Count intersection property names with a plain map and slice by jakebailey · Pull Request #64876 · microsoft/TypeScript

Jake Bailey (jakebailey) · 2026-10-19T18:45:55Z

                  │   old.txt   │             new.txt              │
                  │   sec/op    │   sec/op    vs base              │
Tsc/bluesky          2.430 ± 2%   2.383 ± 3%       ~ (p=0.180 n=6)
Tsc/sentry          10.044 ± 1%   9.931 ± 2%       ~ (p=0.180 n=6)
Tsc/t3code-server    8.038 ± 1%   7.904 ± 2%  -1.67% (p=0.026 n=6)
Tsc/mui-docs         6.518 ± 2%   6.138 ± 3%  -5.83% (p=0.002 n=6)
geomean              5.980        5.821       -2.66%

                  │   old.txt    │              new.txt               │
                  │    rss-B     │    rss-B      vs base              │
Tsc/bluesky         1.189Gi ± 3%   1.176Gi ± 4%       ~ (p=0.485 n=6)
Tsc/sentry          3.271Gi ± 4%   3.215Gi ± 6%       ~ (p=0.240 n=6)
Tsc/t3code-server   2.753Gi ± 5%   2.776Gi ± 6%       ~ (p=0.937 n=6)
Tsc/mui-docs        2.362Gi ± 7%   2.314Gi ± 5%       ~ (p=0.699 n=6)
geomean             2.242Gi        2.220Gi       -0.99%

                  │   old.txt    │              new.txt               │
                  │    heap-B    │    heap-B     vs base              │
Tsc/bluesky         915.2Mi ± 0%   914.9Mi ± 0%       ~ (p=0.699 n=6)
Tsc/sentry          2.483Gi ± 0%   2.482Gi ± 0%       ~ (p=0.818 n=6)
Tsc/t3code-server   2.179Gi ± 0%   2.180Gi ± 0%       ~ (p=0.394 n=6)
Tsc/mui-docs        1.732Gi ± 0%   1.732Gi ± 0%       ~ (p=0.310 n=6)
geomean             1.701Gi        1.701Gi       -0.00%

This will conflict with #64815 to some extent

Jake Bailey (jakebailey) · 2026-10-19T18:46:04Z

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

typescript-automation · 2026-10-19T18:46:10Z

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

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

Copilot

🟢 Approval recommended

Static review found no blocking issues in this localized refactor; automated validation was not run.

1 open issue

Update PR description to match the map-based implementation · New

What changed in this PR

Optimizes property counting when the checker determines whether an intersection reduces to never, while preserving first-occurrence order.

Changes:

Replaces the ordered map with a name-to-index map and count slice.
Skips lookups for the first constituent’s properties.
Updates counting and workspace-reuse tests.

File	Description
tsc/internal/checker/utilities.go	Implements map-and-slice property counts.
tsc/internal/checker/types_test.go	Adapts counting and reuse assertions.
tsc/internal/checker/checker.go	Uses the new counting operations during intersection reduction.

_{Review effort: Balanced}

+	entries []propertyCount
+	indices map[string]int32


typescript-automation · 2026-10-19T19:14:50Z

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=12}
_Symbols	_115,276	_115,276	_~	_~	_~	_{p=1.000 n=12}
_Types	_79,613	_79,613	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{113,611k (± 0.07%)}	_{113,461k (± 0.04%)}	_{-150k (- 0.13%)}	_113,372k	_113,611k	_{p=0.003 n=12}
_{Memory Allocs}	_{2,212,588 (± 0.00%)}	_{2,212,505 (± 0.01%)}	_~	_2,212,245	_2,212,961	_{p=0.266 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.039s (± 4.10%)}	_{0.040s (± 3.57%)}	_~	_0.037s	_0.044s	_{p=0.480 n=12}
_{Bind Time}	_{0.014s (± 9.58%)}	_{0.014s (± 8.31%)}	_~	_0.011s	_0.017s	_{p=0.830 n=12}
_{Check Time}	_{0.467s (± 0.82%)}	_{0.471s (± 0.64%)}	_~	_0.465s	_0.480s	_{p=0.070 n=12}
_{Emit Time}	_{0.275s (± 2.12%)}	_{0.269s (± 2.63%)}	_~	_0.253s	_0.285s	_{p=0.247 n=12}
_{Total Time}	_{0.802s (± 0.95%)}	_{0.800s (± 0.82%)}	_~	_0.787s	_0.818s	_{p=0.681 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{847,269 (± 0.06%)}	_{847,364 (± 0.08%)}	_~	_845,490	_849,037	_{p=0.843 n=12}
_Types	_{247,031 (± 0.00%)}	_{247,035 (± 0.00%)}	_{+3 (+ 0.00%)}	_247,029	_247,045	_{p=0.016 n=12}
_{Memory Used}	_{596,362k (± 0.02%)}	_{596,381k (± 0.03%)}	_~	_595,851k	_596,863k	_{p=0.799 n=12}
_{Memory Allocs}	_{13,139,205 (± 0.03%)}	_{13,148,114 (± 0.07%)}	_~	_13,134,175	_13,175,783	_{p=0.078 n=12}
_{Config Time}	_{0.017s (± 1.45%)}	_{0.017s (± 1.70%)}	_~	_0.016s	_0.017s	_{p=1.000 n=12}
_{Parse Time}	_{0.221s (± 1.77%)}	_{0.228s (± 2.77%)}	_~	_0.214s	_0.242s	_{p=0.091 n=12}
_{Bind Time}	_{0.081s (±11.65%)}	_{0.074s (±15.34%)}	_~	_0.058s	_0.102s	_{p=0.213 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.561s (± 1.37%)}	_{1.577s (± 1.32%)}	_~	_1.532s	_1.647s	_{p=0.325 n=12}
_{Total Time}	_{1.902s (± 1.39%)}	_{1.916s (± 1.04%)}	_~	_1.880s	_1.971s	_{p=0.434 n=12}
_{mui-docs - native}
_Errors	_11,405	_11,405	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_4,331,983	_4,331,983	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,370,520	_1,370,520	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{2,624,694k (± 0.03%)}	_{2,626,152k (± 0.05%)}	_~	_2,622,356k	_2,629,755k	_{p=0.052 n=12}
_{Memory Allocs}	_{27,713,795 (± 0.08%)}	_{27,713,469 (± 0.05%)}	_~	_27,661,441	_27,738,171	_{p=0.671 n=12}
_{Config Time}	_{0.017s (± 1.70%)}	_{0.017s (± 1.45%)}	_~	_0.016s	_0.017s	_{p=1.000 n=12}
_{Parse Time}	_{0.466s (± 3.53%)}	_{0.478s (± 3.09%)}	_~	_0.440s	_0.513s	_{p=0.202 n=12}
_{Bind Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{7.222s (± 0.13%)}	_{6.973s (± 0.62%)}	_{🟩-0.249s (- 3.45%)}	_6.855s	_7.125s	_{p=0.000 n=12}
_{Emit Time}	_{0.566s (±11.48%)}	_{0.524s (±13.72%)}	_~	_0.417s	_0.661s	_{p=0.352 n=12}
_{Total Time}	_{9.012s (± 0.82%)}	_{8.726s (± 1.21%)}	_{🟩-0.286s (- 3.17%)}	_8.532s	_8.929s	_{p=0.000 n=12}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,388,680	_1,388,680	_~	_~	_~	_{p=1.000 n=12}
_Types	_441,862	_441,862	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,311,304k (± 0.49%)}	_{1,316,572k (± 0.55%)}	_~	_1,300,268k	_1,343,645k	_{p=0.143 n=12}
_{Memory Allocs}	_{78,204,684 (± 0.14%)}	_{78,244,813 (± 0.10%)}	_~	_77,942,738	_78,401,237	_{p=0.671 n=12}
_{Config Time}	_{0.003s (±12.31%)}	_{0.003s (± 9.48%)}	_~	_0.003s	_0.004s	_{p=1.000 n=12}
_{Parse Time}	_{0.255s (± 2.42%)}	_{0.251s (± 1.44%)}	_~	_0.242s	_0.260s	_{p=0.181 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.679s (± 0.46%)}	_{1.675s (± 0.52%)}	_~	_1.648s	_1.696s	_{p=0.451 n=12}
_{Emit Time}	_{0.290s (± 3.30%)}	_{0.304s (± 3.61%)}	_{🔻+0.015s (+ 5.06%)}	_0.286s	_0.345s	_{p=0.027 n=12}
_{Total Time}	_{19.823s (± 0.63%)}	_{19.908s (± 0.71%)}	_~	_19.415s	_20.223s	_{p=0.319 n=12}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_334,953	_334,953	_~	_~	_~	_{p=1.000 n=12}
_Types	_197,616	_197,616	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{247,491k (± 0.04%)}	_{247,503k (± 0.02%)}	_~	_247,424k	_247,698k	_{p=1.000 n=12}
_{Memory Allocs}	_{4,329,337 (± 0.01%)}	_{4,330,004 (± 0.01%)}	_{+667 (+ 0.02%)}	_4,328,447	_4,330,998	_{p=0.045 n=12}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.112s (± 4.22%)}	_{0.114s (± 4.07%)}	_~	_0.099s	_0.124s	_{p=0.400 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{0.965s (± 0.58%)}	_{0.968s (± 0.74%)}	_~	_0.954s	_0.985s	_{p=0.284 n=12}
_{Emit Time}	_{0.146s (± 3.46%)}	_{0.154s (± 4.88%)}	_~	_0.134s	_0.170s	_{p=0.070 n=12}
_{Total Time}	_{1.276s (± 0.74%)}	_{1.294s (± 0.85%)}	_{+0.018s (+ 1.41%)}	_1.271s	_1.322s	_{p=0.027 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_303,834	_303,834	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,663	_181,663	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{215,252k (± 0.02%)}	_{215,226k (± 0.02%)}	_~	_215,082k	_215,331k	_{p=0.272 n=12}
_{Memory Allocs}	_{1,401,488 (± 0.02%)}	_{1,401,793 (± 0.01%)}	_~	_1,401,399	_1,402,406	_{p=0.052 n=12}
_{Config Time}	_0.000s	_{0.000s (±146.91%)}	_~	_0.000s	_0.001s	_{p=0.478 n=12}
_{Parse Time}	_{0.097s (± 3.48%)}	_{0.098s (± 2.60%)}	_~	_0.093s	_0.105s	_{p=0.467 n=12}
_{Bind Time}	_{0.043s (± 6.32%)}	_{0.042s (± 7.29%)}	_~	_0.032s	_0.051s	_{p=0.639 n=12}
_{Check Time}	_{0.745s (± 0.86%)}	_{0.746s (± 0.57%)}	_~	_0.734s	_0.757s	_{p=0.898 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.900s (± 0.90%)}	_{0.902s (± 0.62%)}	_~	_0.889s	_0.918s	_{p=0.504 n=12}
_{vscode - native}
_Errors	₃₉₆	₃₉₆	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_12,501,426	_12,501,426	_~	_~	_~	_{p=1.000 n=12}
_Types	_4,091,299	_4,091,299	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{5,843,208k (± 0.01%)}	_{5,843,893k (± 0.02%)}	_~	_5,841,588k	_5,846,890k	_{p=0.242 n=12}
_{Memory Allocs}	_{59,416,904 (± 0.01%)}	_{59,424,090 (± 0.02%)}	_~	_59,410,476	_59,471,687	_{p=0.078 n=12}
_{Config Time}	_{0.076s (± 0.48%)}	_{0.076s (± 0.24%)}	_~	_0.076s	_0.077s	_{p=0.590 n=12}
_{Parse Time}	_{1.826s (± 2.06%)}	_{1.803s (± 2.00%)}	_~	_1.742s	_1.906s	_{p=0.434 n=12}
_{Bind Time}	_{0.641s (±13.90%)}	_{0.712s (±12.79%)}	_~	_0.527s	_0.923s	_{p=0.198 n=12}
_{Check Time}	_{14.703s (± 0.95%)}	_{14.583s (± 0.99%)}	_{-0.119s (- 0.81%)}	_14.330s	_14.847s	_{p=0.050 n=12}
_{Emit Time}	_{5.322s (± 6.90%)}	_{5.266s (± 6.37%)}	_~	_4.502s	_5.920s	_{p=0.713 n=12}
_{Total Time}	_{22.653s (± 1.32%)}	_{22.531s (± 1.05%)}	_~	_21.993s	_22.995s	_{p=0.590 n=12}
_{webpack - native}
_Errors	₅₉₈	₅₉₈	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,398,302	_1,398,302	_~	_~	_~	_{p=1.000 n=12}
_Types	_670,900	_670,900	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{885,544k (± 0.02%)}	_{885,710k (± 0.02%)}	_~	_885,190k	_885,997k	_{p=0.114 n=12}
_{Memory Allocs}	_{6,928,895 (± 0.04%)}	_{6,928,483 (± 0.03%)}	_~	_6,924,793	_6,936,985	_{p=0.799 n=12}
_{Config Time}	_0.009s	_0.009s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.317s (± 2.37%)}	_{0.322s (± 3.67%)}	_~	_0.295s	_0.349s	_{p=0.451 n=12}
_{Bind Time}	_{0.079s (± 7.54%)}	_{0.077s (± 3.36%)}	_~	_0.070s	_0.085s	_{p=1.000 n=12}
_{Check Time}	_{2.968s (± 0.25%)}	_{2.965s (± 0.50%)}	_~	_2.934s	_3.012s	_{p=0.486 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{3.412s (± 0.33%)}	_{3.411s (± 0.45%)}	_~	_3.364s	_3.445s	_{p=0.989 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,060,810	_1,060,810	_~	_~	_~	_{p=1.000 n=12}
_Types	_389,671	_389,671	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{471,880k (± 0.02%)}	_{471,904k (± 0.02%)}	_~	_471,677k	_472,246k	_{p=0.671 n=12}
_{Memory Allocs}	_{4,221,665 (± 0.10%)}	_{4,222,310 (± 0.08%)}	_~	_4,210,454	_4,229,639	_{p=0.755 n=12}
_{Config Time}	_0.003s	_{0.003s (± 8.64%)}	_~	_0.002s	_0.003s	_{p=0.478 n=12}
_{Parse Time}	_{0.134s (± 3.56%)}	_{0.140s (± 2.86%)}	_~	_0.125s	_0.148s	_{p=0.085 n=12}
_{Bind Time}	_{0.045s (±12.71%)}	_{0.044s (±17.39%)}	_~	_0.033s	_0.065s	_{p=0.527 n=12}
_{Check Time}	_{1.093s (± 0.99%)}	_{1.092s (± 0.93%)}	_~	_1.070s	_1.119s	_{p=0.921 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.285s (± 0.86%)}	_{1.287s (± 1.01%)}	_~	_1.251s	_1.316s	_{p=0.989 n=12}

System info unknown

Hosts

native

Scenarios

Compiler-Unions - native
angular-1 - native
mui-docs - native
strada-build-src - native
strada-compiler - native
ts-pre-modules - native
vscode - native
webpack - native
xstate-main - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

Developer Information:

Download Benchmarks

Deciding whether an intersection reduces to never counts how many constituents declare each property name. The ordered map used for this is a general-purpose structure that does more bookkeeping per operation than this hot path needs, and each property costs a lookup and an assignment. On mui-docs this shows up as a few percent of single-checker time. Count into a slice of entries indexed by a plain string map instead. The slice keeps first-occurrence order for the reduction check, and the first constituent's names are inserted without a lookup since property names are already unique within a type. │ old │ new │ │ sec/op │ sec/op vs base │ Tsc/bluesky 3.179 ± 1% 3.133 ± 1% -1.45% (p=0.039 n=6) Tsc/sentry 12.90 ± 7% 12.77 ± 17% ~ (p=0.818 n=6) Tsc/t3code-server 16.85 ± 3% 16.80 ± 3% ~ (p=0.937 n=6) Tsc/mui-docs 8.536 ± 3% 8.152 ± 1% -4.50% (p=0.002 n=6) geomean 8.763 8.604 -1.81% │ old │ new │ │ rss-B │ rss-B vs base │ Tsc/bluesky 1.439Gi ± 2% 1.417Gi ± 1% ~ (p=0.093 n=6) Tsc/sentry 4.566Gi ± 4% 4.504Gi ± 4% ~ (p=0.937 n=6) Tsc/t3code-server 4.488Gi ± 5% 4.344Gi ± 9% ~ (p=0.485 n=6) Tsc/mui-docs 3.535Gi ± 4% 3.391Gi ± 4% ~ (p=0.065 n=6) geomean 3.195Gi 3.114Gi -2.55% │ old │ new │ │ heap-B │ heap-B vs base │ Tsc/bluesky 1.153Gi ± 0% 1.152Gi ± 0% ~ (p=0.394 n=6) Tsc/sentry 3.620Gi ± 0% 3.622Gi ± 0% ~ (p=0.485 n=6) Tsc/t3code-server 3.761Gi ± 0% 3.762Gi ± 0% ~ (p=0.310 n=6) Tsc/mui-docs 2.641Gi ± 0% 2.641Gi ± 0% ~ (p=0.818 n=6) geomean 2.537Gi 2.537Gi +0.01%

Jake Bailey (jakebailey) · 2026-10-25T00:02:47Z

TypeScript Bot (@typescript-bot) perf test

typescript-automation · 2026-10-25T00:02:54Z

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

Command	Status	Results
`perf test`	✅ Started	👀 Results

typescript-automation · 2026-10-25T00:36:07Z

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=12}
_Symbols	_88,466	_88,466	_~	_~	_~	_{p=1.000 n=12}
_Types	_79,607	_79,607	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{109,266k (± 0.07%)}	_{109,206k (± 0.06%)}	_~	_109,078k	_109,363k	_{p=0.266 n=12}
_{Memory Allocs}	_{2,196,729 (± 0.00%)}	_{2,196,699 (± 0.01%)}	_~	_2,196,350	_2,197,251	_{p=0.340 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.049s (± 3.45%)}	_{0.047s (± 4.65%)}	_~	_0.042s	_0.054s	_{p=0.101 n=12}
_{Bind Time}	_{0.017s (±10.09%)}	_{0.017s (±10.59%)}	_~	_0.013s	_0.021s	_{p=0.919 n=12}
_{Check Time}	_{0.575s (± 0.79%)}	_{0.578s (± 0.61%)}	_~	_0.569s	_0.584s	_{p=0.223 n=12}
_{Emit Time}	_{0.323s (± 2.74%)}	_{0.326s (± 2.66%)}	_~	_0.304s	_0.349s	_{p=0.619 n=12}
_{Total Time}	_{0.972s (± 1.15%)}	_{0.976s (± 1.08%)}	_~	_0.947s	_1.001s	_{p=0.560 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{586,539 (± 0.01%)}	_{586,410 (± 0.03%)}	_~	_586,027	_586,782	_{p=0.192 n=12}
_Types	_{241,692 (± 0.00%)}	_{241,692 (± 0.00%)}	_~	_241,690	_241,695	_{p=0.928 n=12}
_{Memory Used}	_{551,134k (± 0.02%)}	_{551,231k (± 0.02%)}	_~	_550,902k	_551,564k	_{p=0.235 n=12}
_{Memory Allocs}	_{13,081,109 (± 0.10%)}	_{13,080,376 (± 0.08%)}	_~	_13,068,372	_13,112,138	_{p=0.932 n=12}
_{Config Time}	_{0.020s (± 0.90%)}	_{0.020s (± 1.21%)}	_~	_0.020s	_0.021s	_{p=1.000 n=12}
_{Parse Time}	_{0.280s (± 3.21%)}	_{0.281s (± 2.93%)}	_~	_0.268s	_0.310s	_{p=0.810 n=12}
_{Bind Time}	_{0.097s (±15.97%)}	_{0.101s (±13.27%)}	_~	_0.071s	_0.137s	_{p=0.876 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.800s (± 1.62%)}	_{1.808s (± 1.60%)}	_~	_1.733s	_1.862s	_{p=0.600 n=12}
_{Total Time}	_{2.218s (± 1.66%)}	_{2.232s (± 1.46%)}	_~	_2.144s	_2.295s	_{p=0.451 n=12}
_{arktype - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_685,943	_685,943	_~	_~	_~	_{p=1.000 n=12}
_Types	_939,490	_939,490	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{533,170k (± 0.01%)}	_{533,256k (± 0.01%)}	_~	_533,157k	_533,385k	_{p=0.062 n=12}
_{Memory Allocs}	_{12,771,698 (± 0.02%)}	_{12,771,931 (± 0.02%)}	_~	_12,768,729	_12,777,870	_{p=0.713 n=12}
_{Config Time}	_0.003s	_0.003s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.090s (± 4.32%)}	_{0.089s (± 3.52%)}	_~	_0.082s	_0.096s	_{p=0.853 n=12}
_{Bind Time}	_{0.025s (± 3.96%)}	_{0.026s (±10.67%)}	_~	_0.023s	_0.036s	_{p=0.594 n=12}
_{Check Time}	_{2.160s (± 0.55%)}	_{2.145s (± 0.68%)}	_~	_2.099s	_2.183s	_{p=0.124 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{2.338s (± 0.22%)}	_{2.321s (± 0.39%)}	_{-0.018s (- 0.75%)}	_2.296s	_2.346s	_{p=0.002 n=12}
_{mui-docs - native}
_Errors	_11,405	_11,405	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_3,784,027	_3,784,027	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,355,982	_1,355,982	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{2,200,472k (± 0.07%)}	_{2,199,877k (± 0.08%)}	_~	_2,194,421k	_2,204,607k	_{p=0.551 n=12}
_{Memory Allocs}	_{26,472,718 (± 0.06%)}	_{26,453,182 (± 0.06%)}	_~	_26,409,362	_26,498,155	_{p=0.114 n=12}
_{Config Time}	_{0.020s (± 0.90%)}	_{0.020s (± 1.40%)}	_~	_0.020s	_0.021s	_{p=0.590 n=12}
_{Parse Time}	_{0.587s (± 3.79%)}	_{0.585s (± 2.74%)}	_~	_0.554s	_0.640s	_{p=0.311 n=12}
_{Bind Time}	_{0.003s (±10.34%)}	_{0.003s (±10.34%)}	_~	_0.002s	_0.003s	_{p=1.000 n=12}
_{Check Time}	_{7.087s (± 0.40%)}	_{6.825s (± 0.54%)}	_{🟩-0.262s (- 3.70%)}	_6.773s	_6.931s	_{p=0.000 n=12}
_{Emit Time}	_{0.584s (± 5.51%)}	_{0.566s (± 2.82%)}	_~	_0.506s	_0.593s	_{p=0.876 n=12}
_{Total Time}	_{9.213s (± 0.52%)}	_{8.931s (± 0.42%)}	_{🟩-0.282s (- 3.07%)}	_8.871s	_9.062s	_{p=0.000 n=12}
_{sentry - native}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_4,793,249	_4,793,249	_~	_~	_~	_{p=1.000 n=12}
_Types	_2,607,051	_2,607,051	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{3,207,233k (± 0.02%)}	_{3,207,541k (± 0.06%)}	_~	_3,204,688k	_3,214,180k	_{p=0.590 n=12}
_{Memory Allocs}	_{75,231,191 (± 0.07%)}	_{75,262,252 (± 0.08%)}	_~	_75,131,495	_75,430,407	_{p=0.347 n=12}
_{Config Time}	_{0.060s (± 0.54%)}	_{0.060s (± 0.41%)}	_~	_0.060s	_0.061s	_{p=0.193 n=12}
_{Parse Time}	_{1.016s (± 2.13%)}	_{1.002s (± 2.79%)}	_~	_0.939s	_1.065s	_{p=0.701 n=12}
_{Bind Time}	_{0.288s (±13.25%)}	_{0.349s (±13.95%)}	_~	_0.262s	_0.451s	_{p=0.061 n=12}
_{Check Time}	_{13.648s (± 0.63%)}	_{13.658s (± 0.65%)}	_~	_13.462s	_13.942s	_{p=0.989 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{15.083s (± 0.66%)}	_{15.142s (± 0.70%)}	_~	_14.965s	_15.540s	_{p=0.620 n=12}
_{social-app - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,883,075	_1,883,075	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,158,171	_1,158,171	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,057,496k (± 0.01%)}	_{1,057,581k (± 0.01%)}	_~	_1,057,269k	_1,058,001k	_{p=0.514 n=12}
_{Memory Allocs}	_{13,572,364 (± 0.17%)}	_{13,575,144 (± 0.21%)}	_~	_13,527,219	_13,682,457	_{p=0.932 n=12}
_{Config Time}	_{0.017s (± 1.65%)}	_{0.017s (± 1.65%)}	_~	_0.017s	_0.018s	_{p=1.000 n=12}
_{Parse Time}	_{0.355s (± 1.69%)}	_{0.353s (± 1.48%)}	_~	_0.340s	_0.368s	_{p=0.639 n=12}
_{Bind Time}	_{0.079s (± 5.67%)}	_{0.078s (± 8.40%)}	_~	_0.069s	_0.108s	_{p=0.415 n=12}
_{Check Time}	_{3.310s (± 0.55%)}	_{3.291s (± 0.56%)}	_~	_3.218s	_3.324s	_{p=0.103 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{3.784s (± 0.38%)}	_{3.761s (± 0.32%)}	_{-0.023s (- 0.60%)}	_3.734s	_3.798s	_{p=0.015 n=12}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,184,976	_1,184,976	_~	_~	_~	_{p=1.000 n=12}
_Types	_438,967	_438,967	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,281,690k (± 0.77%)}	_{1,271,199k (± 0.35%)}	_~	_1,258,503k	_1,286,606k	_{p=0.089 n=12}
_{Memory Allocs}	_{77,391,918 (± 0.10%)}	_{77,410,275 (± 0.10%)}	_~	_77,094,617	_77,574,716	_{p=0.887 n=12}
_{Config Time}	_{0.004s (±12.60%)}	_{0.004s (± 7.33%)}	_~	_0.004s	_0.005s	_{p=0.562 n=12}
_{Parse Time}	_{0.305s (± 2.07%)}	_{0.308s (± 2.22%)}	_~	_0.289s	_0.332s	_{p=0.354 n=12}
_{Bind Time}	_{0.000s (±217.90%)}	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.951s (± 0.51%)}	_{1.950s (± 0.49%)}	_~	_1.931s	_1.975s	_{p=0.580 n=12}
_{Emit Time}	_{0.382s (± 4.33%)}	_{0.367s (± 4.14%)}	_~	_0.326s	_0.392s	_{p=0.385 n=12}
_{Total Time}	_{23.526s (± 0.63%)}	_{23.484s (± 0.86%)}	_~	_22.760s	_23.845s	_{p=0.887 n=12}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_263,513	_263,513	_~	_~	_~	_{p=1.000 n=12}
_Types	_196,118	_196,118	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{236,006k (± 0.04%)}	_{236,072k (± 0.02%)}	_~	_235,936k	_236,224k	_{p=0.147 n=12}
_{Memory Allocs}	_{4,286,993 (± 0.01%)}	_{4,287,324 (± 0.01%)}	_~	_4,285,893	_4,288,589	_{p=0.266 n=12}
_{Config Time}	_{0.000s (±146.91%)}	_{0.000s (±77.74%)}	_~	_0.000s	_0.001s	_{p=0.371 n=12}
_{Parse Time}	_{0.093s (± 4.81%)}	_{0.090s (± 4.25%)}	_~	_0.082s	_0.100s	_{p=0.353 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{0.788s (± 0.70%)}	_{0.785s (± 0.52%)}	_~	_0.777s	_0.799s	_{p=0.258 n=12}
_{Emit Time}	_{0.118s (± 5.08%)}	_{0.119s (± 4.29%)}	_~	_0.106s	_0.131s	_{p=0.809 n=12}
_{Total Time}	_{1.044s (± 0.46%)}	_{1.038s (± 0.86%)}	_~	_1.013s	_1.058s	_{p=0.202 n=12}
_{t3code-server - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_4,350,705	_4,350,705	_~	_~	_~	_{p=1.000 n=12}
_Types	_3,040,691	_3,040,691	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{2,610,812k (± 0.02%)}	_{2,610,771k (± 0.03%)}	_~	_2,609,346k	_2,614,828k	_{p=0.347 n=12}
_{Memory Allocs}	_{37,341,072 (± 0.07%)}	_{37,335,859 (± 0.05%)}	_~	_37,274,645	_37,385,380	_{p=0.671 n=12}
_{Config Time}	_0.005s	_0.005s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.450s (± 2.22%)}	_{0.449s (± 2.43%)}	_~	_0.420s	_0.476s	_{p=0.966 n=12}
_{Bind Time}	_{0.143s (±16.63%)}	_{0.141s (±12.44%)}	_~	_0.115s	_0.188s	_{p=0.921 n=12}
_{Check Time}	_{13.661s (± 0.15%)}	_{13.657s (± 0.36%)}	_~	_13.574s	_13.828s	_{p=0.486 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{14.272s (± 0.09%)}	_{14.270s (± 0.32%)}	_~	_14.191s	_14.432s	_{p=0.744 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_231,617	_231,617	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,196	_181,196	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{203,527k (± 0.02%)}	_{203,515k (± 0.02%)}	_~	_203,390k	_203,572k	_{p=0.600 n=12}
_{Memory Allocs}	_{1,358,561 (± 0.02%)}	_{1,358,292 (± 0.02%)}	_~	_1,357,726	_1,358,832	_{p=0.060 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.079s (± 3.27%)}	_{0.079s (± 3.79%)}	_~	_0.071s	_0.086s	_{p=0.920 n=12}
_{Bind Time}	_{0.035s (± 9.61%)}	_{0.031s (±10.30%)}	_~	_0.024s	_0.039s	_{p=0.138 n=12}
_{Check Time}	_{0.604s (± 0.86%)}	_{0.605s (± 1.04%)}	_~	_0.592s	_0.624s	_{p=0.745 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.730s (± 0.55%)}	_{0.730s (± 0.61%)}	_~	_0.718s	_0.744s	_{p=0.701 n=12}
_{vscode - native}
_Errors	₁₀	₁₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_7,175,632	_7,175,632	_~	_~	_~	_{p=1.000 n=12}
_Types	_4,223,910	_4,223,910	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{5,354,720k (± 0.02%)}	_{5,354,738k (± 0.01%)}	_~	_5,352,733k	_5,356,467k	_{p=0.932 n=12}
_{Memory Allocs}	_{61,910,140 (± 0.01%)}	_{61,905,880 (± 0.01%)}	_~	_61,900,158	_61,918,701	_{p=0.671 n=12}
_{Config Time}	_{0.078s (± 0.54%)}	_{0.078s (± 0.31%)}	_~	_0.078s	_0.079s	_{p=1.000 n=12}
_{Parse Time}	_{1.956s (± 2.48%)}	_{1.953s (± 2.19%)}	_~	_1.833s	_2.054s	_{p=0.854 n=12}
_{Bind Time}	_{0.700s (±15.21%)}	_{0.677s (±13.84%)}	_~	_0.547s	_1.001s	_{p=0.682 n=12}
_{Check Time}	_{16.999s (± 0.65%)}	_{17.023s (± 0.65%)}	_~	_16.791s	_17.373s	_{p=0.682 n=12}
_{Emit Time}	_{5.611s (± 8.83%)}	_{5.630s (± 8.15%)}	_~	_5.034s	_6.704s	_{p=0.767 n=12}
_{Total Time}	_{25.428s (± 1.83%)}	_{25.445s (± 1.70%)}	_~	_24.810s	_26.436s	_{p=0.899 n=12}
_{webpack - native}
_Errors	₆₀₂	₆₀₂	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_910,191	_910,191	_~	_~	_~	_{p=1.000 n=12}
_Types	_629,514	_629,514	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{744,885k (± 0.02%)}	_{745,056k (± 0.02%)}	_~	_744,784k	_745,366k	_{p=0.053 n=12}
_{Memory Allocs}	_{6,443,655 (± 0.02%)}	_{6,442,019 (± 0.02%)}	_{-1,636 (- 0.03%)}	_6,439,922	_6,448,318	_{p=0.039 n=12}
_{Config Time}	_0.009s	_0.009s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.317s (± 2.60%)}	_{0.322s (± 2.42%)}	_~	_0.298s	_0.343s	_{p=0.354 n=12}
_{Bind Time}	_{0.087s (±14.50%)}	_{0.085s (±15.67%)}	_~	_0.069s	_0.140s	_{p=0.485 n=12}
_{Check Time}	_{2.664s (± 0.47%)}	_{2.657s (± 0.60%)}	_~	_2.601s	_2.687s	_{p=0.640 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{3.114s (± 0.31%)}	_{3.111s (± 0.41%)}	_~	_3.067s	_3.140s	_{p=0.702 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_640,494	_640,494	_~	_~	_~	_{p=1.000 n=12}
_Types	_387,992	_387,992	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{398,488k (± 0.02%)}	_{398,540k (± 0.02%)}	_~	_398,325k	_398,773k	_{p=0.312 n=12}
_{Memory Allocs}	_{3,992,811 (± 0.07%)}	_{3,993,073 (± 0.05%)}	_~	_3,988,632	_3,997,246	_{p=0.932 n=12}
_{Config Time}	_0.003s	_0.003s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.135s (± 3.53%)}	_{0.133s (± 2.66%)}	_~	_0.125s	_0.143s	_{p=0.599 n=12}
_{Bind Time}	_{0.044s (±13.12%)}	_{0.044s (±14.86%)}	_~	_0.033s	_0.064s	_{p=0.921 n=12}
_{Check Time}	_{0.948s (± 0.57%)}	_{0.948s (± 0.35%)}	_~	_0.936s	_0.957s	_{p=0.743 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.137s (± 0.83%)}	_{1.136s (± 0.67%)}	_~	_1.116s	_1.150s	_{p=0.559 n=12}

System info unknown

Hosts

native

Scenarios

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

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

lsp

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{CompilerLSP - native}
_{Req 1 - updateOpen}	_{10ms (± 8.72%)}	_{11ms (±10.16%)}	_~	_10ms	_15ms	_{p=0.590 n=12}
_{Req 2 - geterr}	_{283ms (± 0.48%)}	_{281ms (± 0.57%)}	_~	_279ms	_286ms	_{p=0.093 n=12}
_{Req 3 - references}	_{49ms (± 2.11%)}	_{48ms (± 1.97%)}	_~	_46ms	_52ms	_{p=0.354 n=12}
_{Req 4 - navto}	_{18ms (± 7.51%)}	_{18ms (± 6.14%)}	_~	_17ms	_23ms	_{p=0.604 n=12}
_{Req 5 - completionInfo count}	_1,525	_1,525	_~	_~	_~	_{p=1.000 n=12}
_{Req 5 - completionInfo}	_{19ms (±10.92%)}	_{21ms (± 8.81%)}	_{🔻+3ms (+13.72%)}	_15ms	_26ms	_{p=0.043 n=12}
_{Compiler-UnionsLSP - native}
_{Req 1 - updateOpen}	_{10ms (± 7.84%)}	_{10ms (±12.61%)}	_~	_9ms	_16ms	_{p=0.243 n=12}
_{Req 2 - geterr}	_{550ms (± 0.34%)}	_{551ms (± 0.35%)}	_~	_546ms	_558ms	_{p=0.305 n=12}
_{Req 3 - references}	_{44ms (± 5.20%)}	_{46ms (± 4.37%)}	_~	_41ms	_49ms	_{p=0.196 n=12}
_{Req 4 - navto}	_{17ms (± 1.95%)}	_{16ms (± 1.75%)}	_~	_16ms	_17ms	_{p=0.214 n=12}
_{Req 5 - completionInfo count}	_1,363	_1,363	_~	_~	_~	_{p=1.000 n=12}
_{Req 5 - completionInfo}	_{16ms (± 6.21%)}	_{16ms (± 9.19%)}	_~	_13ms	_20ms	_{p=0.311 n=12}
_{xstate-main-1-LSP - native}
_{⚠️ Failed}	_failed	_failed

System info unknown

Hosts

native

Scenarios

CompilerLSP - native
Compiler-UnionsLSP - native
xstate-main-1-LSP - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

startup

Comparison Report - baseline..pr

_Metric	_baseline	_pr
_{lsp-startup - native}
_{⚠️ Failed}	_failed	_failed
_{tsgo-startup - native}
_{⚠️ Failed}	_failed	_failed

System info unknown

Hosts

native

Scenarios

lsp-startup - native
tsgo-startup - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

Developer Information:

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Copilot AI balanced review requested due to automatic review settings October 19, 2026 18:45

github-project-automation Bot added this to PR Backlog Oct 19, 2026

github-project-automation Bot moved this to Not started in PR Backlog Oct 19, 2026

typescript-automation Bot assigned Jake Bailey (jakebailey) Oct 19, 2026

typescript-automation Bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Oct 19, 2026

Copilot started reviewing on behalf of Jake Bailey (jakebailey) October 19, 2026 18:46

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Copilot AI reviewed Oct 19, 2026

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Comment thread tsc/internal/checker/utilities.go

Comment on lines +937 to +938

entries []propertyCount

indices map[string]int32

Jake Bailey (jakebailey) force-pushed the perf/intersection-name-counts branch from ee41271 to 4f18092 Compare October 23, 2026 22:24

Jake Bailey (jakebailey) added the Domain: Performance Reports of unusually slow behavior label Oct 27, 2026

Jake Bailey (jakebailey) requested a review from Anders Hejlsberg (ahejlsberg) October 27, 2026 21:15

Anders Hejlsberg (ahejlsberg) approved these changes Oct 27, 2026

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github-project-automation Bot moved this from Not started to Needs merge in PR Backlog Oct 27, 2026

Jake Bailey (jakebailey) added this pull request to the merge queue Oct 27, 2026

Merged via the queue into microsoft:main with commit 615d415 Oct 28, 2026
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Jake Bailey (jakebailey) deleted the perf/intersection-name-counts branch October 28, 2026 00:01

github-project-automation Bot moved this from Needs merge to Done in PR Backlog Oct 28, 2026

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Count intersection property names with a plain map and slice - #64876

Count intersection property names with a plain map and slice#64876
Jake Bailey (jakebailey) merged 1 commit into
microsoft:mainfrom
jakebailey:perf/intersection-name-counts

Jake Bailey (jakebailey) commented Oct 19, 2026 •

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tsc

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tsc

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Jake Bailey (jakebailey) commented Oct 19, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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typescript-automation Bot commented Oct 19, 2026

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Jake Bailey (jakebailey) commented Oct 25, 2026

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typescript-automation Bot commented Oct 25, 2026

tsc

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Jake Bailey (jakebailey) commented Oct 19, 2026 •

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typescript-automation Bot commented Oct 25, 2026 •

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