Fix `getDeclarationModifierFlagsFromSymbolEx` for synthetic properties by ahejlsberg · Pull Request #63932 · microsoft/TypeScript

Anders Hejlsberg (ahejlsberg) · 2026-08-20T20:22:03Z

This PR corrects and improves checking of set accessor accessibility for properties of unions and intersections of objects. Previously, set accessor accessibility modifiers were effectively ignored in unions and intersections of objects and checking only considered modifiers from get accessors. For example, no errors were reported in the following:

declare class C1 {
    get foo(): number;
    protected set foo(value: number);
}

declare class C2 {
    get foo(): number;
    protected set foo(value: number);
}

declare const c: C1 | C2;
c.foo;        // Ok, read side is public
c.foo = 123;  // Should be an error, write side is protected

With this PR, foo is now correctly considered protected for writing, and an error is reported.

Fixes #63749.

Anders Hejlsberg (ahejlsberg) · 2026-08-20T20:22:23Z

TypeScript Bot (@typescript-bot) test it

typescript-automation · 2026-08-20T20:22:27Z

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

Pull request overview

Fixes synthetic intersection property accessibility so public constituents are not incorrectly treated as protected.

Changes:

Prioritizes aggregate accessibility flags for synthetic symbols.
Adds regression coverage and symbol/type baselines for #63749.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
`tsc/internal/checker/utilities.go`	Changes synthetic modifier resolution order.
`tsc/testdata/tests/cases/compiler/syntheticProtectedProperties.ts`	Adds regression scenarios.
`tsc/testdata/baselines/reference/compiler/syntheticProtectedProperties.types`	Records inferred types.
`tsc/testdata/baselines/reference/compiler/syntheticProtectedProperties.symbols`	Records resolved symbols.

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typescript-automation · 2026-08-20T20:31:35Z

Hey Anders Hejlsberg (@ahejlsberg), it looks like the DT test run failed. Please check the log for more details.

You can check the log here.

typescript-automation · 2026-08-20T20:48:36Z

Anders Hejlsberg (@ahejlsberg)
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	_115,480	_115,480	_~	_~	_~	_{p=1.000 n=12}
_Types	_96,945	_96,945	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{149,139k (± 0.60%)}	_{148,278k (± 0.52%)}	_~	_146,723k	_151,195k	_{p=0.143 n=12}
_{Memory Allocs}	_{2,270,897 (± 0.01%)}	_{2,270,969 (± 0.01%)}	_~	_2,270,639	_2,271,423	_{p=0.434 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.041s (± 3.87%)}	_{0.041s (± 5.01%)}	_~	_0.037s	_0.046s	_{p=0.539 n=12}
_{Bind Time}	_{0.012s (±13.03%)}	_{0.013s (±10.35%)}	_~	_0.010s	_0.016s	_{p=0.113 n=12}
_{Check Time}	_{0.490s (± 1.17%)}	_{0.493s (± 1.32%)}	_~	_0.479s	_0.510s	_{p=0.468 n=12}
_{Emit Time}	_{0.274s (± 2.13%)}	_{0.271s (± 1.75%)}	_~	_0.262s	_0.287s	_{p=0.353 n=12}
_{Total Time}	_{0.823s (± 1.19%)}	_{0.825s (± 1.20%)}	_~	_0.806s	_0.850s	_{p=0.744 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{847,270 (± 0.08%)}	_{847,269 (± 0.07%)}	_~	_845,729	_848,825	_{p=1.000 n=12}
_Types	_{249,860 (± 0.00%)}	_{249,859 (± 0.00%)}	_~	_249,856	_249,861	_{p=0.736 n=12}
_{Memory Used}	_{793,629k (± 0.05%)}	_{793,590k (± 0.06%)}	_~	_792,149k	_795,364k	_{p=0.713 n=12}
_{Memory Allocs}	_{12,955,311 (± 0.04%)}	_{12,952,484 (± 0.02%)}	_~	_12,949,195	_12,959,690	_{p=0.378 n=12}
_{Config Time}	_{0.016s (± 1.13%)}	_{0.016s (± 1.75%)}	_~	_0.016s	_0.017s	_{p=0.590 n=12}
_{Parse Time}	_{0.277s (± 3.27%)}	_{0.271s (± 2.52%)}	_~	_0.253s	_0.288s	_{p=0.097 n=12}
_{Bind Time}	_{0.066s (±17.34%)}	_{0.067s (±15.59%)}	_~	_0.058s	_0.114s	_{p=0.784 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.639s (± 0.77%)}	_{1.642s (± 1.20%)}	_~	_1.611s	_1.718s	_{p=0.854 n=12}
_{Total Time}	_{2.013s (± 0.84%)}	_{2.014s (± 1.60%)}	_~	_1.969s	_2.152s	_{p=0.401 n=12}
_{mui-docs - native}
_Errors	_{11,278 (± 0.04%)}	_{11,278 (± 0.04%)}	_~	_11,255	_11,282	_{p=0.951 n=12}
_Symbols	_4,541,549	_4,541,549	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,639,133	_1,639,133	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{5,548,396k (± 0.02%)}	_{5,548,496k (± 0.02%)}	_~	_5,545,899k	_5,550,817k	_{p=0.932 n=12}
_{Memory Allocs}	_{53,148,040 (± 0.03%)}	_{53,140,343 (± 0.03%)}	_~	_53,109,962	_53,191,655	_{p=0.219 n=12}
_{Config Time}	_{0.016s (± 1.55%)}	_0.016s	_~	_~	_~	_{p=0.478 n=12}
_{Parse Time}	_{0.541s (± 1.84%)}	_{0.553s (± 2.85%)}	_~	_0.494s	_0.583s	_{p=0.091 n=12}
_{Bind Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{14.790s (± 0.89%)}	_{14.823s (± 0.87%)}	_~	_14.599s	_15.287s	_{p=0.932 n=12}
_{Emit Time}	_{0.570s (±13.77%)}	_{0.527s (±10.56%)}	_~	_0.431s	_0.651s	_{p=0.580 n=12}
_{Total Time}	_{16.686s (± 0.89%)}	_{16.671s (± 0.90%)}	_~	_16.312s	_17.043s	_{p=0.977 n=12}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,394,339	_1,394,339	_~	_~	_~	_{p=1.000 n=12}
_Types	_443,465	_443,465	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,652,353k (± 0.38%)}	_{1,646,749k (± 0.31%)}	_~	_1,634,864k	_1,657,879k	_{p=0.160 n=12}
_{Memory Allocs}	_{97,098,524 (± 0.04%)}	_{97,054,099 (± 0.04%)}	_~	_96,945,069	_97,141,403	_{p=0.089 n=12}
_{Config Time}	_{0.004s (±22.35%)}	_{0.004s (±14.99%)}	_~	_0.002s	_0.006s	_{p=0.289 n=12}
_{Parse Time}	_{0.194s (± 2.44%)}	_{0.196s (± 1.79%)}	_~	_0.188s	_0.206s	_{p=0.296 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.780s (± 0.38%)}	_{1.778s (± 0.48%)}	_~	_1.758s	_1.801s	_{p=0.486 n=12}
_{Emit Time}	_{0.293s (± 5.38%)}	_{0.286s (± 5.02%)}	_~	_0.244s	_0.312s	_{p=0.561 n=12}
_{Total Time}	_{24.625s (± 0.67%)}	_{24.570s (± 0.73%)}	_~	_24.097s	_25.261s	_{p=0.579 n=12}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_337,586	_337,586	_~	_~	_~	_{p=1.000 n=12}
_Types	_198,869	_198,869	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{319,552k (± 0.04%)}	_{319,549k (± 0.03%)}	_~	_319,384k	_319,882k	_{p=0.843 n=12}
_{Memory Allocs}	_{4,674,040 (± 0.01%)}	_{4,673,952 (± 0.01%)}	_~	_4,673,257	_4,674,813	_{p=0.799 n=12}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.118s (± 3.80%)}	_{0.120s (± 3.28%)}	_~	_0.113s	_0.131s	_{p=0.433 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.039s (± 0.53%)}	_{1.033s (± 0.48%)}	_~	_1.024s	_1.049s	_{p=0.123 n=12}
_{Emit Time}	_{0.140s (±11.61%)}	_{0.148s (± 9.69%)}	_~	_0.106s	_0.170s	_{p=0.619 n=12}
_{Total Time}	_{1.350s (± 0.70%)}	_{1.354s (± 0.84%)}	_~	_1.319s	_1.383s	_{p=0.681 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_305,317	_305,317	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,984	_181,984	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{277,306k (± 0.03%)}	_{277,251k (± 0.02%)}	_~	_277,098k	_277,415k	_{p=0.160 n=12}
_{Memory Allocs}	_{1,643,337 (± 0.02%)}	_{1,643,116 (± 0.01%)}	_~	_1,642,607	_1,643,797	_{p=0.248 n=12}
_{Config Time}	_{0.000s (±146.91%)}	_0.000s	_~	_~	_~	_{p=0.478 n=12}
_{Parse Time}	_{0.101s (± 3.46%)}	_{0.100s (± 4.36%)}	_~	_0.090s	_0.110s	_{p=0.765 n=12}
_{Bind Time}	_{0.040s (± 9.15%)}	_{0.038s (±13.05%)}	_~	_0.028s	_0.051s	_{p=0.468 n=12}
_{Check Time}	_{0.825s (± 0.46%)}	_{0.827s (± 0.65%)}	_~	_0.810s	_0.839s	_{p=0.368 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.981s (± 0.68%)}	_{0.980s (± 0.71%)}	_~	_0.966s	_1.007s	_{p=0.401 n=12}
_{vscode - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_7,876,305	_7,876,302	_{-3 (- 0.00%)}	_~	_~	_{p=0.000 n=12}
_Types	_2,715,228	_2,715,228	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{5,311,564k (± 0.02%)}	_{5,310,663k (± 0.01%)}	_~	_5,308,854k	_5,312,026k	_{p=0.128 n=12}
_{Memory Allocs}	_{40,958,234 (± 0.01%)}	_{40,954,941 (± 0.01%)}	_~	_40,946,871	_40,962,637	_{p=0.198 n=12}
_{Config Time}	_{0.062s (± 0.43%)}	_{0.062s (± 0.73%)}	_~	_0.061s	_0.064s	_{p=0.752 n=12}
_{Parse Time}	_{1.598s (± 1.35%)}	_{1.586s (± 2.69%)}	_~	_1.444s	_1.662s	_{p=0.966 n=12}
_{Bind Time}	_{0.333s (± 0.51%)}	_{0.387s (±20.25%)}	_~	_0.331s	_0.690s	_{p=0.633 n=12}
_{Check Time}	_{9.973s (± 0.45%)}	_{9.916s (± 1.38%)}	_~	_9.440s	_10.096s	_{p=0.854 n=12}
_{Emit Time}	_{3.064s (± 3.49%)}	_{3.292s (±12.35%)}	_~	_2.969s	_4.714s	_{p=0.713 n=12}
_{Total Time}	_{15.108s (± 0.41%)}	_{15.325s (± 2.08%)}	_~	_15.036s	_16.470s	_{p=0.311 n=12}
_{webpack - native}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,380	_1,380	_~	_~	_~	_{p=1.000 n=12}
_Types	₃₄₀	₃₄₀	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{200,224k (± 0.06%)}	_{200,257k (± 0.05%)}	_~	_200,008k	_200,523k	_{p=0.671 n=12}
_{Memory Allocs}	_{850,409 (± 0.14%)}	_{849,835 (± 0.13%)}	_~	_848,003	_854,138	_{p=0.378 n=12}
_{Config Time}	_{0.009s (± 7.03%)}	_{0.009s (± 7.33%)}	_~	_0.008s	_0.010s	_{p=1.000 n=12}
_{Parse Time}	_{0.235s (± 1.68%)}	_{0.233s (± 2.38%)}	_~	_0.217s	_0.244s	_{p=0.659 n=12}
_{Bind Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.245s (± 1.76%)}	_{0.242s (± 2.35%)}	_~	_0.227s	_0.254s	_{p=0.619 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,019,981	_1,019,981	_~	_~	_~	_{p=1.000 n=12}
_Types	_376,182	_376,182	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{603,450k (± 0.02%)}	_{603,415k (± 0.02%)}	_~	_603,213k	_603,732k	_{p=0.378 n=12}
_{Memory Allocs}	_{4,750,715 (± 0.04%)}	_{4,750,531 (± 0.05%)}	_~	_4,744,298	_4,755,293	_{p=0.932 n=12}
_{Config Time}	_{0.003s (± 6.23%)}	_0.003s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.143s (± 3.53%)}	_{0.147s (± 2.97%)}	_~	_0.136s	_0.159s	_{p=0.339 n=12}
_{Bind Time}	_{0.049s (±19.01%)}	_{0.042s (±17.83%)}	_~	_0.030s	_0.065s	_{p=0.257 n=12}
_{Check Time}	_{1.022s (± 0.91%)}	_{1.030s (± 1.48%)}	_~	_0.986s	_1.064s	_{p=0.326 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.229s (± 1.14%)}	_{1.230s (± 1.26%)}	_~	_1.184s	_1.262s	_{p=0.965 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

typescript-automation · 2026-08-20T20:49:28Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the user tests with tsc comparing main and refs/pull/63932/merge:

There were infrastructure failures potentially unrelated to your change:

2 instances of "Package install failed"
1 instance of "Git clone failed"

Otherwise...

Everything looks good!

typescript-automation · 2026-08-20T21:28:51Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the top 400 repos with tsc comparing main and refs/pull/63932/merge:

Everything looks good!

Anders Hejlsberg (ahejlsberg) · 2026-08-23T21:20:29Z

TypeScript Bot (@typescript-bot) test it

typescript-automation · 2026-08-23T21:20:33Z

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 · 2026-08-23T21:44:04Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the user tests with tsc comparing main and refs/pull/63932/merge:

There were infrastructure failures potentially unrelated to your change:

2 instances of "Package install failed"
1 instance of "Git clone failed"

Otherwise...

Everything looks good!

typescript-automation · 2026-08-23T21:49:32Z

Anders Hejlsberg (@ahejlsberg)
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	_115,480	_115,480	_~	_~	_~	_{p=1.000 n=12}
_Types	_96,945	_96,945	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{148,396k (± 0.38%)}	_{147,754k (± 0.42%)}	_~	_146,295k	_149,743k	_{p=0.128 n=12}
_{Memory Allocs}	_{2,271,215 (± 0.01%)}	_{2,271,251 (± 0.01%)}	_~	_2,270,912	_2,271,612	_{p=0.660 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.042s (± 3.02%)}	_{0.041s (± 2.90%)}	_~	_0.038s	_0.044s	_{p=0.244 n=12}
_{Bind Time}	_{0.012s (±14.80%)}	_{0.013s (±12.00%)}	_~	_0.010s	_0.017s	_{p=0.266 n=12}
_{Check Time}	_{0.487s (± 0.65%)}	_{0.494s (± 1.10%)}	_{+0.007s (+ 1.42%)}	_0.482s	_0.509s	_{p=0.050 n=12}
_{Emit Time}	_{0.272s (± 1.47%)}	_{0.276s (± 2.02%)}	_~	_0.261s	_0.296s	_{p=0.155 n=12}
_{Total Time}	_{0.820s (± 0.70%)}	_{0.831s (± 0.86%)}	_{+0.011s (+ 1.38%)}	_0.813s	_0.846s	_{p=0.027 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{846,920 (± 0.09%)}	_{846,261 (± 0.06%)}	_~	_845,119	_847,691	_{p=0.266 n=12}
_Types	_{249,858 (± 0.00%)}	_{249,859 (± 0.00%)}	_~	_249,856	_249,866	_{p=0.104 n=12}
_{Memory Used}	_{793,398k (± 0.05%)}	_{793,241k (± 0.04%)}	_~	_792,626k	_794,135k	_{p=0.452 n=12}
_{Memory Allocs}	_{12,954,366 (± 0.04%)}	_{12,951,835 (± 0.02%)}	_~	_12,948,975	_12,962,114	_{p=0.590 n=12}
_{Config Time}	_0.016s	_0.016s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.276s (± 1.92%)}	_{0.273s (± 2.20%)}	_~	_0.257s	_0.288s	_{p=0.486 n=12}
_{Bind Time}	_{0.061s (± 7.26%)}	_{0.060s (± 6.47%)}	_~	_0.057s	_0.080s	_{p=0.733 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.624s (± 0.72%)}	_{1.625s (± 0.60%)}	_~	_1.605s	_1.661s	_{p=0.723 n=12}
_{Total Time}	_{1.991s (± 0.83%)}	_{1.990s (± 0.70%)}	_~	_1.958s	_2.042s	_{p=0.659 n=12}
_{mui-docs - native}
_Errors	_{11,278 (± 0.04%)}	_{11,275 (± 0.07%)}	_~	_11,243	_11,282	_{p=0.536 n=12}
_Symbols	_4,293,085	_4,293,085	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,609,812	_1,609,812	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{4,746,434k (± 0.02%)}	_{4,745,204k (± 0.02%)}	_~	_4,742,898k	_4,747,666k	_{p=0.078 n=12}
_{Memory Allocs}	_{47,935,188 (± 0.03%)}	_{47,921,279 (± 0.03%)}	_~	_47,899,776	_47,978,558	_{p=0.078 n=12}
_{Config Time}	_{0.016s (± 1.55%)}	_{0.016s (± 1.14%)}	_~	_0.015s	_0.016s	_{p=1.000 n=12}
_{Parse Time}	_{0.541s (± 2.16%)}	_{0.554s (± 1.30%)}	_~	_0.539s	_0.576s	_{p=0.065 n=12}
_{Bind Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{15.348s (± 0.49%)}	_{15.524s (± 0.39%)}	_{+0.176s (+ 1.15%)}	_15.413s	_15.685s	_{p=0.004 n=12}
_{Emit Time}	_{0.502s (± 7.38%)}	_{0.493s (± 8.80%)}	_~	_0.430s	_0.630s	_{p=0.284 n=12}
_{Total Time}	_{17.216s (± 0.37%)}	_{17.371s (± 0.39%)}	_{+0.155s (+ 0.90%)}	_17.236s	_17.575s	_{p=0.002 n=12}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,394,339	_1,394,339	_~	_~	_~	_{p=1.000 n=12}
_Types	_443,465	_443,465	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,646,545k (± 0.24%)}	_{1,646,768k (± 0.29%)}	_~	_1,633,235k	_1,659,736k	_{p=0.843 n=12}
_{Memory Allocs}	_{97,036,570 (± 0.03%)}	_{97,040,240 (± 0.03%)}	_~	_96,970,706	_97,110,102	_{p=0.977 n=12}
_{Config Time}	_{0.004s (± 8.72%)}	_{0.004s (± 7.93%)}	_~	_0.003s	_0.005s	_{p=0.856 n=12}
_{Parse Time}	_{0.196s (± 2.51%)}	_{0.195s (± 2.96%)}	_~	_0.178s	_0.208s	_{p=0.831 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.787s (± 0.41%)}	_{1.793s (± 0.34%)}	_~	_1.776s	_1.812s	_{p=0.272 n=12}
_{Emit Time}	_{0.279s (± 5.79%)}	_{0.273s (± 4.77%)}	_~	_0.246s	_0.305s	_{p=0.599 n=12}
_{Total Time}	_{24.504s (± 0.63%)}	_{24.568s (± 0.60%)}	_~	_24.156s	_24.968s	_{p=0.378 n=12}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_337,586	_337,586	_~	_~	_~	_{p=1.000 n=12}
_Types	_198,869	_198,869	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{319,586k (± 0.04%)}	_{319,554k (± 0.04%)}	_~	_319,201k	_319,746k	_{p=0.671 n=12}
_{Memory Allocs}	_{4,673,265 (± 0.01%)}	_{4,673,385 (± 0.01%)}	_~	_4,672,180	_4,674,572	_{p=0.843 n=12}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.118s (± 4.64%)}	_{0.116s (± 4.00%)}	_~	_0.103s	_0.131s	_{p=0.541 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.038s (± 0.55%)}	_{1.040s (± 0.44%)}	_~	_1.030s	_1.053s	_{p=0.468 n=12}
_{Emit Time}	_{0.137s (±12.53%)}	_{0.153s (± 6.51%)}	_~	_0.109s	_0.173s	_{p=0.183 n=12}
_{Total Time}	_{1.345s (± 1.18%)}	_{1.358s (± 0.99%)}	_~	_1.316s	_1.400s	_{p=0.203 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_305,317	_305,317	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,984	_181,984	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{277,270k (± 0.02%)}	_{277,252k (± 0.02%)}	_~	_276,995k	_277,396k	_{p=0.671 n=12}
_{Memory Allocs}	_{1,642,301 (± 0.01%)}	_{1,642,396 (± 0.01%)}	_~	_1,642,036	_1,643,032	_{p=0.401 n=12}
_{Config Time}	_{0.000s (±146.91%)}	_0.000s	_~	_~	_~	_{p=0.478 n=12}
_{Parse Time}	_{0.100s (± 3.51%)}	_{0.103s (± 5.17%)}	_~	_0.086s	_0.112s	_{p=0.433 n=12}
_{Bind Time}	_{0.037s (±10.12%)}	_{0.038s (± 9.20%)}	_~	_0.030s	_0.047s	_{p=0.808 n=12}
_{Check Time}	_{0.821s (± 0.59%)}	_{0.830s (± 0.78%)}	_{+0.009s (+ 1.12%)}	_0.811s	_0.849s	_{p=0.025 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.973s (± 0.79%)}	_{0.985s (± 0.60%)}	_{+0.013s (+ 1.30%)}	_0.973s	_0.999s	_{p=0.010 n=12}
_{vscode - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_7,990,947	_7,990,944	_{-3 (- 0.00%)}	_~	_~	_{p=0.000 n=12}
_Types	_2,737,482	_2,737,482	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{5,363,523k (± 0.02%)}	_{5,363,108k (± 0.01%)}	_~	_5,361,820k	_5,365,212k	_{p=0.443 n=12}
_{Memory Allocs}	_{41,285,817 (± 0.02%)}	_{41,280,618 (± 0.01%)}	_~	_41,275,280	_41,290,095	_{p=0.242 n=12}
_{Config Time}	_{0.062s (± 0.53%)}	_{0.063s (± 2.51%)}	_~	_0.062s	_0.071s	_{p=1.000 n=12}
_{Parse Time}	_{1.608s (± 2.51%)}	_{1.624s (± 1.51%)}	_~	_1.554s	_1.670s	_{p=0.799 n=12}
_{Bind Time}	_{0.377s (±15.68%)}	_{0.337s (± 0.39%)}	_~	_0.335s	_0.343s	_{p=0.473 n=12}
_{Check Time}	_{9.810s (± 1.38%)}	_{9.929s (± 0.42%)}	_{+0.119s (+ 1.21%)}	_9.894s	_10.136s	_{p=0.020 n=12}
_{Emit Time}	_{3.279s (±10.65%)}	_{3.030s (± 0.62%)}	_~	_2.978s	_3.059s	_{p=0.173 n=12}
_{Total Time}	_{15.218s (± 1.62%)}	_{15.062s (± 0.34%)}	_~	_14.986s	_15.283s	_{p=0.340 n=12}
_{webpack - native}
_Errors	₇₇₅	₇₇₅	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_846,253	_846,253	_~	_~	_~	_{p=1.000 n=12}
_Types	_385,132	_385,132	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{648,905k (± 0.02%)}	_{648,945k (± 0.03%)}	_~	_648,405k	_649,435k	_{p=0.524 n=12}
_{Memory Allocs}	_{4,352,586 (± 0.04%)}	_{4,351,319 (± 0.02%)}	_~	_4,349,696	_4,354,227	_{p=0.242 n=12}
_{Config Time}	_0.008s	_{0.008s (± 5.88%)}	_~	_0.008s	_0.010s	_{p=0.478 n=12}
_{Parse Time}	_{0.213s (± 2.98%)}	_{0.216s (± 4.03%)}	_~	_0.197s	_0.237s	_{p=0.468 n=12}
_{Bind Time}	_{0.044s (±12.94%)}	_{0.047s (± 8.91%)}	_{🔻+0.002s (+ 5.47%)}	_0.041s	_0.062s	_{p=0.017 n=12}
_{Check Time}	_{1.225s (± 1.01%)}	_{1.265s (± 2.88%)}	_~	_1.199s	_1.359s	_{p=0.173 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.518s (± 0.87%)}	_{1.569s (± 2.73%)}	_~	_1.486s	_1.672s	_{p=0.110 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,019,981	_1,019,981	_~	_~	_~	_{p=1.000 n=12}
_Types	_376,182	_376,182	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{603,408k (± 0.01%)}	_{603,434k (± 0.01%)}	_~	_603,237k	_603,691k	_{p=0.671 n=12}
_{Memory Allocs}	_{4,752,253 (± 0.04%)}	_{4,748,723 (± 0.03%)}	_{-3,530 (- 0.07%)}	_4,744,666	_4,751,923	_{p=0.010 n=12}
_{Config Time}	_0.003s	_0.003s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.145s (± 2.90%)}	_{0.147s (± 3.84%)}	_~	_0.138s	_0.166s	_{p=0.831 n=12}
_{Bind Time}	_{0.042s (±14.25%)}	_{0.045s (±17.86%)}	_~	_0.033s	_0.067s	_{p=0.721 n=12}
_{Check Time}	_{1.012s (± 0.91%)}	_{1.028s (± 1.28%)}	_~	_0.999s	_1.074s	_{p=0.061 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.213s (± 1.05%)}	_{1.235s (± 1.34%)}	_{+0.021s (+ 1.77%)}	_1.190s	_1.276s	_{p=0.040 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

typescript-automation · 2026-08-23T21:56:20Z

Hey Anders Hejlsberg (@ahejlsberg), the results of running the DT tests are ready.

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typescript-automation · 2026-08-23T22:19:03Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the top 400 repos with tsc comparing main and refs/pull/63932/merge:

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Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

Suppressed comments (1)

tsc/internal/checker/utilities.go:718

This branch now bypasses the ValueDeclaration path for every synthetic symbol, so it drops non-accessibility modifiers that were previously preserved. createUnionOrIntersectionProperty can assign a shared ValueDeclaration to a synthetic result (checker.go:21766-21769), and checkPropertyAccessibilityAtLocation relies on the returned Abstract flag to reject abstract super accesses and constructor reads (checker.go:11887-11917). A synthetic property formed from multiple instantiations of the same abstract declaration will therefore be treated as non-abstract. Please merge the synthetic read/write accessibility with the non-accessibility flags from the selected value declaration instead of returning only accessibility and Static.

	if s.CheckFlags&ast.CheckFlagsSynthetic != 0 {

Jake Bailey (jakebailey) · 2026-08-24T17:41:40Z

There's a suppressed comment but seems plausible?

Anders Hejlsberg (ahejlsberg) · 2026-08-24T17:51:20Z

There's a suppressed comment but seems plausible?

I think its very dubious to speculate about abstract properties from unions or intersections that, by definition, don't actually refer to a single class. It's really an implementation attribute, specific to a class, that matters when you inherit from that class. For the same reason, we don't have abstract interfaces.

Anders Hejlsberg (ahejlsberg) added 2 commits August 20, 2026 13:19

Fix getDeclarationModifierFlagsFromSymbolEx for synthetic properties

3bb8f58

Add regression test

3d75121

Copilot AI balanced review requested due to automatic review settings August 20, 2026 20:22

github-project-automation Bot added this to PR Backlog Aug 20, 2026

typescript-automation Bot assigned Anders Hejlsberg (ahejlsberg) Aug 20, 2026

github-project-automation Bot moved this to Not started in PR Backlog Aug 20, 2026

typescript-automation Bot added Author: Team For Milestone Bug PRs that fix a bug with a specific milestone labels Aug 20, 2026

Copilot started reviewing on behalf of Anders Hejlsberg (ahejlsberg) August 20, 2026 20:22 View session

Anders Hejlsberg (ahejlsberg) requested review from Ryan Cavanaugh (RyanCavanaugh) and Jake Bailey (jakebailey) August 20, 2026 20:24

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Comment thread tsc/internal/checker/utilities.go

Anders Hejlsberg (ahejlsberg) added 6 commits August 21, 2026 17:24

Properly track set accessor modifiers in unions/intersections

ed035d4

Handle differing read/write accessibility in union properties

d9d7497

Add tests

07ef369

Fix union accessibility and error reporting on private properties

56d619b

Add more tests

9c9c51f

Accept new baselines

b194b9d

Generate enums

0156173

Anders Hejlsberg (ahejlsberg) added this to the TypeScript 7.1 milestone Aug 23, 2026

Copilot stopped work on behalf of Handwerk-direkt-24 due to an error August 24, 2026 00:03
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Copilot stopped work on behalf of Handwerk-direkt-24 due to an error August 24, 2026 00:13
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Anders Hejlsberg (ahejlsberg) added 2 commits August 23, 2026 18:43

Merge branch 'main' into fix-63749

2b37350

Accept new baselines

78fc649

Jake Bailey (jakebailey) requested a balanced review from Copilot August 24, 2026 17:35

Copilot started reviewing on behalf of Jake Bailey (jakebailey) August 24, 2026 17:36 View session

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Jake Bailey (jakebailey) approved these changes Aug 24, 2026

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github-project-automation Bot moved this from Not started to Needs merge in PR Backlog Aug 24, 2026

Anders Hejlsberg (ahejlsberg) added this pull request to the merge queue Aug 24, 2026

Merged via the queue into main with commit 8239985 Aug 24, 2026
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Anders Hejlsberg (ahejlsberg) deleted the fix-63749 branch August 24, 2026 22:25

github-project-automation Bot moved this from Needs merge to Done in PR Backlog Aug 24, 2026

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Anders Hejlsberg (ahejlsberg) commented Aug 20, 2026 •

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