Use strict subtype relation in `getCommonSupertype` #61903

ahejlsberg · 2025-06-19T15:10:09Z

Experiment to see effects of using strict subtype relation in getCommonSupertype.

Copilot

Pull Request Overview

This PR experiments with using a strict subtype relation in the computation of a common supertype.

Switched from isTypeSubtypeOf to isTypeStrictSubtypeOf in reduceLeft for type comparison.
Aims to leverage structural subtype relations for improved type accuracy.

Comments suppressed due to low confidence (1)

ahejlsberg · 2025-06-19T15:10:31Z

@typescript-bot test it

typescript-bot · 2025-06-19T15:10:36Z

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 · 2025-06-19T15:32:43Z

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

Everything looks the same!

You can check the log here.

typescript-bot · 2025-06-19T15:36:44Z

@ahejlsberg Here are the results of running the user tests with tsc comparing main and refs/pull/61903/merge:

Something interesting changed - please have a look.

Details

fp-ts

tsconfig.json

[NEW] error TS2345: Argument of type 'Option<(Map<{ id: number; }, { value: number; }> | { value: number; })[]>' is not assignable to parameter of type 'Option<[Value, Map<Key, Value>]>'.
- test/Map.ts#L460
- test/Map.ts#L461
[NEW] error TS2345: Argument of type 'Option<(number | { id: string; })[]>' is not assignable to parameter of type 'Option<[User, number]>'.
- test/Map.ts#L476
- test/Map.ts#L478
[NEW] error TS2345: Argument of type 'Option<{ x: number; }[]>' is not assignable to parameter of type 'Option<NonEmptyArray<{ readonly x: number; }>>'.

tsconfig.eslint.json

[NEW] error TS2345: Argument of type 'Option<(Map<{ id: number; }, { value: number; }> | { value: number; })[]>' is not assignable to parameter of type 'Option<[Value, Map<Key, Value>]>'.
- test/Map.ts#L460
- test/Map.ts#L461
[NEW] error TS2345: Argument of type 'Option<(number | { id: string; })[]>' is not assignable to parameter of type 'Option<[User, number]>'.
- test/Map.ts#L476
- test/Map.ts#L478
[NEW] error TS2345: Argument of type 'Option<{ x: number; }[]>' is not assignable to parameter of type 'Option<NonEmptyArray<{ readonly x: number; }>>'.

typescript-bot · 2025-06-19T15:55:09Z

@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 - 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}	_{194,139k (± 0.99%)}	_{194,125k (± 0.96%)}	_~	_192,894k	_196,572k	_{p=0.688 n=6}
_{Parse Time}	_1.29s	_{1.30s (± 0.75%)}	_{+0.01s (+ 0.90%)}	_1.29s	_1.31s	_{p=0.027 n=6}
_{Bind Time}	_0.73s	_0.73s	_~	_~	_~	_{p=1.000 n=6}
_{Check Time}	_{9.67s (± 0.25%)}	_{9.68s (± 0.32%)}	_~	_9.64s	_9.72s	_{p=0.687 n=6}
_{Emit Time}	_{2.75s (± 0.56%)}	_{2.74s (± 0.83%)}	_~	_2.71s	_2.77s	_{p=0.511 n=6}
_{Total Time}	_{14.45s (± 0.23%)}	_{14.45s (± 0.23%)}	_~	_14.42s	_14.51s	_{p=1.000 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₅₆	₅₆	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_948,750	_948,753	_{+3 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_410,846	_410,846	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{1,224,587k (± 0.00%)}	_{1,224,623k (± 0.00%)}	_~	_1,224,593k	_1,224,698k	_{p=0.054 n=6}
_{Parse Time}	_{6.60s (± 0.94%)}	_{6.60s (± 0.75%)}	_~	_6.53s	_6.65s	_{p=0.872 n=6}
_{Bind Time}	_{1.89s (± 0.80%)}	_{1.88s (± 0.44%)}	_~	_1.87s	_1.89s	_{p=0.607 n=6}
_{Check Time}	_{31.74s (± 0.29%)}	_{31.91s (± 0.15%)}	_{+0.17s (+ 0.55%)}	_31.84s	_31.99s	_{p=0.005 n=6}
_{Emit Time}	_{14.85s (± 0.42%)}	_{14.93s (± 0.43%)}	_~	_14.85s	_15.00s	_{p=0.054 n=6}
_{Total Time}	_{55.07s (± 0.20%)}	_{55.33s (± 0.21%)}	_{+0.25s (+ 0.46%)}	_55.14s	_55.47s	_{p=0.013 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,561,658	_2,561,642	_{-16 (- 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_892,631	_892,620	_{-11 (- 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,836,562k (± 0.00%)}	_{2,836,651k (± 0.00%)}	_{+89k (+ 0.00%)}	_2,836,555k	_2,836,698k	_{p=0.031 n=6}
_{Parse Time}	_{9.20s (± 0.43%)}	_{9.20s (± 0.28%)}	_~	_9.16s	_9.22s	_{p=0.809 n=6}
_{Bind Time}	_{2.31s (± 0.24%)}	_{2.30s (± 0.70%)}	_~	_2.27s	_2.31s	_{p=0.663 n=6}
_{Check Time}	_{83.49s (± 0.29%)}	_{83.76s (± 0.47%)}	_~	_83.44s	_84.47s	_{p=0.467 n=6}
_{Emit Time}	_{0.30s (± 1.74%)}	_{0.30s (± 1.35%)}	_~	_0.30s	_0.31s	_{p=0.114 n=6}
_{Total Time}	_{95.29s (± 0.25%)}	_{95.56s (± 0.43%)}	_~	_95.19s	_96.27s	_{p=0.575 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,227,126	_1,227,031	_{-95 (- 0.01%)}	_~	_~	_{p=0.001 n=6}
_Types	_267,408	_267,400	_{-8 (- 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,973,403k (±10.02%)}	_{2,607,151k (±14.50%)}	_~	_2,361,777k	_3,096,441k	_{p=0.230 n=6}
_{Parse Time}	_{6.66s (± 0.90%)}	_{6.60s (± 1.61%)}	_~	_6.53s	_6.77s	_{p=0.378 n=6}
_{Bind Time}	_{2.20s (± 1.02%)}	_{2.19s (± 1.13%)}	_~	_2.16s	_2.22s	_{p=0.809 n=6}
_{Check Time}	_{42.79s (± 0.47%)}	_{42.89s (± 0.42%)}	_~	_42.67s	_43.12s	_{p=0.521 n=6}
_{Emit Time}	_{3.48s (± 1.30%)}	_{3.56s (± 3.87%)}	_~	_3.34s	_3.73s	_{p=0.230 n=6}
_{Total Time}	_{55.13s (± 0.35%)}	_{55.24s (± 0.39%)}	_~	_54.94s	_55.54s	_{p=0.471 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,227,126	_1,227,031	_{-95 (- 0.01%)}	_~	_~	_{p=0.001 n=6}
_Types	_267,408	_267,400	_{-8 (- 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,611,033k (±11.64%)}	_{2,428,786k (± 0.01%)}	_{🟩-182,247k (- 6.98%)}	_2,428,455k	_2,429,093k	_{p=0.013 n=6}
_{Parse Time}	_{5.45s (± 0.92%)}	_{5.40s (± 0.77%)}	_~	_5.36s	_5.46s	_{p=0.077 n=6}
_{Bind Time}	_{1.82s (± 1.62%)}	_{1.83s (± 1.57%)}	_~	_1.79s	_1.86s	_{p=0.416 n=6}
_{Check Time}	_{35.20s (± 0.69%)}	_{35.08s (± 0.13%)}	_~	_35.00s	_35.13s	_{p=0.298 n=6}
_{Emit Time}	_{3.04s (± 1.96%)}	_{3.04s (± 1.33%)}	_~	_2.99s	_3.10s	_{p=0.810 n=6}
_{Total Time}	_{45.50s (± 0.57%)}	_{45.35s (± 0.20%)}	_~	_45.25s	_45.48s	_{p=0.230 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_262,474	_262,514	_{+40 (+ 0.02%)}	_~	_~	_{p=0.001 n=6}
_Types	_107,135	_107,137	_{+2 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{441,696k (± 0.01%)}	_{441,722k (± 0.01%)}	_~	_441,695k	_441,764k	_{p=0.173 n=6}
_{Parse Time}	_{3.52s (± 1.20%)}	_{3.52s (± 0.76%)}	_~	_3.49s	_3.56s	_{p=1.000 n=6}
_{Bind Time}	_{1.33s (± 0.78%)}	_{1.32s (± 0.92%)}	_~	_1.30s	_1.33s	_{p=0.180 n=6}
_{Check Time}	_{18.87s (± 0.19%)}	_{18.89s (± 0.69%)}	_~	_18.73s	_19.11s	_{p=1.000 n=6}
_{Emit Time}	_{1.52s (± 1.13%)}	_{1.52s (± 1.93%)}	_~	_1.47s	_1.55s	_{p=0.462 n=6}
_{Total Time}	_{25.24s (± 0.29%)}	_{25.26s (± 0.55%)}	_~	_25.12s	_25.49s	_{p=1.000 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₇₁	₇₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_225,327	_225,367	_{+40 (+ 0.02%)}	_~	_~	_{p=0.001 n=6}
_Types	_94,288	_94,290	_{+2 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{371,114k (± 0.03%)}	_{371,102k (± 0.01%)}	_~	_371,057k	_371,140k	_{p=0.630 n=6}
_{Parse Time}	_{2.88s (± 0.97%)}	_{2.89s (± 0.78%)}	_~	_2.87s	_2.93s	_{p=0.627 n=6}
_{Bind Time}	_{1.58s (± 1.36%)}	_{1.58s (± 0.74%)}	_~	_1.56s	_1.59s	_{p=1.000 n=6}
_{Check Time}	_{16.27s (± 0.16%)}	_{16.29s (± 0.56%)}	_~	_16.18s	_16.42s	_{p=0.809 n=6}
_{Emit Time}	_{0.00s (±244.70%)}	_0.00s	_~	_~	_~	_{p=0.405 n=6}
_{Total Time}	_{20.74s (± 0.26%)}	_{20.76s (± 0.50%)}	_~	_20.64s	_20.92s	_{p=0.872 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₃₃	₃₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_3,475,334	_3,475,213	_{-121 (- 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_1,168,527	_1,168,445	_{-82 (- 0.01%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{3,521,660k (± 0.01%)}	_{3,521,455k (± 0.01%)}	_~	_3,520,939k	_3,521,647k	_{p=0.230 n=6}
_{Parse Time}	_{15.09s (± 0.36%)}	_{14.98s (± 0.49%)}	_{-0.10s (- 0.70%)}	_14.89s	_15.11s	_{p=0.045 n=6}
_{Bind Time}	_{4.85s (± 0.43%)}	_{4.84s (± 0.65%)}	_~	_4.79s	_4.88s	_{p=1.000 n=6}
_{Check Time}	_{97.05s (± 3.21%)}	_{94.04s (± 1.46%)}	_~	_93.14s	_96.81s	_{p=0.128 n=6}
_{Emit Time}	_{29.86s (± 2.87%)}	_{30.23s (± 7.57%)}	_~	_29.12s	_34.90s	_{p=0.575 n=6}
_{Total Time}	_{146.84s (± 2.54%)}	_{144.10s (± 2.54%)}	_~	_142.11s	_151.55s	_{p=0.230 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_320,000	_320,000	_~	_~	_~	_{p=1.000 n=6}
_Types	_140,356	_140,356	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{474,193k (± 0.03%)}	_{474,175k (± 0.02%)}	_~	_474,034k	_474,380k	_{p=0.936 n=6}
_{Parse Time}	_{4.31s (± 1.04%)}	_{4.33s (± 1.04%)}	_~	_4.26s	_4.40s	_{p=0.747 n=6}
_{Bind Time}	_{1.77s (± 1.78%)}	_{1.77s (± 0.83%)}	_~	_1.75s	_1.79s	_{p=0.627 n=6}
_{Check Time}	_{20.70s (± 0.54%)}	_{20.72s (± 0.35%)}	_~	_20.63s	_20.83s	_{p=0.873 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{26.78s (± 0.61%)}	_{26.83s (± 0.26%)}	_~	_26.74s	_26.93s	_{p=0.689 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₃₀	₃₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_667,036	_667,036	_~	_~	_~	_{p=1.000 n=6}
_Types	_198,508	_198,508	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{569,721k (± 0.00%)}	_{569,687k (± 0.01%)}	_~	_569,633k	_569,734k	_{p=0.199 n=6}
_{Parse Time}	_{5.50s (± 0.48%)}	_{5.55s (± 0.46%)}	_{+0.04s (+ 0.79%)}	_5.51s	_5.58s	_{p=0.028 n=6}
_{Bind Time}	_{1.66s (± 1.18%)}	_{1.66s (± 0.83%)}	_~	_1.63s	_1.67s	_{p=0.625 n=6}
_{Check Time}	_{25.34s (± 0.65%)}	_{25.33s (± 0.45%)}	_~	_25.19s	_25.50s	_{p=0.810 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{32.52s (± 0.51%)}	_{32.54s (± 0.35%)}	_~	_32.40s	_32.71s	_{p=1.000 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 · 2025-06-19T16:55:48Z

@ahejlsberg Here are the results of running the top 400 repos with tsc comparing main and refs/pull/61903/merge:

Something interesting changed - please have a look.

Details

glideapps/quicktype

7 of 9 projects failed to build with the old tsc and were ignored

packages/quicktype-core/tsconfig.json

error TS2339: Property '$ref' does not exist on type '{}'.
- packages/quicktype-core/src/language/JSONSchema/JSONSchemaRenderer.ts#L110

outline/outline

tsconfig.json

error TS2345: Argument of type '(Group | Suggestion)[]' is not assignable to parameter of type 'Many<User>'.
- app/components/Sharing/components/Suggestions.tsx#L188

vuetifyjs/vuetify

3 of 7 projects failed to build with the old tsc and were ignored

packages/vuetify/tsconfig.json

error TS2739: Type 'Ref<any, any>' is missing the following properties from type 'ComputedRef<Set<unknown> | null>': effect, [ComputedRefSymbol]
- packages/vuetify/src/labs/VTreeview/VTreeviewItem.tsx#L38

packages/vuetify/tsconfig.dist.json

error TS2739: Type 'Ref<any, any>' is missing the following properties from type 'ComputedRef<Set<unknown> | null>': effect, [ComputedRefSymbol]
- packages/vuetify/src/labs/VTreeview/VTreeviewItem.tsx#L38

Use strict subtype relation in getCommonSupertype

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Copilot AI review requested due to automatic review settings June 19, 2025 15:10

github-project-automation bot added this to PR Backlog Jun 19, 2025

github-project-automation bot moved this to Not started in PR Backlog Jun 19, 2025

typescript-bot assigned ahejlsberg Jun 19, 2025

typescript-bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Jun 19, 2025

Copilot AI reviewed Jun 19, 2025

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ahejlsberg mentioned this pull request Jun 19, 2025

Type inference broken with angular inject function + @ngrx/store microsoft/typescript-go#1222

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Use strict subtype relation in `getCommonSupertype` #61903

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Use strict subtype relation in `getCommonSupertype` #61903

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