Port anyFunctionType subtype fix and JSX children NonInferrableType propagation from typescript-go by Copilot · Pull Request #63163 · microsoft/TypeScript

Copilot · 2026-02-19T23:12:31Z

Ports two fixes from typescript-go:

Make anyFunctionType a subtype of all function types typescript-go#1149 — Make anyFunctionType a subtype of all function types
Fixed JSX context-sensitive children discrimination for generic signatures typescript-go#2803 — Fixed JSX context-sensitive children discrimination for generic signatures

`anyFunctionType` subtype relation

In signaturesRelatedTo, anyFunctionType was treated symmetrically—both as source and target it returned Ternary.True. This caused incorrect subtype reduction: when a union included anyFunctionType alongside a real function type, the real type could be reduced away instead of the wildcard.

Now anyFunctionType is a proper subtype (source → True) but not a supertype (target → False). This fixes inference in patterns like:

declare function useMemo<T>(func: () => T): T;

const predicate = useMemo(() => {
    if (cond) return () => true;    // anyFunctionType
    return x => x.length > 0;      // previously inferred x: string, now correctly x: any + TS7006
});

JSX children `NonInferrableType` propagation

When building the JSX attributes spread type for children, getPropagatingFlagsOfTypes(childrenTypes) was not included in the objectFlags passed to getSpreadType. This meant the NonInferrableType flag from anyFunctionType children wasn't propagated, breaking context-sensitive discrimination for generic JSX component signatures.

// children as JSX body now correctly infers `selected: number`
<TestComponent state={{ foo: 123 }} selector={(state) => state.foo}>
  {(selected) => <div>{Math.max(selected, 0)}</div>}
</TestComponent>

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

…NonInferrableType propagation Co-authored-by: DanielRosenwasser <972891+DanielRosenwasser@users.noreply.github.com>

DanielRosenwasser · 2026-02-19T23:38:36Z

@typescript-bot test this

typescript-bot · 2026-02-19T23:38:40Z

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

Ports two TypeScript type-checker fixes from typescript-go into the main compiler: (1) correct subtype reduction behavior involving the internal anyFunctionType wildcard, and (2) ensure JSX children spread types propagate NonInferrableType so context-sensitive discrimination works for generic JSX component signatures.

Changes:

Update signature relatedness so anyFunctionType is treated as a subtype (source) but not as a supertype (target) of other function types.
Propagate getPropagatingFlagsOfTypes(childrenTypes) into the object flags passed to getSpreadType when synthesizing JSX children.
Add new compiler regression tests and reference baselines covering the subtype reduction and JSX children inference scenarios.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/compiler/checker.ts	Adjusts `anyFunctionType` signature relatedness semantics; propagates children flags (incl. `NonInferrableType`) into JSX children spread typing.
tests/cases/compiler/subtypeReductionWithAnyFunctionType.ts	New regression test for union subtype reduction involving `anyFunctionType`, ensuring real function types aren’t incorrectly reduced away.
tests/baselines/reference/subtypeReductionWithAnyFunctionType.types	Type baseline validating inferred types (notably the `any` parameter) for the new subtype reduction test.
tests/baselines/reference/subtypeReductionWithAnyFunctionType.symbols	Symbols baseline for the new subtype reduction test.
tests/baselines/reference/subtypeReductionWithAnyFunctionType.errors.txt	Error baseline asserting the expected TS7006 implicit-`any` diagnostic.
tests/cases/compiler/jsxFunctionTypeChildren.tsx	New regression test ensuring JSX children function typing behaves like the equivalent non-JSX call in a generic props scenario.
tests/baselines/reference/jsxFunctionTypeChildren.types	Type baseline for the JSX children function typing test.
tests/baselines/reference/jsxFunctionTypeChildren.symbols	Symbols baseline for the JSX children function typing test.
tests/cases/compiler/contextuallyTypedJsxChildren2.tsx	New regression test for context-sensitive JSX children discrimination with generic signatures (children-body vs non-children prop).
tests/baselines/reference/contextuallyTypedJsxChildren2.types	Type baseline validating correct inference (e.g. `selected: number`) for the JSX discrimination test.
tests/baselines/reference/contextuallyTypedJsxChildren2.symbols	Symbols baseline for the JSX discrimination test.

typescript-bot · 2026-02-19T23:54:21Z

Hey @DanielRosenwasser, it looks like the DT test run failed. Please check the log for more details.

You can check the log here.

jakebailey · 2026-02-20T00:04:51Z

@typescript-bot run dt

typescript-bot · 2026-02-20T00:04:55Z

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

Command	Status	Results
`run dt`	✅ Started	❌ Results

typescript-bot · 2026-02-20T00:05:48Z

@DanielRosenwasser Here are the results of running the user tests with tsc comparing main and refs/pull/63163/merge:

There were infrastructure failures potentially unrelated to your change:

1 instance of "Git clone failed"

Otherwise...

Everything looks good!

typescript-bot · 2026-02-20T00:21:48Z

Hey @jakebailey, it looks like the DT test run failed. Please check the log for more details.

You can check the log here.

typescript-bot · 2026-02-20T00:47:16Z

@DanielRosenwasser
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	₃	₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_82,521	_82,521	_~	_~	_~	_{p=1.000 n=6}
_Types	_125,280	_125,280	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{275,082k (± 0.50%)}	_{276,155k (± 0.67%)}	_~	_274,428k	_277,929k	_{p=0.471 n=6}
_{Parse Time}	_{1.30s (± 0.42%)}	_{1.30s (± 0.63%)}	_~	_1.29s	_1.31s	_{p=0.859 n=6}
_{Bind Time}	_{0.76s (± 0.68%)}	_{0.75s (± 0.68%)}	_~	_0.75s	_0.76s	_{p=0.311 n=6}
_{Check Time}	_{14.16s (± 0.41%)}	_{14.15s (± 0.50%)}	_~	_14.04s	_14.25s	_{p=1.000 n=6}
_{Emit Time}	_{2.67s (± 0.39%)}	_{2.66s (± 0.61%)}	_~	_2.64s	_2.68s	_{p=1.000 n=6}
_{Total Time}	_{18.88s (± 0.31%)}	_{18.87s (± 0.36%)}	_~	_18.77s	_18.97s	_{p=1.000 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_959,126	_959,126	_~	_~	_~	_{p=1.000 n=6}
_Types	_416,034	_416,034	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{1,260,822k (± 0.00%)}	_{1,260,855k (± 0.00%)}	_~	_1,260,780k	_1,260,915k	_{p=0.298 n=6}
_{Parse Time}	_{6.51s (± 0.48%)}	_{6.55s (± 0.63%)}	_~	_6.50s	_6.62s	_{p=0.221 n=6}
_{Bind Time}	_{1.97s (± 0.38%)}	_{1.97s (± 0.21%)}	_~	_1.97s	_1.98s	_{p=0.389 n=6}
_{Check Time}	_{32.45s (± 0.28%)}	_{32.34s (± 0.29%)}	_~	_32.19s	_32.48s	_{p=0.065 n=6}
_{Emit Time}	_{15.09s (± 0.35%)}	_{15.07s (± 0.36%)}	_~	_15.01s	_15.17s	_{p=0.518 n=6}
_{Total Time}	_{56.02s (± 0.25%)}	_{55.92s (± 0.17%)}	_~	_55.83s	_56.04s	_{p=0.378 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	_11,439	_11,439	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,706,620	_2,706,879	_{+259 (+ 0.01%)}	_~	_~	_{p=0.001 n=6}
_Types	_931,168	_931,241	_{+73 (+ 0.01%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{3,046,078k (± 0.00%)}	_{3,046,217k (± 0.01%)}	_~	_3,046,108k	_3,046,500k	_{p=0.066 n=6}
_{Parse Time}	_{8.53s (± 0.29%)}	_{8.53s (± 0.35%)}	_~	_8.47s	_8.55s	_{p=0.685 n=6}
_{Bind Time}	_{2.31s (± 0.42%)}	_{2.32s (± 0.18%)}	_~	_2.32s	_2.33s	_{p=0.056 n=6}
_{Check Time}	_{95.50s (± 0.60%)}	_{95.42s (± 0.39%)}	_~	_95.10s	_95.93s	_{p=0.873 n=6}
_{Emit Time}	_{0.32s (± 1.97%)}	_{0.32s (± 2.34%)}	_~	_0.31s	_0.33s	_{p=0.718 n=6}
_{Total Time}	_{106.66s (± 0.53%)}	_{106.59s (± 0.33%)}	_~	_106.28s	_107.05s	_{p=0.936 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,253,407	_1,253,407	_~	_~	_~	_{p=1.000 n=6}
_Types	_260,208	_260,208	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,396,837k (± 0.04%)}	_{2,518,404k (±11.85%)}	_~	_2,395,920k	_3,128,223k	_{p=0.810 n=6}
_{Parse Time}	_{5.19s (± 1.45%)}	_{5.18s (± 1.41%)}	_~	_5.11s	_5.29s	_{p=1.000 n=6}
_{Bind Time}	_{1.87s (± 0.55%)}	_{1.84s (± 1.27%)}	_{-0.03s (- 1.61%)}	_1.81s	_1.87s	_{p=0.041 n=6}
_{Check Time}	_{35.69s (± 0.28%)}	_{35.69s (± 0.48%)}	_~	_35.50s	_35.98s	_{p=0.936 n=6}
_{Emit Time}	_{2.99s (± 1.21%)}	_{3.02s (± 2.75%)}	_~	_2.92s	_3.13s	_{p=0.471 n=6}
_{Total Time}	_{45.77s (± 0.36%)}	_{45.76s (± 0.41%)}	_~	_45.49s	_46.02s	_{p=0.873 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,253,407	_1,253,407	_~	_~	_~	_{p=1.000 n=6}
_Types	_260,208	_260,208	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,073,635k (± 9.65%)}	_{3,072,946k (± 9.66%)}	_~	_2,466,271k	_3,194,475k	_{p=0.471 n=6}
_{Parse Time}	_{8.44s (± 1.65%)}	_{8.43s (± 1.43%)}	_~	_8.23s	_8.58s	_{p=0.936 n=6}
_{Bind Time}	_{2.74s (± 1.68%)}	_{2.77s (± 1.27%)}	_~	_2.73s	_2.83s	_{p=0.108 n=6}
_{Check Time}	_{53.56s (± 0.46%)}	_{53.37s (± 0.17%)}	_~	_53.28s	_53.53s	_{p=0.093 n=6}
_{Emit Time}	_{4.36s (± 1.51%)}	_{4.33s (± 2.01%)}	_~	_4.23s	_4.42s	_{p=0.810 n=6}
_{Total Time}	_{69.11s (± 0.53%)}	_{68.91s (± 0.32%)}	_~	_68.58s	_69.12s	_{p=0.297 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_265,173	_265,173	_~	_~	_~	_{p=1.000 n=6}
_Types	_104,282	_104,282	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{444,507k (± 0.02%)}	_{444,537k (± 0.01%)}	_~	_444,466k	_444,624k	_{p=0.936 n=6}
_{Parse Time}	_{3.52s (± 1.40%)}	_{3.52s (± 0.83%)}	_~	_3.48s	_3.57s	_{p=1.000 n=6}
_{Bind Time}	_{1.38s (± 0.79%)}	_{1.37s (± 1.41%)}	_~	_1.36s	_1.41s	_{p=0.187 n=6}
_{Check Time}	_{19.29s (± 0.35%)}	_{19.28s (± 0.38%)}	_~	_19.21s	_19.41s	_{p=0.810 n=6}
_{Emit Time}	_{1.54s (± 0.68%)}	_{1.55s (± 1.29%)}	_~	_1.53s	_1.58s	_{p=1.000 n=6}
_{Total Time}	_{25.73s (± 0.44%)}	_{25.73s (± 0.22%)}	_~	_25.67s	_25.82s	_{p=0.810 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₂₇₁	₂₇₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_225,883	_225,883	_~	_~	_~	_{p=1.000 n=6}
_Types	_93,564	_93,564	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{371,591k (± 0.02%)}	_{371,612k (± 0.01%)}	_~	_371,568k	_371,647k	_{p=0.230 n=6}
_{Parse Time}	_{2.86s (± 0.57%)}	_{2.83s (± 1.38%)}	_~	_2.76s	_2.87s	_{p=0.089 n=6}
_{Bind Time}	_{1.63s (± 1.58%)}	_{1.63s (± 1.38%)}	_~	_1.59s	_1.66s	_{p=0.803 n=6}
_{Check Time}	_{17.46s (± 0.35%)}	_{17.46s (± 0.41%)}	_~	_17.38s	_17.57s	_{p=0.936 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{21.96s (± 0.18%)}	_{21.92s (± 0.37%)}	_~	_21.81s	_22.04s	_{p=0.332 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₅₇	₅₇	_~	_~	_~	_{p=1.000 n=5+6}
_Symbols	_4,359,723	_4,359,721	_{-2 (- 0.00%)}	_~	_~	_{p=0.002 n=5+6}
_Types	_1,386,348	_1,386,348	_~	_~	_~	_{p=1.000 n=5+6}
_{Memory used}	_{4,162,029k (± 0.01%)}	_{4,162,113k (± 0.00%)}	_~	_4,161,912k	_4,162,318k	_{p=0.411 n=5+6}
_{Parse Time}	_{16.67s (± 0.70%)}	_{16.66s (± 0.75%)}	_~	_16.54s	_16.86s	_{p=0.855 n=5+6}
_{Bind Time}	_{5.67s (± 1.15%)}	_{5.64s (± 0.29%)}	_~	_5.62s	_5.66s	_{p=0.167 n=5+6}
_{Check Time}	_{138.15s (± 2.79%)}	_{142.66s (± 3.94%)}	_~	_134.85s	_148.92s	_{p=0.235 n=5+6}
_{Emit Time}	_{88.34s (± 4.34%)}	_{88.31s (± 4.40%)}	_~	_84.49s	_92.23s	_{p=0.784 n=5+6}
_{Total Time}	_{248.82s (± 1.90%)}	_{253.28s (± 1.42%)}	_~	_249.58s	_258.99s	_{p=0.055 n=5+6}
_{webpack - node (v18.15.0, x64)}
_Errors	₄₁	₄₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_407,330	_407,330	_~	_~	_~	_{p=1.000 n=6}
_Types	_186,189	_186,189	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{568,814k (± 0.01%)}	_{568,750k (± 0.01%)}	_~	_568,667k	_568,794k	_{p=0.128 n=6}
_{Parse Time}	_{4.81s (± 0.61%)}	_{4.78s (± 0.45%)}	_~	_4.75s	_4.81s	_{p=0.124 n=6}
_{Bind Time}	_{2.04s (± 1.79%)}	_{2.04s (± 1.05%)}	_~	_2.01s	_2.06s	_{p=1.000 n=6}
_{Check Time}	_{24.66s (± 0.26%)}	_{24.47s (± 0.60%)}	_{-0.20s (- 0.79%)}	_24.22s	_24.63s	_{p=0.013 n=6}
_{Emit Time}	_{0.00s (±154.76%)}	_{0.00s (±154.76%)}	_~	_0.00s	_0.01s	_{p=1.000 n=6}
_{Total Time}	_{31.52s (± 0.26%)}	_{31.30s (± 0.50%)}	_{-0.22s (- 0.70%)}	_31.03s	_31.47s	_{p=0.013 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₃₀	₃₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_764,198	_764,198	_~	_~	_~	_{p=1.000 n=6}
_Types	_219,050	_219,050	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{684,903k (± 0.01%)}	_{684,850k (± 0.01%)}	_~	_684,762k	_684,948k	_{p=0.173 n=6}
_{Parse Time}	_{4.89s (± 0.83%)}	_{4.92s (± 0.73%)}	_~	_4.87s	_4.97s	_{p=0.146 n=6}
_{Bind Time}	_{1.57s (± 0.48%)}	_{1.59s (± 1.05%)}	_~	_1.57s	_1.61s	_{p=0.080 n=6}
_{Check Time}	_{22.56s (± 0.52%)}	_{22.60s (± 0.53%)}	_~	_22.47s	_22.75s	_{p=0.748 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{29.02s (± 0.42%)}	_{29.11s (± 0.39%)}	_~	_28.99s	_29.30s	_{p=0.261 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 · 2026-02-20T00:57:35Z

@DanielRosenwasser Here are the results of running the top 400 repos with tsc comparing main and refs/pull/63163/merge:

Everything looks good!

Initial plan

70a2884

Copilot AI assigned Copilot and DanielRosenwasser Feb 19, 2026

typescript-bot added For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Feb 19, 2026

Copilot started work on behalf of DanielRosenwasser February 19, 2026 23:12 View session

Port typescript-go PRs: anyFunctionType subtype fix and JSX children …

0a50086

…NonInferrableType propagation Co-authored-by: DanielRosenwasser <972891+DanielRosenwasser@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Port changes from multiple PRs on function types and JSX~~ Port anyFunctionType subtype fix and JSX children NonInferrableType propagation from typescript-go Feb 19, 2026

Copilot finished work on behalf of DanielRosenwasser February 19, 2026 23:32

Copilot AI requested a review from DanielRosenwasser February 19, 2026 23:32

DanielRosenwasser marked this pull request as ready for review February 19, 2026 23:38

DanielRosenwasser requested review from ahejlsberg, Copilot and jakebailey February 19, 2026 23:38

Copilot started reviewing on behalf of DanielRosenwasser February 19, 2026 23:39 View session

Copilot AI reviewed Feb 19, 2026

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DanielRosenwasser mentioned this pull request Feb 20, 2026

Difference in typechecking results for a TSX file in 7.0.0-dev.20260218.1 and later microsoft/typescript-go#2843

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Port anyFunctionType subtype fix and JSX children NonInferrableType propagation from typescript-go#63163

Port anyFunctionType subtype fix and JSX children NonInferrableType propagation from typescript-go#63163
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`anyFunctionType` subtype relation

JSX children `NonInferrableType` propagation

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