433,440k (± 0.02%)}	_{2,433,691k (± 0.03%)}	_~	_2,432,246k	_2,436,496k	_{p=0.758 n=20}
_{Memory Allocs}	_{37,406,243 (± 0.09%)}	_{37,232,546 (± 0.06%)}	_{-173,698 (- 0.46%)}	_37,171,106	_37,349,464	_{p=0.000 n=20}
_{Config Time}	_0.003s	_0.003s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.255s (± 2.03%)}	_{0.255s (± 2.15%)}	_~	_0.235s	_0.278s	_{p=0.888 n=20}
_{Bind Time}	_{0.090s (±10.25%)}	_{0.085s (±10.15%)}	_~	_0.074s	_0.137s	_{p=0.080 n=20}
_{Check Time}	_{7.233s (± 0.44%)}	_{7.214s (± 0.49%)}	_~	_7.122s	_7.400s	_{p=0.324 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{7.592s (± 0.36%)}	_{7.567s (± 0.44%)}	_~	_7.476s	_7.752s	_{p=0.119 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}	_{331,430k (± 0.02%)}	_{331,423k (± 0.01%)}	_~	_331,247k	_331,621k	_{p=0.899 n=20}
_{Memory Allocs}	_{4,395,836 (± 0.19%)}	_{4,399,931 (± 0.28%)}	_~	_4,374,543	_4,471,611	_{p=0.989 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.041s (± 7.27%)}	_{0.039s (± 2.69%)}	_~	_0.035s	_0.043s	_{p=0.276 n=20}
_{Bind Time}	_{0.017s (±49.01%)}	_{0.014s (±10.78%)}	_~	_0.011s	_0.021s	_{p=0.358 n=20}
_{Check Time}	_{0.566s (± 3.54%)}	_{0.570s (± 3.51%)}	_~	_0.549s	_0.747s	_{p=0.291 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.643s (± 4.73%)}	_{0.642s (± 3.12%)}	_~	_0.618s	_0.819s	_{p=0.401 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}	_{193,539k (± 0.01%)}	_{193,524k (± 0.01%)}	_~	_193,456k	_193,581k	_{p=0.616 n=20}
_{Memory Allocs}	_{1,318,162 (± 0.02%)}	_{1,298,375 (± 0.03%)}	_{-19,787 (- 1.50%)}	_1,296,898	_1,299,988	_{p=0.000 n=20}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.045s (± 3.15%)}	_{0.044s (± 2.45%)}	_~	_0.041s	_0.048s	_{p=0.311 n=20}
_{Bind Time}	_{0.021s (± 4.78%)}	_{0.021s (± 5.44%)}	_~	_0.017s	_0.026s	_{p=0.751 n=20}
_{Check Time}	_{0.295s (± 1.17%)}	_{0.293s (± 0.93%)}	_~	_0.283s	_0.302s	_{p=0.424 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.366s (± 0.72%)}	_{0.364s (± 0.65%)}	_~	_0.356s	_0.375s	_{p=0.207 n=20}
_{vscode - native}
_Errors	₁₁	₁₁	_~	_~	_~	_{p=1.000 n=20}
_Symbols	_7,469,251	_7,469,251	_~	_~	_~	_{p=1.000 n=20}
_Types	_4,370,893	_4,370,893	_~	_~	_~	_{p=1.000 n=20}
_{Memory Used}	_{5,194,058k (± 0.02%)}	_{5,193,510k (± 0.02%)}	_~	_5,190,978k	_5,197,389k	_{p=0.355 n=20}
_{Memory Allocs}	_{56,759,098 (± 0.02%)}	_{56,517,675 (± 0.03%)}	_{-241,422 (- 0.43%)}	_56,492,220	_56,608,033	_{p=0.000 n=20}
_{Config Time}	_{0.035s (± 0.95%)}	_{0.035s (± 0.54%)}	_~	_0.035s	_0.036s	_{p=1.000 n=20}
_{Parse Time}	_{0.905s (± 1.39%)}	_{0.913s (± 1.84%)}	_~	_0.819s	_0.988s	_{p=0.410 n=20}
_{Bind Time}	_{0.317s (± 9.31%)}	_{0.302s (± 3.98%)}	_~	_0.286s	_0.406s	_{p=0.454 n=20}
_{Check Time}	_{7.535s (± 1.35%)}	_{7.508s (± 0.56%)}	_~	_7.261s	_7.666s	_{p=0.805 n=20}
_{Emit Time}	_{2.739s (± 4.70%)}	_{2.740s (± 4.77%)}	_~	_2.551s	_3.551s	_{p=0.279 n=20}
_{Total Time}	_{11.587s (± 1.27%)}	_{11.556s (± 1.01%)}	_~	_11.317s	_12.257s	_{p=0.984 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}	_{693,499k (± 0.01%)}	_{693,421k (± 0.01%)}	_~	_693,180k	_693,691k	_{p=0.144 n=20}
_{Memory Allocs}	_{6,498,571 (± 0.03%)}	_{6,461,761 (± 0.04%)}	_{-36,810 (- 0.57%)}	_6,457,115	_6,474,616	_{p=0.000 n=20}
_{Config Time}	_0.004s	_0.004s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.146s (± 2.92%)}	_{0.144s (± 3.45%)}	_~	_0.125s	_0.158s	_{p=0.654 n=20}
_{Bind Time}	_{0.047s (± 9.43%)}	_{0.043s (± 7.77%)}	_~	_0.038s	_0.063s	_{p=0.078 n=20}
_{Check Time}	_{1.133s (± 0.82%)}	_{1.139s (± 0.69%)}	_~	_1.109s	_1.167s	_{p=0.344 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{1.354s (± 0.85%)}	_{1.352s (± 0.65%)}	_~	_1.322s	_1.387s	_{p=0.825 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}	_{350,984k (± 0.03%)}	_{350,972k (± 0.02%)}	_~	_350,768k	_351,368k	_{p=0.846 n=20}
_{Memory Allocs}	_{3,992,272 (± 0.08%)}	_{3,989,652 (± 0.08%)}	_~	_3,978,692	_4,001,543	_{p=0.183 n=20}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=20}
_{Parse Time}	_{0.059s (± 2.65%)}	_{0.059s (± 2.43%)}	_~	_0.055s	_0.066s	_{p=0.742 n=20}
_{Bind Time}	_{0.020s (± 8.15%)}	_{0.020s (±10.49%)}	_~	_0.017s	_0.031s	_{p=0.820 n=20}
_{Check Time}	_{0.413s (± 0.85%)}	_{0.411s (± 0.60%)}	_~	_0.402s	_0.425s	_{p=0.285 n=20}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=20}
_{Total Time}	_{0.498s (± 0.73%)}	_{0.496s (± 0.75%)}	_~	_0.487s	_0.518s	_{p=0.317 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 15:02

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

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

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

typescript-automation Bot assigned Jake Bailey (jakebailey) 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 22:27

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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 closure and slice allocations in core helpers and type filtering - #65041

Avoid closure and slice allocations in core helpers and type filtering#65041
Jake Bailey (jakebailey) wants to merge 4 commits into
microsoft:mainfrom
jakebailey:perf/core-helpers

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