Properly propagate `ObjectFlags.NonInferrableType` onto non-aliased anonymous object types instantiations by Andarist · Pull Request #62346 · microsoft/TypeScript

Mateusz Burzyński (Andarist) · 2025-08-27T21:57:05Z

…nonymous object types instantiations

Copilot

Pull Request Overview

This PR fixes the proper propagation of ObjectFlags.NonInferrableType onto non-aliased anonymous object type instantiations, addressing issue #62345. The fix ensures that when instantiating generic types, certain object flags (including NonInferrableType) are properly carried forward from the type arguments to the resulting instantiated type.

Extracts propagating flags from type arguments before computing type variable containment
Applies all propagating flags (including NonInferrableType) to the result object type
Adds comprehensive test coverage for various scenarios where non-inferrable type propagation should occur

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/cases/compiler/nonInferrableTypePropagation4.ts	Adds test cases covering object types, type aliases, arrays, and nested structures
tests/baselines/reference/nonInferrableTypePropagation4.types	Expected type inference baseline showing `unknown` types in results
tests/baselines/reference/nonInferrableTypePropagation4.symbols	Expected symbol resolution baseline for the test
tests/baselines/reference/nonInferrableTypePropagation4.errors.txt	Expected compilation errors showing type assignment failures
src/compiler/checker.ts	Core fix in type instantiation logic to propagate object flags properly

Mateusz Burzyński (Andarist) · 2025-08-27T21:58:29Z

- else {
- (result as ObjectFlagsType).objectFlags |= !resultCouldContainTypeVariables ? ObjectFlags.CouldContainTypeVariablesComputed : 0;
+ if (result.flags & TypeFlags.ObjectFlagsType) {
+ let propagatingFlags = getPropagatingFlagsOfTypes(typeArguments);


Propagating from typeArguments is the core of the fix, the rest is just adjusted indentation.
You can also find some prior related discussion here: #49887 (comment)

Ryan Cavanaugh (RyanCavanaugh) · 2025-08-27T21:59:49Z

TypeScript Bot (@typescript-bot) test it

TypeScript Bot (typescript-bot) · 2025-08-27T21:59:54Z

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 Bot (typescript-bot) · 2025-08-27T22:23:07Z

Hey Ryan Cavanaugh (@RyanCavanaugh), the results of running the DT tests are ready.

Everything looks the same!

You can check the log here.

TypeScript Bot (typescript-bot) · 2025-08-27T22:25:39Z

Ryan Cavanaugh (@RyanCavanaugh) Here are the results of running the user tests with tsc comparing main and refs/pull/62346/merge:

There were infrastructure failures potentially unrelated to your change:

1 instance of "Git clone failed"

Otherwise...

Everything looks good!

TypeScript Bot (typescript-bot) · 2025-08-27T22:58:07Z

Ryan Cavanaugh (@RyanCavanaugh)
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 - node (v18.15.0, x64)}
_Errors	₃₄	₃₄	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_62,370	_62,370	_~	_~	_~	_{p=1.000 n=6}
_Types	_50,386	_50,386	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{194,110k (± 0.96%)}	_{194,609k (± 0.95%)}	_~	_192,918k	_196,534k	_{p=0.378 n=6}
_{Parse Time}	_{1.30s (± 0.75%)}	_{1.31s (± 0.31%)}	_~	_1.31s	_1.32s	_{p=0.056 n=6}
_{Bind Time}	_{0.73s (± 0.56%)}	_{0.73s (± 0.56%)}	_~	_0.72s	_0.73s	_{p=1.000 n=6}
_{Check Time}	_{9.76s (± 0.19%)}	_{9.76s (± 0.50%)}	_~	_9.71s	_9.84s	_{p=1.000 n=6}
_{Emit Time}	_{2.73s (± 0.80%)}	_{2.75s (± 1.38%)}	_~	_2.70s	_2.80s	_{p=0.291 n=6}
_{Total Time}	_{14.52s (± 0.20%)}	_{14.55s (± 0.47%)}	_~	_14.47s	_14.67s	_{p=0.332 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₁	₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_948,914	_948,914	_~	_~	_~	_{p=1.000 n=6}
_Types	_410,884	_410,884	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{1,246,608k (± 0.00%)}	_{1,246,637k (± 0.00%)}	_~	_1,246,581k	_1,246,682k	_{p=0.298 n=6}
_{Parse Time}	_{6.53s (± 0.99%)}	_{6.51s (± 0.91%)}	_~	_6.47s	_6.63s	_{p=0.466 n=6}
_{Bind Time}	_{1.87s (± 0.59%)}	_{1.87s (± 0.62%)}	_~	_1.85s	_1.88s	_{p=0.729 n=6}
_{Check Time}	_{32.24s (± 0.31%)}	_{32.24s (± 0.31%)}	_~	_32.14s	_32.41s	_{p=1.000 n=6}
_{Emit Time}	_{14.79s (± 0.36%)}	_{14.78s (± 0.50%)}	_~	_14.71s	_14.91s	_{p=0.517 n=6}
_{Total Time}	_{55.43s (± 0.22%)}	_{55.40s (± 0.23%)}	_~	_55.24s	_55.51s	_{p=0.936 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,545,948	_2,545,948	_~	_~	_~	_{p=1.000 n=6}
_Types	_902,562	_902,562	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,830,891k (± 0.01%)}	_{2,830,788k (± 0.00%)}	_~	_2,830,718k	_2,830,954k	_{p=0.093 n=6}
_{Parse Time}	_{8.76s (± 0.36%)}	_{8.77s (± 0.20%)}	_~	_8.75s	_8.80s	_{p=0.683 n=6}
_{Bind Time}	_{2.23s (± 0.72%)}	_{2.23s (± 0.73%)}	_~	_2.21s	_2.25s	_{p=0.934 n=6}
_{Check Time}	_{86.50s (± 1.67%)}	_{87.77s (± 0.93%)}	_~	_86.38s	_88.66s	_{p=0.066 n=6}
_{Emit Time}	_{0.62s (±124.07%)}	_{0.36s (±39.04%)}	_~	_0.30s	_0.65s	_{p=1.000 n=6}
_{Total Time}	_{98.10s (± 1.61%)}	_{99.13s (± 0.80%)}	_~	_97.70s	_99.98s	_{p=0.230 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,236,922	_1,236,923	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_259,638	_259,638	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,507,831k (±11.82%)}	_{2,447,319k (± 6.06%)}	_~	_2,386,546k	_2,750,149k	_{p=0.810 n=6}
_{Parse Time}	_{5.22s (± 1.30%)}	_{5.19s (± 1.05%)}	_~	_5.13s	_5.28s	_{p=0.748 n=6}
_{Bind Time}	_{1.81s (± 0.45%)}	_{1.80s (± 1.26%)}	_~	_1.75s	_1.81s	_{p=0.491 n=6}
_{Check Time}	_{35.17s (± 0.52%)}	_{34.97s (± 0.42%)}	_~	_34.70s	_35.11s	_{p=0.066 n=6}
_{Emit Time}	_{3.01s (± 2.54%)}	_{2.98s (± 1.23%)}	_~	_2.93s	_3.02s	_{p=0.521 n=6}
_{Total Time}	_{45.21s (± 0.46%)}	_{44.96s (± 0.33%)}	_~	_44.79s	_45.12s	_{p=0.066 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,236,922	_1,236,923	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_259,638	_259,638	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,818,872k (±14.05%)}	_{2,940,056k (±12.71%)}	_~	_2,457,031k	_3,182,171k	_{p=0.230 n=6}
_{Parse Time}	_{6.86s (± 1.08%)}	_{6.86s (± 1.78%)}	_~	_6.69s	_6.96s	_{p=1.000 n=6}
_{Bind Time}	_{2.19s (± 1.57%)}	_{2.19s (± 1.29%)}	_~	_2.16s	_2.24s	_{p=0.810 n=6}
_{Check Time}	_{42.48s (± 0.56%)}	_{42.40s (± 0.47%)}	_~	_42.16s	_42.70s	_{p=0.521 n=6}
_{Emit Time}	_{3.59s (± 4.83%)}	_{3.48s (± 0.48%)}	_~	_3.46s	_3.50s	_{p=0.470 n=6}
_{Total Time}	_{55.11s (± 0.62%)}	_{54.94s (± 0.50%)}	_~	_54.58s	_55.27s	_{p=0.298 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_262,416	_262,417	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_103,917	_103,917	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{441,719k (± 0.02%)}	_{441,676k (± 0.02%)}	_~	_441,605k	_441,776k	_{p=0.378 n=6}
_{Parse Time}	_{4.40s (± 0.87%)}	_{4.39s (± 0.84%)}	_~	_4.33s	_4.42s	_{p=0.568 n=6}
_{Bind Time}	_{1.64s (± 1.21%)}	_{1.63s (± 0.72%)}	_~	_1.62s	_1.65s	_{p=0.506 n=6}
_{Check Time}	_{23.39s (± 0.48%)}	_{23.43s (± 0.16%)}	_~	_23.38s	_23.49s	_{p=0.521 n=6}
_{Emit Time}	_{1.90s (± 0.86%)}	_{1.90s (± 0.72%)}	_~	_1.89s	_1.92s	_{p=0.564 n=6}
_{Total Time}	_{31.33s (± 0.39%)}	_{31.35s (± 0.08%)}	_~	_31.31s	_31.37s	_{p=0.374 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₇₂	₇₂	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_225,367	_225,367	_~	_~	_~	_{p=1.000 n=6}
_Types	_94,290	_94,290	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{371,153k (± 0.03%)}	_{371,212k (± 0.03%)}	_~	_371,103k	_371,454k	_{p=0.093 n=6}
_{Parse Time}	_{2.88s (± 1.31%)}	_{2.87s (± 0.84%)}	_~	_2.85s	_2.92s	_{p=0.628 n=6}
_{Bind Time}	_{1.57s (± 1.04%)}	_{1.59s (± 0.66%)}	_~	_1.58s	_1.61s	_{p=0.061 n=6}
_{Check Time}	_{16.45s (± 0.38%)}	_{16.46s (± 0.40%)}	_~	_16.38s	_16.54s	_{p=0.809 n=6}
_{Emit Time}	_{0.00s (±154.76%)}	_0.00s	_~	_~	_~	_{p=0.174 n=6}
_{Total Time}	_{20.91s (± 0.38%)}	_{20.93s (± 0.41%)}	_~	_20.83s	_21.07s	_{p=0.873 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₁	₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_3,874,623	_3,874,623	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,221,094	_1,221,094	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,701,589k (± 0.01%)}	_{3,701,741k (± 0.01%)}	_~	_3,701,252k	_3,702,002k	_{p=0.471 n=6}
_{Parse Time}	_{18.79s (± 0.50%)}	_{18.75s (± 0.35%)}	_~	_18.66s	_18.84s	_{p=0.809 n=6}
_{Bind Time}	_{6.22s (± 2.84%)}	_{6.10s (± 1.67%)}	_~	_6.03s	_6.30s	_{p=0.260 n=6}
_{Check Time}	_{126.11s (± 2.87%)}	_{127.00s (± 4.03%)}	_~	_122.01s	_133.41s	_{p=0.936 n=6}
_{Emit Time}	_{44.65s (±22.78%)}	_{44.96s (±19.89%)}	_~	_37.34s	_55.73s	_{p=0.810 n=6}
_{Total Time}	_{195.76s (± 6.85%)}	_{196.81s (± 4.42%)}	_~	_184.69s	_205.25s	_{p=0.689 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₃₇	₃₇	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_356,094	_356,094	_~	_~	_~	_{p=1.000 n=6}
_Types	_156,860	_156,860	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{513,209k (± 0.04%)}	_{513,205k (± 0.04%)}	_~	_512,919k	_513,373k	_{p=0.689 n=6}
_{Parse Time}	_{4.60s (± 0.41%)}	_{4.60s (± 0.70%)}	_~	_4.57s	_4.66s	_{p=1.000 n=6}
_{Bind Time}	_{1.90s (± 0.52%)}	_{1.91s (± 0.97%)}	_~	_1.88s	_1.93s	_{p=0.118 n=6}
_{Check Time}	_{22.05s (± 0.82%)}	_{21.92s (± 0.54%)}	_~	_21.80s	_22.13s	_{p=0.230 n=6}
_{Emit Time}	_{0.00s (±244.70%)}	_{0.00s (±244.70%)}	_~	_0.00s	_0.01s	_{p=1.000 n=6}
_{Total Time}	_{28.55s (± 0.69%)}	_{28.44s (± 0.31%)}	_~	_28.35s	_28.59s	_{p=0.378 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₃₀	₃₆	_{🔻+6 (+20.00%)}	_~	_~	_{p=0.001 n=6}
_Symbols	_666,064	_665,668	_{-396 (- 0.06%)}	_~	_~	_{p=0.001 n=6}
_Types	_199,729	_199,550	_{-179 (- 0.09%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{572,484k (± 0.03%)}	_{572,249k (± 0.02%)}	_~	_572,027k	_572,378k	_{p=0.065 n=6}
_{Parse Time}	_{5.29s (± 0.44%)}	_{5.33s (± 1.21%)}	_~	_5.22s	_5.42s	_{p=0.091 n=6}
_{Bind Time}	_{1.65s (± 0.91%)}	_{1.65s (± 0.62%)}	_~	_1.64s	_1.67s	_{p=0.867 n=6}
_{Check Time}	_{25.27s (± 1.98%)}	_{24.87s (± 1.12%)}	_~	_24.68s	_25.43s	_{p=0.229 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{32.21s (± 1.50%)}	_{31.85s (± 0.94%)}	_~	_31.66s	_32.45s	_{p=0.199 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

Compiler-Unions - node (v18.15.0, x64)
angular-1 - node (v18.15.0, x64)
mui-docs - node (v18.15.0, x64)
self-build-src - node (v18.15.0, x64)
self-build-src-public-api - node (v18.15.0, x64)
self-compiler - node (v18.15.0, x64)
ts-pre-modules - node (v18.15.0, x64)
vscode - node (v18.15.0, x64)
webpack - node (v18.15.0, x64)
xstate-main - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

TypeScript Bot (typescript-bot) · 2025-08-27T23:33:14Z

Ryan Cavanaugh (@RyanCavanaugh) Here are the results of running the top 400 repos with tsc comparing main and refs/pull/62346/merge:

Everything looks good!

…-anonymous-object-types

Ryan Cavanaugh (RyanCavanaugh) · 2025-11-05T17:19:31Z

TypeScript Bot (@typescript-bot) pack this

TypeScript Bot (typescript-bot) · 2025-11-05T17:19:37Z

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

Command	Status	Results
`pack this`	✅ Started	✅ Results

TypeScript Bot (typescript-bot) · 2025-11-05T17:24:15Z

Hey Ryan Cavanaugh (@RyanCavanaugh), I've packed this into an installable tgz. You can install it for testing by referencing it in your package.json like so:

{
"devDependencies": {
"typescript": "https://typescript.visualstudio.com/cf7ac146-d525-443c-b23c-0d58337efebc/_apis/build/builds/166456/artifacts?artifactName=tgz&fileId=FF881A7181E51FD746226C8F8B8AD2F99F484D2FAFBA4296A8441045ED0E10F602&fileName=/typescript-6.0.0-insiders.20251105.tgz"
}
}

and then running npm install.

…-anonymous-object-types

TypeScript Bot (typescript-bot) · 2026-03-24T21:22:29Z

With 6.0 out as the final release vehicle for this codebase, we're closing all PRs that don't fit the merge criteria for post-6.0 patches. If you think this was a mistake and this PR fits the post-6.0 patch criteria, please post to the 6.0 iteration issue with details (specifically, which PR and which patch criteria it satisfies).

Next steps for PRs:

For crash bugfixes or language service improvements, PRs are currently accepted at the typescript-go repo
Changes to type system behavior should wait until after 7.0, at which point mainline TypeScript development will resume in this repository with the Go codebase
Library file updates (lib.d.ts etc) continue to live in this repo or the DOM Generator repo as appropriate

Properly propagate ObjectFlags.NonInferrableType onto non-aliased a…
319249a
…nonymous object types instantiations

CopilotAI review requested due to automatic review settings August 27, 2025 21:57

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Mateusz Burzyński (Andarist) commented Aug 27, 2025
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Merge remote-tracking branch 'origin/main' into fix/silent-never-leak…
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…-anonymous-object-types

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Merge branch 'main' into fix/silent-never-leak-anonymous-object-types
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Merge remote-tracking branch 'origin/main' into fix/silent-never-leak…
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…-anonymous-object-types

TypeScript Bot (typescript-bot) closed this Mar 24, 2026

github-project-automationBot moved this from Needs merge to Done in PR Backlog Mar 24, 2026

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Properly propagate `ObjectFlags.NonInferrableType` onto non-aliased anonymous object types instantiations - #62346

Properly propagate `ObjectFlags.NonInferrableType` onto non-aliased anonymous object types instantiations#62346
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