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

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

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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 }

 func getDeclarationModifierFlagsFromSymbolEx(s *ast.Symbol, isWrite bool) ast.ModifierFlags {
+	if s.CheckFlags&ast.CheckFlagsSynthetic != 0 {


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) 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

Copilot AI reviewed Aug 20, 2026

View reviewed changes

Comment thread tsc/internal/checker/utilities.go

}

func getDeclarationModifierFlagsFromSymbolEx(s *ast.Symbol, isWrite bool) ast.ModifierFlags {

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

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Fix `getDeclarationModifierFlagsFromSymbolEx` for synthetic properties - #63932

Fix `getDeclarationModifierFlagsFromSymbolEx` for synthetic properties#63932
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