Fixed `anyFunctionType` leak by Andarist · Pull Request #61980 · microsoft/TypeScript

Andarist · 2025-06-30T22:30:07Z

fixes #61979

Copilot

Pull Request Overview

This pull request fixes a bug that caused an anyFunctionType leak in the type checker. The changes update the contextual function checking logic and refine the checkMode usage to prevent caching of unintended return types.

Default checkMode is now explicitly provided in the function signature.
Simplified conditional checks and modified the return type computation to mask out CheckMode.SkipContextSensitive.

Reviewed Changes

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

File	Description
tests/cases/compiler/contextualTypingGenericFunction2.ts	Added tests to verify that inappropriate type inference in callback functions is now caught.
tests/baselines/reference/contextualTypingGenericFunction2.*	Updated baselines to match the expected errors from the fixed type checking logic.
src/compiler/checker.ts	Updated contextuallyCheckFunctionExpressionOrObjectLiteralMethod to use default checkMode and fixed return type computation to avoid caching anyFunctionType leaks.

Comments suppressed due to low confidence (4)

src/compiler/checker.ts:9115

Removing the redundant existence check for checkMode improves readability now that a default is provided.

) {

src/compiler/checker.ts:9115

The explicit default value for checkMode enhances clarity; please ensure that existing call sites behave correctly with this default.

) {

src/compiler/checker.ts:9115

The simplified condition using checkMode enhances consistency with previous changes; ensure the logical behavior remains as expected.

) {

jakebailey · 2025-06-30T22:31:23Z

@typescript-bot test it

typescript-bot · 2025-06-30T22:31:29Z

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 · 2025-06-30T22:53:22Z

Hey @jakebailey, the results of running the DT tests are ready.

Everything looks the same!

You can check the log here.

typescript-bot · 2025-06-30T22:57:51Z

@jakebailey Here are the results of running the user tests with tsc comparing main and refs/pull/61980/merge:

Everything looks good!

typescript-bot · 2025-06-30T23:15:47Z

@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 - 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}	_{194,759k (± 1.03%)}	_{195,995k (± 0.73%)}	_~	_193,078k	_196,692k	_{p=0.173 n=6}
_{Parse Time}	_{1.60s (± 1.51%)}	_{1.60s (± 0.92%)}	_~	_1.58s	_1.62s	_{p=0.459 n=6}
_{Bind Time}	_{0.88s (± 2.03%)}	_{0.87s (± 1.92%)}	_~	_0.84s	_0.89s	_{p=0.285 n=6}
_{Check Time}	_{11.80s (± 0.79%)}	_{11.83s (± 0.76%)}	_~	_11.70s	_11.93s	_{p=0.686 n=6}
_{Emit Time}	_{3.34s (± 3.76%)}	_{3.33s (± 3.48%)}	_~	_3.25s	_3.56s	_{p=1.000 n=6}
_{Total Time}	_{17.62s (± 0.94%)}	_{17.64s (± 0.64%)}	_~	_17.47s	_17.78s	_{p=0.630 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₅₆	₅₆	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_948,753	_948,753	_~	_~	_~	_{p=1.000 n=6}
_Types	_410,846	_410,846	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{1,225,228k (± 0.00%)}	_{1,225,209k (± 0.00%)}	_~	_1,225,181k	_1,225,231k	_{p=0.470 n=6}
_{Parse Time}	_{7.93s (± 0.60%)}	_{7.94s (± 0.56%)}	_~	_7.88s	_7.99s	_{p=0.747 n=6}
_{Bind Time}	_{2.27s (± 0.72%)}	_{2.26s (± 0.46%)}	_~	_2.25s	_2.28s	_{p=0.210 n=6}
_{Check Time}	_{37.91s (± 0.48%)}	_{37.91s (± 0.22%)}	_~	_37.74s	_37.97s	_{p=0.688 n=6}
_{Emit Time}	_{17.77s (± 0.40%)}	_{17.78s (± 0.55%)}	_~	_17.61s	_17.90s	_{p=0.375 n=6}
_{Total Time}	_{65.88s (± 0.30%)}	_{65.89s (± 0.18%)}	_~	_65.69s	_66.02s	_{p=1.000 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,509,183	_2,509,183	_~	_~	_~	_{p=1.000 n=6}
_Types	_892,716	_892,716	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,804,395k (± 0.01%)}	_{2,804,479k (± 0.00%)}	_~	_2,804,337k	_2,804,557k	_{p=0.810 n=6}
_{Parse Time}	_{10.50s (± 0.35%)}	_{10.50s (± 0.48%)}	_~	_10.45s	_10.58s	_{p=1.000 n=6}
_{Bind Time}	_{2.73s (± 0.55%)}	_{2.74s (± 0.72%)}	_~	_2.72s	_2.77s	_{p=0.934 n=6}
_{Check Time}	_{101.98s (± 1.24%)}	_{101.21s (± 0.29%)}	_~	_100.64s	_101.45s	_{p=0.689 n=6}
_{Emit Time}	_{0.78s (±129.01%)}	_{0.37s (± 2.67%)}	_~	_0.36s	_0.38s	_{p=0.611 n=6}
_{Total Time}	_{115.99s (± 1.77%)}	_{114.81s (± 0.28%)}	_~	_114.19s	_115.10s	_{p=0.810 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,227,081	_1,227,081	_~	_~	_~	_{p=1.000 n=6}
_Types	_267,474	_267,474	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,730,873k (±14.64%)}	_{2,731,389k (±14.64%)}	_~	_2,365,119k	_3,097,551k	_{p=0.575 n=6}
_{Parse Time}	_{6.64s (± 1.19%)}	_{6.60s (± 1.66%)}	_~	_6.46s	_6.73s	_{p=0.630 n=6}
_{Bind Time}	_{2.16s (± 1.30%)}	_{2.19s (± 1.57%)}	_~	_2.15s	_2.23s	_{p=0.253 n=6}
_{Check Time}	_{42.63s (± 0.32%)}	_{42.84s (± 0.53%)}	_~	_42.51s	_43.17s	_{p=0.065 n=6}
_{Emit Time}	_{3.55s (± 4.31%)}	_{3.44s (± 0.95%)}	_{🟩-0.11s (- 3.05%)}	_3.40s	_3.48s	_{p=0.045 n=6}
_{Total Time}	_{54.99s (± 0.26%)}	_{55.06s (± 0.53%)}	_~	_54.66s	_55.44s	_{p=0.810 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,227,081	_1,227,081	_~	_~	_~	_{p=1.000 n=6}
_Types	_267,474	_267,474	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,039,830k (± 9.78%)}	_{2,918,915k (±12.90%)}	_~	_2,431,851k	_3,163,406k	_{p=0.810 n=6}
_{Parse Time}	_{6.92s (± 1.40%)}	_{6.86s (± 1.63%)}	_~	_6.67s	_6.95s	_{p=0.423 n=6}
_{Bind Time}	_{2.18s (± 1.57%)}	_{2.16s (± 2.18%)}	_~	_2.11s	_2.22s	_{p=0.520 n=6}
_{Check Time}	_{42.85s (± 0.63%)}	_{43.06s (± 0.27%)}	_~	_42.90s	_43.23s	_{p=0.128 n=6}
_{Emit Time}	_{3.54s (± 2.72%)}	_{3.60s (± 0.54%)}	_~	_3.58s	_3.63s	_{p=0.470 n=6}
_{Total Time}	_{55.48s (± 0.65%)}	_{55.67s (± 0.15%)}	_~	_55.58s	_55.80s	_{p=0.470 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_262,548	_262,548	_~	_~	_~	_{p=1.000 n=6}
_Types	_107,156	_107,156	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{441,957k (± 0.02%)}	_{441,912k (± 0.02%)}	_~	_441,851k	_442,049k	_{p=0.298 n=6}
_{Parse Time}	_{3.52s (± 0.71%)}	_{3.52s (± 0.79%)}	_~	_3.47s	_3.55s	_{p=1.000 n=6}
_{Bind Time}	_{1.33s (± 1.00%)}	_{1.32s (± 1.35%)}	_~	_1.29s	_1.34s	_{p=0.458 n=6}
_{Check Time}	_{18.88s (± 0.29%)}	_{18.89s (± 0.32%)}	_~	_18.78s	_18.94s	_{p=0.574 n=6}
_{Emit Time}	_{1.53s (± 1.09%)}	_{1.52s (± 0.97%)}	_~	_1.50s	_1.54s	_{p=0.560 n=6}
_{Total Time}	_{25.26s (± 0.36%)}	_{25.25s (± 0.23%)}	_~	_25.18s	_25.32s	_{p=0.872 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₇₁	₇₁	_~	_~	_~	_{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}	_{371,137k (± 0.03%)}	_{371,265k (± 0.08%)}	_~	_371,099k	_371,887k	_{p=0.261 n=6}
_{Parse Time}	_{3.58s (± 0.72%)}	_{3.59s (± 0.53%)}	_~	_3.57s	_3.61s	_{p=1.000 n=6}
_{Bind Time}	_{1.97s (± 0.87%)}	_{1.98s (± 0.95%)}	_~	_1.95s	_2.00s	_{p=0.627 n=6}
_{Check Time}	_{20.32s (± 0.25%)}	_{20.31s (± 0.33%)}	_~	_20.22s	_20.43s	_{p=0.687 n=6}
_{Emit Time}	_0.00s	_{0.00s (±244.70%)}	_~	_0.00s	_0.01s	_{p=0.405 n=6}
_{Total Time}	_{25.87s (± 0.26%)}	_{25.88s (± 0.30%)}	_~	_25.78s	_25.99s	_{p=1.000 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₃₃	₃₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_3,499,297	_3,499,297	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,177,214	_1,177,214	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,549,841k (± 0.01%)}	_{3,549,767k (± 0.01%)}	_~	_3,549,455k	_3,550,012k	_{p=0.378 n=6}
_{Parse Time}	_{14.98s (± 0.41%)}	_{15.00s (± 0.31%)}	_~	_14.94s	_15.08s	_{p=0.747 n=6}
_{Bind Time}	_{4.90s (± 0.60%)}	_{4.89s (± 0.42%)}	_~	_4.86s	_4.92s	_{p=1.000 n=6}
_{Check Time}	_{95.52s (± 3.15%)}	_{96.59s (± 4.04%)}	_~	_93.48s	_101.82s	_{p=0.936 n=6}
_{Emit Time}	_{30.04s (± 2.34%)}	_{30.65s (± 4.07%)}	_~	_29.64s	_32.81s	_{p=0.173 n=6}
_{Total Time}	_{145.44s (± 2.39%)}	_{147.13s (± 2.89%)}	_~	_143.75s	_152.75s	_{p=0.471 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_318,019	_318,019	_~	_~	_~	_{p=1.000 n=6}
_Types	_137,705	_137,705	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{472,012k (± 0.01%)}	_{471,991k (± 0.01%)}	_~	_471,908k	_472,090k	_{p=0.688 n=6}
_{Parse Time}	_{3.58s (± 0.41%)}	_{3.59s (± 0.58%)}	_~	_3.55s	_3.61s	_{p=0.373 n=6}
_{Bind Time}	_{1.44s (± 0.68%)}	_{1.43s (± 0.73%)}	_~	_1.42s	_1.45s	_{p=0.673 n=6}
_{Check Time}	_{17.38s (± 0.39%)}	_{17.36s (± 0.41%)}	_~	_17.26s	_17.46s	_{p=0.688 n=6}
_{Emit Time}	_{0.00s (±244.70%)}	_0.00s	_~	_~	_~	_{p=0.405 n=6}
_{Total Time}	_{22.40s (± 0.26%)}	_{22.38s (± 0.41%)}	_~	_22.27s	_22.52s	_{p=0.568 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₃₀	₃₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_665,978	_665,978	_~	_~	_~	_{p=1.000 n=6}
_Types	_199,345	_199,345	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{570,269k (± 0.03%)}	_{570,339k (± 0.02%)}	_~	_570,088k	_570,480k	_{p=0.748 n=6}
_{Parse Time}	_{4.24s (± 0.50%)}	_{4.25s (± 0.73%)}	_~	_4.20s	_4.28s	_{p=0.806 n=6}
_{Bind Time}	_{1.33s (± 0.41%)}	_{1.33s (± 0.67%)}	_~	_1.32s	_1.34s	_{p=0.341 n=6}
_{Check Time}	_{20.01s (± 0.98%)}	_{19.99s (± 1.67%)}	_~	_19.77s	_20.66s	_{p=0.471 n=6}
_{Emit Time}	_{0.00s (±244.70%)}	_{0.00s (±244.70%)}	_~	_0.00s	_0.01s	_{p=1.000 n=6}
_{Total Time}	_{25.60s (± 0.84%)}	_{25.56s (± 1.35%)}	_~	_25.36s	_26.26s	_{p=0.471 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 · 2025-07-01T00:15:08Z

@jakebailey Here are the results of running the top 400 repos with tsc comparing main and refs/pull/61980/merge:

Everything looks good!

…-leak

jakebailey · 2025-12-05T18:58:40Z

This feels plausible, but I find it surprising that we haven't used this trick elsewhere?

Andarist · 2025-12-05T19:21:27Z

This leak is quite specific to generic functions containing context-sensitive parts when other parts of the argument(s) are context-sensitive too.

The problem is that the generic function itself is not treated as context-sensitive per-se (despite it containing context-sensitive functions inside it) so without other context-sensitive parts of the arguments the initial argCheckMode stays as CheckMode.Normal. In that scenario, only a single inference pass happens and the inner context-sensitive function gets resolved correctly.

But in the other situation, the argCheckMode gets set to CheckMode.SkipContextSensitive and if that gets propagate to the inner context-sensitive function, its return type gets cached incorrectly. Remember that its being cached while checking a supposedly non-context sensitive parent - whereas normally, a parent is always~ context-sensitive when it contains context-sensitive descendants as that "trait" propagates from descandants to ancestors.

Fixed anyFunctionType leak

0c0ec83

Copilot AI review requested due to automatic review settings June 30, 2025 22:30

github-project-automation bot added this to PR Backlog Jun 30, 2025

github-project-automation bot moved this to Not started in PR Backlog Jun 30, 2025

typescript-bot added the For Uncommitted Bug PR for untriaged, rejected, closed or missing bug label Jun 30, 2025

Copilot AI reviewed Jun 30, 2025

View reviewed changes

RyanCavanaugh requested a review from ahejlsberg July 7, 2025 19:01

Merge remote-tracking branch 'origin/main' into fix/any-function-type…

3785888

…-leak

typescript-bot added For Backlog Bug PRs that fix a backlog bug and removed For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Dec 5, 2025

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Fixed `anyFunctionType` leak#61980

Fixed `anyFunctionType` leak#61980
Andarist wants to merge 2 commits intomicrosoft:mainfrom
Andarist:fix/any-function-type-leak

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