Key deferred indexed access types by their persistent access flags by jakebailey · Pull Request #65450 · microsoft/TypeScript

Jake Bailey (jakebailey) · 2026-11-12T00:51:48Z

This is just a porting bug

Strada (src/compiler/checker.ts, in getIndexedAccessTypeOrUndefined):

// Defer the operation by creating an indexed access type.
const persistentAccessFlags = accessFlags & AccessFlags.Persistent;
const id = objectType.id + "," + indexType.id + "," + persistentAccessFlags + getAliasId(aliasSymbol, aliasTypeArguments);
let type = indexedAccessTypes.get(id);
if (!type) {
    indexedAccessTypes.set(id, type = createIndexedAccessType(objectType, indexType, persistentAccessFlags, aliasSymbol, aliasTypeArguments));
}
return type;

Go on main (tsc/internal/checker/checker.go:27786):

// Defer the operation by creating an indexed access type.
persistentAccessFlags := accessFlags & AccessFlagsPersistent
key := getIndexedAccessKey(objectType, indexType, accessFlags, alias)   // ← should be persistentAccessFlags
t := c.indexedAccessTypes[key]
if t == nil {
    t = c.newIndexedAccessType(objectType, indexType, persistentAccessFlags)
    t.alias = alias
    c.indexedAccessTypes[key] = t
}
return t

The fix changes that one argument back to persistentAccessFlags.

Reading obj[key] with a key of a union of type parameters gives a type that should be identical to T[K1 | K2] written in a type annotation. It is reported as not assignable to it, which TypeScript 6.0 accepts.

An indexed access type keeps only the persistent access flags, but the cache of deferred indexed access types was keyed by all of them, so an access made in an expression created a second type identical to the one written in a type annotation. Relating the two then could not use their identity, and simplified the source for reading and the target for writing, which are not related when the index is a union. TypeScript 6.0 keys the cache by the persistent access flags.

Jake Bailey (jakebailey) · 2026-11-12T00:53:56Z

TypeScript Bot (@typescript-bot) test it

typescript-automation · 2026-11-12T00:54:02Z

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

Copilot

🟢 Approval recommended

No active review issues are reported for the indexed-access cache-key fix and its regression coverage.

No open issues 🎉

What changed in this PR

Fixes a porting bug in the native TypeScript checker by using persistent access flags consistently when caching deferred indexed access types.

Changes:

Aligns the cache key with the flags stored on the indexed access type.
Adds regression cases for generic union-key accesses, with expected type and symbol baselines.

File	Description
`tsc/testdata/tests/cases/compiler/indexedAccessUnionKeyIdentity.ts`	Adds regression coverage for indexed access type identity.
`tsc/testdata/baselines/reference/compiler/indexedAccessUnionKeyIdentity.types`	Records expected types for the regression cases.
`tsc/testdata/baselines/reference/compiler/indexedAccessUnionKeyIdentity.symbols`	Records expected symbol bindings for the regression cases.
`tsc/internal/checker/checker.go`	Uses persistent access flags in the deferred indexed access cache key.

_{Review effort: Balanced}

typescript-automation · 2026-11-12T01:23:20Z

Jake Bailey (@jakebailey) Here are the results of running the user tests with tsc comparing baseline and pr:

Everything looks good!

typescript-automation · 2026-11-12T01:23:21Z

Hey Jake Bailey (@jakebailey), the results of running the DT tests are ready.

Everything looks the same!

You can check the log here.

typescript-automation · 2026-11-12T01:34:45Z

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=40}
_Symbols	_88,466	_88,466	_~	_~	_~	_{p=1.000 n=40}
_Types	_79,607	_79,606	_{-1 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{106,397k (± 0.02%)}	_{106,403k (± 0.02%)}	_~	_106,285k	_106,588k	_{p=0.685 n=40}
_{Memory Allocs}	_{1,261,904 (± 0.00%)}	_{1,261,906 (± 0.01%)}	_~	_1,261,452	_1,262,314	_{p=0.847 n=40}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Parse Time}	_{0.022s (± 1.80%)}	_{0.022s (± 1.90%)}	_~	_0.019s	_0.024s	_{p=0.325 n=40}
_{Bind Time}	_{0.008s (± 3.75%)}	_{0.008s (± 3.51%)}	_~	_0.006s	_0.010s	_{p=0.306 n=40}
_{Check Time}	_{0.201s (± 0.58%)}	_{0.202s (± 1.26%)}	_~	_0.193s	_0.248s	_{p=0.988 n=40}
_{Emit Time}	_{0.130s (± 1.79%)}	_{0.129s (± 0.58%)}	_~	_0.125s	_0.138s	_{p=0.455 n=40}
_{Total Time}	_{0.364s (± 0.72%)}	_{0.363s (± 0.79%)}	_~	_0.356s	_0.415s	_{p=0.557 n=40}
_{angular-1 - native}
_Errors	₆₃	₆₃	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_756,637	_756,637	_~	_~	_~	_{p=1.000 n=40}
_Types	_549,451	_549,423	_{-28 (- 0.01%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{643,887k (± 0.01%)}	_{643,885k (± 0.01%)}	_~	_643,298k	_644,620k	_{p=0.637 n=40}
_{Memory Allocs}	_{9,554,330 (± 0.02%)}	_{9,556,650 (± 0.09%)}	_~	_9,548,789	_9,717,958	_{p=0.695 n=40}
_{Config Time}	_{0.007s (± 2.02%)}	_{0.007s (± 2.16%)}	_~	_0.006s	_0.007s	_{p=0.158 n=40}
_{Parse Time}	_{0.115s (± 2.45%)}	_{0.118s (± 3.24%)}	_~	_0.105s	_0.163s	_{p=0.183 n=40}
_{Bind Time}	_{0.041s (± 6.62%)}	_{0.041s (± 6.72%)}	_~	_0.034s	_0.067s	_{p=0.872 n=40}
_{Check Time}	_{0.618s (± 0.82%)}	_{0.617s (± 0.99%)}	_~	_0.588s	_0.685s	_{p=0.637 n=40}
_{Emit Time}	_{0.390s (± 0.51%)}	_{0.389s (± 0.39%)}	_~	_0.383s	_0.402s	_{p=0.694 n=40}
_{Total Time}	_{1.184s (± 0.41%)}	_{1.186s (± 0.45%)}	_~	_1.157s	_1.238s	_{p=0.755 n=40}
_{arktype - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_686,116	_686,116	_~	_~	_~	_{p=1.000 n=40}
_Types	_939,797	_939,781	_{-16 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{475,955k (± 0.01%)}	_{475,948k (± 0.01%)}	_~	_475,569k	_476,164k	_{p=0.646 n=40}
_{Memory Allocs}	_{12,063,922 (± 0.01%)}	_{12,065,842 (± 0.02%)}	_~	_12,058,844	_12,081,942	_{p=0.314 n=40}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=40}
_{Parse Time}	_{0.039s (± 2.39%)}	_{0.040s (± 2.61%)}	_~	_0.033s	_0.048s	_{p=0.164 n=40}
_{Bind Time}	_{0.013s (± 5.54%)}	_{0.013s (± 5.62%)}	_~	_0.010s	_0.020s	_{p=1.000 n=40}
_{Check Time}	_{0.833s (± 0.38%)}	_{0.831s (± 0.42%)}	_~	_0.804s	_0.851s	_{p=0.323 n=40}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Total Time}	_{0.912s (± 0.29%)}	_{0.912s (± 0.34%)}	_~	_0.886s	_0.933s	_{p=0.795 n=40}
_{class-transformer - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_45,376	_45,376	_~	_~	_~	_{p=1.000 n=40}
_Types	_7,573	_7,573	_~	_~	_~	_{p=1.000 n=40}
_{Memory Used}	_{27,746k (± 0.02%)}	_{27,744k (± 0.02%)}	_~	_27,703k	_27,775k	_{p=0.443 n=40}
_{Memory Allocs}	_{248,577 (± 0.04%)}	_{248,479 (± 0.04%)}	_~	_247,953	_249,454	_{p=0.192 n=40}
_{Config Time}	_{0.001s (±17.67%)}	_{0.001s (±19.97%)}	_~	_0.000s	_0.001s	_{p=0.543 n=40}
_{Parse Time}	_{0.011s (± 2.87%)}	_{0.011s (± 2.59%)}	_~	_0.008s	_0.012s	_{p=0.855 n=40}
_{Bind Time}	_{0.003s (± 8.57%)}	_{0.003s (± 7.17%)}	_{🟩-0.000s (-13.40%)}	_0.002s	_0.005s	_{p=0.021 n=40}
_{Check Time}	_{0.008s (± 4.30%)}	_{0.008s (± 3.36%)}	_~	_0.006s	_0.009s	_{p=0.399 n=40}
_{Emit Time}	_{0.007s (± 4.20%)}	_{0.007s (± 3.84%)}	_~	_0.006s	_0.009s	_{p=0.418 n=40}
_{Total Time}	_{0.031s (± 1.82%)}	_{0.030s (± 1.32%)}	_~	_0.026s	_0.032s	_{p=0.095 n=40}
_{effect - native}
_Errors	₁₂	₁₂	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_1,235,134	_1,235,134	_~	_~	_~	_{p=1.000 n=40}
_Types	_893,436	_893,420	_{-16 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{941,319k (± 0.02%)}	_{941,327k (± 0.02%)}	_~	_940,267k	_942,470k	_{p=0.826 n=40}
_{Memory Allocs}	_{12,629,628 (± 0.04%)}	_{12,629,770 (± 0.04%)}	_~	_12,611,673	_12,684,964	_{p=0.868 n=40}
_{Config Time}	_{0.002s (± 7.23%)}	_{0.002s (± 5.87%)}	_~	_0.002s	_0.004s	_{p=0.184 n=40}
_{Parse Time}	_{0.154s (± 1.32%)}	_{0.153s (± 1.18%)}	_~	_0.140s	_0.164s	_{p=0.350 n=40}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Check Time}	_{0.907s (± 0.67%)}	_{0.910s (± 1.12%)}	_~	_0.851s	_1.045s	_{p=1.000 n=40}
_{Emit Time}	_{0.504s (± 1.46%)}	_{0.497s (± 1.20%)}	_~	_0.435s	_0.541s	_{p=0.183 n=40}
_{Total Time}	_{1.664s (± 0.67%)}	_{1.658s (± 0.81%)}	_~	_1.553s	_1.833s	_{p=0.248 n=40}
_{mui-docs - native}
_Errors	_11,405	_11,405	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_3,782,394	_3,782,394	_~	_~	_~	_{p=1.000 n=40}
_Types	_1,355,778	_1,355,774	_{-4 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{1,679,300k (± 0.05%)}	_{1,678,800k (± 0.05%)}	_~	_1,671,550k	_1,684,194k	_{p=0.599 n=40}
_{Memory Allocs}	_{25,608,428 (± 0.04%)}	_{25,605,989 (± 0.06%)}	_~	_25,531,551	_25,767,365	_{p=0.510 n=40}
_{Config Time}	_{0.006s (± 0.80%)}	_{0.006s (± 0.07%)}	_~	_0.006s	_0.006s	_{p=1.000 n=40}
_{Parse Time}	_{0.268s (± 2.12%)}	_{0.268s (± 1.82%)}	_~	_0.237s	_0.314s	_{p=0.917 n=40}
_{Bind Time}	_{0.001s (± 1.13%)}	_{0.001s (±13.09%)}	_~	_0.001s	_0.004s	_{p=1.000 n=40}
_{Check Time}	_{2.788s (± 0.43%)}	_{2.785s (± 0.61%)}	_~	_2.720s	_3.033s	_{p=0.563 n=40}
_{Emit Time}	_{0.237s (± 0.84%)}	_{0.239s (± 0.96%)}	_~	_0.223s	_0.266s	_{p=0.451 n=40}
_{Total Time}	_{3.769s (± 0.37%)}	_{3.767s (± 0.64%)}	_~	_3.690s	_4.161s	_{p=0.295 n=40}
_{sentry - native}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_4,793,266	_4,793,266	_~	_~	_~	_{p=1.000 n=40}
_Types	_2,607,066	_2,607,044	_{-22 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{2,797,956k (± 0.03%)}	_{2,798,407k (± 0.03%)}	_~	_2,795,204k	_2,807,027k	_{p=0.283 n=40}
_{Memory Allocs}	_{74,652,663 (± 0.05%)}	_{74,674,545 (± 0.06%)}	_~	_74,321,442	_75,172,325	_{p=0.501 n=40}
_{Config Time}	_{0.018s (± 0.82%)}	_{0.018s (± 1.16%)}	_~	_0.017s	_0.020s	_{p=0.977 n=40}
_{Parse Time}	_{0.454s (± 3.24%)}	_{0.455s (± 2.80%)}	_~	_0.401s	_0.625s	_{p=0.867 n=40}
_{Bind Time}	_{0.135s (± 4.81%)}	_{0.140s (± 6.32%)}	_~	_0.122s	_0.219s	_{p=0.856 n=40}
_{Check Time}	_{6.425s (± 0.44%)}	_{6.417s (± 0.47%)}	_~	_6.226s	_6.684s	_{p=0.545 n=40}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Total Time}	_{7.081s (± 0.41%)}	_{7.079s (± 0.48%)}	_~	_6.899s	_7.505s	_{p=0.572 n=40}
_{social-app - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_1,883,060	_1,883,060	_~	_~	_~	_{p=1.000 n=40}
_Types	_1,158,093	_1,158,079	_{-14 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{952,511k (± 0.01%)}	_{952,326k (± 0.01%)}	_{-130k (- 0.01%)}	_951,271k	_952,999k	_{p=0.022 n=40}
_{Memory Allocs}	_{13,439,811 (± 0.09%)}	_{13,447,447 (± 0.09%)}	_~	_13,387,097	_13,536,169	_{p=0.444 n=40}
_{Config Time}	_{0.005s (± 2.57%)}	_{0.005s (± 2.51%)}	_~	_0.005s	_0.006s	_{p=0.375 n=40}
_{Parse Time}	_{0.150s (± 1.86%)}	_{0.150s (± 1.71%)}	_~	_0.138s	_0.172s	_{p=0.507 n=40}
_{Bind Time}	_{0.039s (± 6.01%)}	_{0.041s (± 5.18%)}	_~	_0.033s	_0.059s	_{p=0.054 n=40}
_{Check Time}	_{1.353s (± 0.51%)}	_{1.349s (± 0.55%)}	_~	_1.309s	_1.400s	_{p=0.247 n=40}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Total Time}	_{1.564s (± 0.38%)}	_{1.565s (± 0.43%)}	_~	_1.528s	_1.620s	_{p=0.874 n=40}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_1,184,972	_1,184,972	_~	_~	_~	_{p=1.000 n=40}
_Types	_438,823	_438,812	_{-11 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{1,154,800k (± 0.12%)}	_{1,157,759k (± 0.20%)}	_~	_1,146,667k	_1,178,595k	_{p=0.060 n=40}
_{Memory Allocs}	_{47,847,317 (± 0.07%)}	_{47,866,110 (± 0.06%)}	_~	_47,686,278	_48,062,943	_{p=0.460 n=40}
_{Config Time}	_{0.002s (±12.33%)}	_{0.002s (± 9.72%)}	_~	_0.000s	_0.003s	_{p=0.980 n=40}
_{Parse Time}	_{0.135s (± 1.22%)}	_{0.134s (± 1.19%)}	_~	_0.122s	_0.144s	_{p=0.525 n=40}
_{Bind Time}	_0.000s	_{0.000s (±196.00%)}	_~	_0.000s	_0.001s	_{p=0.330 n=40}
_{Check Time}	_{0.784s (± 0.26%)}	_{0.784s (± 0.54%)}	_~	_0.767s	_0.832s	_{p=0.872 n=40}
_{Emit Time}	_{0.135s (± 1.10%)}	_{0.137s (± 1.24%)}	_~	_0.129s	_0.154s	_{p=0.229 n=40}
_{Total Time}	_{9.116s (± 0.23%)}	_{9.154s (± 0.47%)}	_~	_9.009s	_9.571s	_{p=0.428 n=40}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_263,481	_263,481	_~	_~	_~	_{p=1.000 n=40}
_Types	_196,103	_196,095	_{-8 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{221,546k (± 0.02%)}	_{221,495k (± 0.01%)}	_{-50k (- 0.02%)}	_221,220k	_221,652k	_{p=0.048 n=40}
_{Memory Allocs}	_{2,412,351 (± 0.01%)}	_{2,412,400 (± 0.01%)}	_~	_2,409,660	_2,414,520	_{p=0.627 n=40}
_{Config Time}	_{0.000s (±196.00%)}	_{0.000s (±110.22%)}	_~	_0.000s	_0.001s	_{p=0.314 n=40}
_{Parse Time}	_{0.049s (± 2.12%)}	_{0.051s (± 7.24%)}	_~	_0.041s	_0.100s	_{p=0.862 n=40}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Check Time}	_{0.371s (± 0.72%)}	_{0.370s (± 0.46%)}	_~	_0.357s	_0.387s	_{p=0.763 n=40}
_{Emit Time}	_{0.050s (± 3.81%)}	_{0.049s (± 3.78%)}	_~	_0.040s	_0.062s	_{p=0.469 n=40}
_{Total Time}	_{0.496s (± 0.73%)}	_{0.498s (± 0.94%)}	_~	_0.476s	_0.553s	_{p=0.624 n=40}
_{t3code-server - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_4,349,937	_4,349,937	_~	_~	_~	_{p=1.000 n=40}
_Types	_3,042,465	_3,042,462	_{-3 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{2,394,841k (± 0.02%)}	_{2,395,634k (± 0.03%)}	_~	_2,392,799k	_2,402,525k	_{p=0.211 n=40}
_{Memory Allocs}	_{37,065,577 (± 0.03%)}	_{37,067,783 (± 0.02%)}	_~	_37,001,505	_37,122,583	_{p=0.889 n=40}
_{Config Time}	_{0.002s (± 5.89%)}	_{0.002s (± 6.38%)}	_~	_0.002s	_0.003s	_{p=0.663 n=40}
_{Parse Time}	_{0.248s (± 1.62%)}	_{0.244s (± 1.45%)}	_~	_0.216s	_0.266s	_{p=0.127 n=40}
_{Bind Time}	_{0.088s (± 7.26%)}	_{0.090s (± 7.26%)}	_~	_0.072s	_0.142s	_{p=0.610 n=40}
_{Check Time}	_{5.864s (± 0.51%)}	_{5.883s (± 0.94%)}	_~	_5.559s	_6.776s	_{p=0.874 n=40}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Total Time}	_{6.216s (± 0.50%)}	_{6.233s (± 0.89%)}	_~	_5.898s	_7.114s	_{p=0.868 n=40}
_{tanstack-router - native}
_Errors	₁	₁	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_570,149	_570,149	_~	_~	_~	_{p=1.000 n=40}
_Types	_396,551	_396,548	_{-3 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{315,267k (± 0.01%)}	_{315,234k (± 0.01%)}	_~	_315,015k	_315,427k	_{p=0.295 n=40}
_{Memory Allocs}	_{4,332,328 (± 0.09%)}	_{4,335,314 (± 0.12%)}	_~	_4,320,785	_4,400,055	_{p=0.253 n=40}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=40}
_{Parse Time}	_{0.040s (± 2.45%)}	_{0.039s (± 2.86%)}	_~	_0.033s	_0.048s	_{p=0.143 n=40}
_{Bind Time}	_{0.013s (± 7.17%)}	_{0.013s (± 7.79%)}	_~	_0.010s	_0.023s	_{p=0.538 n=40}
_{Check Time}	_{0.460s (± 0.74%)}	_{0.459s (± 0.91%)}	_~	_0.444s	_0.521s	_{p=0.480 n=40}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Total Time}	_{0.532s (± 0.72%)}	_{0.528s (± 0.80%)}	_~	_0.511s	_0.587s	_{p=0.149 n=40}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_231,607	_231,607	_~	_~	_~	_{p=1.000 n=40}
_Types	_181,163	_181,149	_{-14 (- 0.01%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{190,838k (± 0.01%)}	_{190,842k (± 0.01%)}	_~	_190,682k	_190,981k	_{p=0.868 n=40}
_{Memory Allocs}	_{1,310,135 (± 0.01%)}	_{1,310,212 (± 0.01%)}	_~	_1,309,255	_1,311,414	_{p=0.554 n=40}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Parse Time}	_{0.046s (± 6.23%)}	_{0.045s (± 2.20%)}	_~	_0.040s	_0.052s	_{p=0.600 n=40}
_{Bind Time}	_{0.021s (± 3.91%)}	_{0.020s (± 3.09%)}	_~	_0.017s	_0.025s	_{p=0.118 n=40}
_{Check Time}	_{0.306s (± 1.22%)}	_{0.303s (± 0.58%)}	_~	_0.289s	_0.314s	_{p=0.264 n=40}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Total Time}	_{0.380s (± 1.77%)}	_{0.375s (± 0.48%)}	_~	_0.361s	_0.390s	_{p=0.151 n=40}
_{vscode - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_8,172,850	_8,172,850	_~	_~	_~	_{p=1.000 n=40}
_Types	_4,755,502	_4,755,363	_{-139 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{5,461,043k (± 0.01%)}	_{5,460,605k (± 0.01%)}	_~	_5,457,103k	_5,465,200k	_{p=0.242 n=40}
_{Memory Allocs}	_{61,073,362 (± 0.02%)}	_{61,069,826 (± 0.01%)}	_~	_61,045,586	_61,160,885	_{p=0.618 n=40}
_{Config Time}	_{0.023s (± 0.64%)}	_{0.023s (± 0.58%)}	_~	_0.022s	_0.024s	_{p=0.146 n=40}
_{Parse Time}	_{0.901s (± 1.42%)}	_{0.898s (± 1.18%)}	_~	_0.802s	_0.984s	_{p=0.837 n=40}
_{Bind Time}	_{0.323s (± 4.62%)}	_{0.324s (± 6.02%)}	_~	_0.285s	_0.527s	_{p=0.634 n=40}
_{Check Time}	_{7.346s (± 0.51%)}	_{7.370s (± 0.48%)}	_~	_7.133s	_7.675s	_{p=0.590 n=40}
_{Emit Time}	_{2.351s (± 5.33%)}	_{2.258s (± 4.94%)}	_~	_1.919s	_3.034s	_{p=0.452 n=40}
_{Total Time}	_{11.011s (± 0.87%)}	_{10.931s (± 0.85%)}	_~	_10.611s	_11.586s	_{p=0.301 n=40}
_{webpack - native}
_Errors	₆₁₈	₆₁₈	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_910,313	_910,313	_~	_~	_~	_{p=1.000 n=40}
_Types	_636,663	_636,598	_{-65 (- 0.01%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{666,707k (± 0.01%)}	_{666,715k (± 0.01%)}	_~	_666,133k	_667,254k	_{p=0.725 n=40}
_{Memory Allocs}	_{6,228,354 (± 0.08%)}	_{6,227,147 (± 0.10%)}	_~	_6,210,324	_6,309,748	_{p=0.666 n=40}
_{Config Time}	_0.003s	_0.003s	_~	_~	_~	_{p=1.000 n=40}
_{Parse Time}	_{0.124s (± 1.48%)}	_{0.124s (± 2.11%)}	_~	_0.111s	_0.149s	_{p=0.763 n=40}
_{Bind Time}	_{0.039s (± 4.89%)}	_{0.042s (± 6.62%)}	_~	_0.033s	_0.061s	_{p=0.068 n=40}
_{Check Time}	_{1.097s (± 0.53%)}	_{1.093s (± 0.53%)}	_~	_1.062s	_1.144s	_{p=0.287 n=40}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Total Time}	_{1.287s (± 0.38%)}	_{1.286s (± 0.41%)}	_~	_1.252s	_1.324s	_{p=0.633 n=40}
_{xstate-main - native}
_Errors	₁	₁	_~	_~	_~	_{p=1.000 n=40}
_Symbols	_3,931,440	_3,931,440	_~	_~	_~	_{p=1.000 n=40}
_Types	_3,960,073	_3,960,045	_{-28 (- 0.00%)}	_~	_~	_{p=0.000 n=40}
_{Memory Used}	_{2,137,563k (± 0.01%)}	_{2,137,601k (± 0.01%)}	_~	_2,136,921k	_2,138,748k	_{p=0.627 n=40}
_{Memory Allocs}	_{42,225,911 (± 0.01%)}	_{42,221,814 (± 0.01%)}	_~	_42,195,653	_42,237,732	_{p=0.097 n=40}
_{Config Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=40}
_{Parse Time}	_{0.108s (± 1.61%)}	_{0.105s (± 1.68%)}	_{-0.003s (- 2.41%)}	_0.093s	_0.115s	_{p=0.036 n=40}
_{Bind Time}	_{0.039s (± 5.72%)}	_{0.040s (± 7.34%)}	_~	_0.032s	_0.060s	_{p=0.948 n=40}
_{Check Time}	_{4.154s (± 0.52%)}	_{4.187s (± 0.62%)}	_{+0.031s (+ 0.74%)}	_4.031s	_4.479s	_{p=0.030 n=40}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=40}
_{Total Time}	_{4.311s (± 0.48%)}	_{4.341s (± 0.59%)}	_{+0.028s (+ 0.65%)}	_4.192s	_4.641s	_{p=0.045 n=40}

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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typescript-automation · 2026-11-12T02:19:20Z

Jake Bailey (@jakebailey) Here are the results of running the top 400 repos with tsc comparing baseline and pr:

Everything looks good!

Jake Bailey (jakebailey) added 2 commits November 11, 2026 16:39

Add a test for indexed access types with a union index

3f1e86a

Reading obj[key] with a key of a union of type parameters gives a type that should be identical to T[K1 | K2] written in a type annotation. It is reported as not assignable to it, which TypeScript 6.0 accepts.

Jake Bailey (jakebailey) requested review from Daniel Rosenwasser (DanielRosenwasser), Andrew Branch (andrewbranch) and Gabriela Araujo Britto (gabritto) November 12, 2026 00:51

typescript-automation Bot assigned Jake Bailey (jakebailey) Nov 12, 2026

typescript-automation Bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Nov 12, 2026

Jake Bailey (jakebailey) marked this pull request as ready for review November 12, 2026 00:51

Copilot AI balanced review requested due to automatic review settings November 12, 2026 00:51

Jake Bailey (jakebailey) mentioned this pull request Nov 12, 2026

[experiment] fully order independent type checking #65064

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Key deferred indexed access types by their persistent access flags - #65450

Key deferred indexed access types by their persistent access flags#65450
Jake Bailey (jakebailey) wants to merge 2 commits into
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jakebailey:indexed-access-key-flags

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