Fixed instantiation expression type param leak in body-less arrows by Andarist · Pull Request #61054 · microsoft/TypeScript

Andarist · 2025-01-26T23:32:06Z

Andarist · 2025-01-26T23:40:39Z

+export const test1 = <X,>(g: <A>(x: X) => X) => g<string>;
+export const output1 = test1<number>((y: number) => 1);
+output1(1);


The leaked type param was filtered out by the call to isTypeParameterPossiblyReferenced in getObjectTypeInstantiation. It was crucial for the bug that a body-less arrow function returned the instantiation expression. With a block function body isTypeParameterPossiblyReferenced would already return true.

jakebailey · 2025-01-27T04:18:52Z

@typescript-bot test it

typescript-bot · 2025-01-27T04:18:56Z

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 · 2025-01-27T04:40:06Z

@jakebailey Here are the results of running the user tests with tsc comparing main and refs/pull/61054/merge:

Everything looks good!

typescript-bot · 2025-01-27T04:41:43Z

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

Everything looks the same!

You can check the log here.

typescript-bot · 2025-01-27T05:09:35Z

@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	_62,390	_62,390	_~	_~	_~	_{p=1.000 n=6}
_Types	_50,395	_50,395	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{193,852k (± 0.73%)}	_{194,933k (± 0.95%)}	_~	_193,125k	_196,957k	_{p=0.261 n=6}
_{Parse Time}	_{1.30s (± 1.43%)}	_{1.30s (± 1.06%)}	_~	_1.28s	_1.32s	_{p=0.867 n=6}
_{Bind Time}	_0.73s	_0.73s	_~	_~	_~	_{p=1.000 n=6}
_{Check Time}	_{9.75s (± 0.32%)}	_{9.74s (± 0.62%)}	_~	_9.66s	_9.84s	_{p=0.870 n=6}
_{Emit Time}	_{2.71s (± 0.60%)}	_{2.72s (± 0.60%)}	_~	_2.70s	_2.74s	_{p=0.330 n=6}
_{Total Time}	_{14.49s (± 0.29%)}	_{14.50s (± 0.40%)}	_~	_14.42s	_14.59s	_{p=1.000 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₃₇	₃₇	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_948,493	_948,493	_~	_~	_~	_{p=1.000 n=6}
_Types	_411,005	_411,005	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{1,225,417k (± 0.00%)}	_{1,225,398k (± 0.00%)}	_~	_1,225,353k	_1,225,448k	_{p=0.336 n=6}
_{Parse Time}	_{6.65s (± 0.52%)}	_{6.67s (± 0.15%)}	_~	_6.66s	_6.68s	_{p=0.091 n=6}
_{Bind Time}	_{1.88s (± 0.62%)}	_{1.90s (± 0.47%)}	_{+0.02s (+ 0.97%)}	_1.89s	_1.91s	_{p=0.027 n=6}
_{Check Time}	_{31.99s (± 0.44%)}	_{31.91s (± 0.25%)}	_~	_31.79s	_32.04s	_{p=0.422 n=6}
_{Emit Time}	_{15.24s (± 0.41%)}	_{15.21s (± 0.28%)}	_~	_15.12s	_15.23s	_{p=0.226 n=6}
_{Total Time}	_{55.76s (± 0.27%)}	_{55.69s (± 0.14%)}	_~	_55.58s	_55.80s	_{p=0.378 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,447,301	_2,447,301	_~	_~	_~	_{p=1.000 n=6}
_Types	_898,516	_898,516	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,307,984k (± 0.00%)}	_{2,308,042k (± 0.00%)}	_~	_2,307,939k	_2,308,079k	_{p=0.173 n=6}
_{Parse Time}	_{8.94s (± 0.24%)}	_{8.93s (± 0.24%)}	_~	_8.90s	_8.95s	_{p=0.416 n=6}
_{Bind Time}	_{2.17s (± 0.47%)}	_{2.18s (± 0.19%)}	_~	_2.17s	_2.18s	_{p=0.257 n=6}
_{Check Time}	_{74.38s (± 0.55%)}	_{74.29s (± 0.16%)}	_~	_74.09s	_74.40s	_{p=0.575 n=6}
_{Emit Time}	_{0.28s (± 2.26%)}	_{0.28s (± 2.67%)}	_~	_0.27s	_0.29s	_{p=0.718 n=6}
_{Total Time}	_{85.77s (± 0.47%)}	_{85.68s (± 0.14%)}	_~	_85.45s	_85.81s	_{p=0.521 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,229,397	_1,229,398	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_267,085	_267,086	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,362,458k (± 0.03%)}	_{2,362,656k (± 0.02%)}	_~	_2,362,074k	_2,363,178k	_{p=1.000 n=6}
_{Parse Time}	_{5.22s (± 0.59%)}	_{5.24s (± 0.58%)}	_~	_5.19s	_5.27s	_{p=0.336 n=6}
_{Bind Time}	_{1.79s (± 0.96%)}	_{1.80s (± 0.77%)}	_~	_1.78s	_1.82s	_{p=0.738 n=6}
_{Check Time}	_{35.22s (± 0.20%)}	_{35.24s (± 0.45%)}	_~	_34.98s	_35.47s	_{p=0.575 n=6}
_{Emit Time}	_{3.00s (± 1.22%)}	_{3.00s (± 0.69%)}	_~	_2.97s	_3.03s	_{p=0.686 n=6}
_{Total Time}	_{45.24s (± 0.19%)}	_{45.27s (± 0.33%)}	_~	_45.00s	_45.46s	_{p=0.423 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,229,397	_1,229,398	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_267,085	_267,086	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,796,207k (±14.22%)}	_{2,795,945k (±14.22%)}	_~	_2,432,269k	_3,159,523k	_{p=0.936 n=6}
_{Parse Time}	_{6.93s (± 1.40%)}	_{6.91s (± 1.71%)}	_~	_6.73s	_7.07s	_{p=0.810 n=6}
_{Bind Time}	_{2.16s (± 1.30%)}	_{2.18s (± 1.42%)}	_~	_2.13s	_2.21s	_{p=0.333 n=6}
_{Check Time}	_{42.82s (± 0.67%)}	_{42.79s (± 0.52%)}	_~	_42.56s	_43.02s	_{p=0.575 n=6}
_{Emit Time}	_{3.51s (± 2.75%)}	_{3.55s (± 2.16%)}	_~	_3.44s	_3.61s	_{p=0.630 n=6}
_{Total Time}	_{55.41s (± 0.69%)}	_{55.43s (± 0.61%)}	_~	_55.10s	_55.77s	_{p=1.000 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_263,074	_263,075	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_106,881	_106,882	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{441,364k (± 0.03%)}	_{441,342k (± 0.01%)}	_~	_441,253k	_441,414k	_{p=0.936 n=6}
_{Parse Time}	_{3.57s (± 1.07%)}	_{3.53s (± 0.77%)}	_~	_3.49s	_3.56s	_{p=0.064 n=6}
_{Bind Time}	_{1.31s (± 0.89%)}	_{1.31s (± 1.32%)}	_~	_1.28s	_1.33s	_{p=0.934 n=6}
_{Check Time}	_{18.98s (± 0.32%)}	_{19.00s (± 0.37%)}	_~	_18.90s	_19.08s	_{p=0.573 n=6}
_{Emit Time}	_{1.53s (± 1.15%)}	_{1.53s (± 1.15%)}	_~	_1.51s	_1.56s	_{p=0.868 n=6}
_{Total Time}	_{25.40s (± 0.42%)}	_{25.36s (± 0.27%)}	_~	_25.25s	_25.42s	_{p=0.470 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₇₀	₇₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_226,113	_226,113	_~	_~	_~	_{p=1.000 n=6}
_Types	_94,488	_94,488	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{371,741k (± 0.01%)}	_{371,823k (± 0.05%)}	_~	_371,669k	_372,216k	_{p=0.810 n=6}
_{Parse Time}	_{2.90s (± 1.24%)}	_{2.91s (± 0.67%)}	_~	_2.88s	_2.93s	_{p=1.000 n=6}
_{Bind Time}	_{1.58s (± 1.11%)}	_{1.61s (± 1.40%)}	_~	_1.59s	_1.64s	_{p=0.124 n=6}
_{Check Time}	_{16.52s (± 0.21%)}	_{16.48s (± 0.21%)}	_~	_16.43s	_16.52s	_{p=0.063 n=6}
_{Emit Time}	_0.00s	_{0.00s (±244.70%)}	_~	_0.00s	_0.01s	_{p=0.405 n=6}
_{Total Time}	_{21.01s (± 0.23%)}	_{21.00s (± 0.16%)}	_~	_20.96s	_21.05s	_{p=0.629 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_3,270,017	_3,270,019	_{+2 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_1,124,149	_1,124,152	_{+3 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{3,343,696k (± 0.00%)}	_{3,343,576k (± 0.01%)}	_~	_3,343,343k	_3,343,899k	_{p=0.298 n=6}
_{Parse Time}	_{18.01s (± 0.52%)}	_{18.17s (± 2.85%)}	_~	_17.89s	_19.22s	_{p=0.688 n=6}
_{Bind Time}	_{5.65s (± 2.13%)}	_{5.66s (± 2.11%)}	_~	_5.58s	_5.90s	_{p=0.628 n=6}
_{Check Time}	_{108.88s (± 1.59%)}	_{108.47s (± 0.76%)}	_~	_107.65s	_109.55s	_{p=1.000 n=6}
_{Emit Time}	_{34.16s (± 2.68%)}	_{34.88s (± 2.80%)}	_~	_33.59s	_35.98s	_{p=0.173 n=6}
_{Total Time}	_{166.70s (± 1.51%)}	_{167.18s (± 1.18%)}	_~	_164.92s	_169.77s	_{p=0.810 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_292,550	_292,550	_~	_~	_~	_{p=1.000 n=6}
_Types	_119,124	_119,124	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{446,170k (± 0.03%)}	_{446,072k (± 0.03%)}	_~	_445,956k	_446,266k	_{p=0.230 n=6}
_{Parse Time}	_{5.09s (± 1.28%)}	_{5.06s (± 0.69%)}	_~	_5.03s	_5.11s	_{p=0.414 n=6}
_{Bind Time}	_{2.24s (± 1.70%)}	_{2.22s (± 0.97%)}	_~	_2.20s	_2.25s	_{p=0.747 n=6}
_{Check Time}	_{23.36s (± 0.51%)}	_{23.34s (± 0.37%)}	_~	_23.21s	_23.43s	_{p=0.630 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{30.68s (± 0.44%)}	_{30.62s (± 0.36%)}	_~	_30.47s	_30.73s	_{p=0.470 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₅	₅	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_555,449	_555,449	_~	_~	_~	_{p=1.000 n=6}
_Types	_186,146	_186,146	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{494,626k (± 0.01%)}	_{494,549k (± 0.02%)}	_~	_494,322k	_494,630k	_{p=0.378 n=6}
_{Parse Time}	_{3.41s (± 0.67%)}	_{3.42s (± 0.86%)}	_~	_3.37s	_3.45s	_{p=0.224 n=6}
_{Bind Time}	_{1.20s (± 0.97%)}	_{1.21s (± 1.04%)}	_~	_1.20s	_1.23s	_{p=0.094 n=6}
_{Check Time}	_{19.67s (± 0.49%)}	_{19.75s (± 0.86%)}	_~	_19.57s	_20.04s	_{p=0.423 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{24.28s (± 0.49%)}	_{24.39s (± 0.74%)}	_~	_24.16s	_24.67s	_{p=0.230 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 · 2025-01-27T05:59:01Z

@jakebailey Here are the results of running the top 400 repos with tsc comparing main and refs/pull/61054/merge:

Everything looks good!

typescript-bot · 2026-03-24T21:21:15Z

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

Fixed instantiation expression type param leak in body-less arrows

ecc86b3

typescript-bot assigned weswigham Jan 26, 2025

typescript-bot added the For Milestone Bug PRs that fix a bug with a specific milestone label Jan 26, 2025

Andarist commented Jan 26, 2025

View reviewed changes

Andarist added 3 commits January 27, 2025 10:41

add extra test case

b0c4532

add yet another test

e105b89

reuse some of the existing logic

4069c6b

typescript-bot closed this Mar 24, 2026

github-project-automation Bot moved this from Not started to Done in PR Backlog Mar 24, 2026

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Fixed instantiation expression type param leak in body-less arrows#61054

Fixed instantiation expression type param leak in body-less arrows#61054
Andarist wants to merge 4 commits intomicrosoft:mainfrom
Andarist:fix/instantiation-expression-type-param-leak

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