Reduce intersections of constrained type variables and primitive types by ahejlsberg · Pull Request #56515 · microsoft/TypeScript

Anders Hejlsberg (ahejlsberg) · 2023-11-22T22:36:21Z

With this PR we reduce intersections of constrained type variables and primitive types as follows:

An intersection T & P or P & T, where T's constraint is a subtype of P, is reduced to just T. For example, given T extends "a" | "b", the intersection T & string is reduced to just T.
An intersection T & P or P & T, where no constituent of T's constraint is a subtype of P, and P is not a subtype of T's constraint, is reduced to never. For example, given T extends "a" | "b", the intersection T & number is reduced to never.
In a union containing intersections of a type variable and primitive types that fully cover the constraint of that type variable, the intersections are replaced with just the type variable. For example, given T extends "a" | "b", the union type T & "a" | T & "b" is reduced to just T.

Anders Hejlsberg (ahejlsberg) · 2023-11-22T22:37:33Z

TypeScript Bot (@typescript-bot) test top100
TypeScript Bot (@typescript-bot) user test this
TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test this faster

TypeScript Bot (typescript-bot) · 2023-11-22T22:37:36Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the tsc-only perf test suite on this PR at 5b6f969. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-11-22T22:37:36Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the parallelized Definitely Typed test suite on this PR at 5b6f969. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-11-22T22:37:36Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the diff-based user code test suite on this PR at 5b6f969. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-11-22T22:37:36Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the diff-based top-repos suite on this PR at 5b6f969. You can monitor the build here.

Update: The results are in!

Jake Bailey (jakebailey) · 2023-11-22T22:42:23Z


 value; // T & {}
->value : T & ({} | null)
+>value : never


This seems funky; T could be 42 here but it's thinking that comparison is impossible and made never.

It's actually existing behavior that is being revealed by the reduction of T & ({} | null) to just T. We have logic somewhere in the comparable relation that considers a naked type parameter constrained to {} to be something that always represents an object.

TypeScript Bot (typescript-bot) · 2023-11-22T22:49:31Z

Anders Hejlsberg (@ahejlsberg)
The results of the perf run you requested are in!

Here they are:

Compiler

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Angular - node (v18.15.0, x64)}
_{Memory used}	_{295,193k (± 0.01%)}	_{295,206k (± 0.01%)}	_~	_295,188k	_295,236k	_{p=0.229 n=6}
_{Parse Time}	_{2.64s (± 0.29%)}	_{2.65s (± 0.32%)}	_~	_2.64s	_2.66s	_{p=0.209 n=6}
_{Bind Time}	_{0.83s (± 0.99%)}	_{0.82s (± 0.50%)}	_~	_0.82s	_0.83s	_{p=0.248 n=6}
_{Check Time}	_{8.04s (± 0.21%)}	_{8.05s (± 0.31%)}	_~	_8.00s	_8.07s	_{p=0.329 n=6}
_{Emit Time}	_{7.07s (± 0.39%)}	_{7.07s (± 0.42%)}	_~	_7.04s	_7.11s	_{p=0.743 n=6}
_{Total Time}	_{18.57s (± 0.18%)}	_{18.59s (± 0.11%)}	_~	_18.56s	_18.62s	_{p=0.291 n=6}
_{Compiler-Unions - node (v18.15.0, x64)}
_{Memory used}	_{192,514k (± 1.21%)}	_{192,651k (± 1.58%)}	_~	_190,638k	_196,700k	_{p=0.936 n=6}
_{Parse Time}	_{1.35s (± 1.05%)}	_{1.35s (± 1.09%)}	_~	_1.34s	_1.38s	_{p=1.000 n=6}
_{Bind Time}	_{0.72s (± 0.00%)}	_{0.72s (± 0.00%)}	_~	_0.72s	_0.72s	_{p=1.000 n=6}
_{Check Time}	_{9.21s (± 0.42%)}	_{9.16s (± 0.69%)}	_~	_9.10s	_9.25s	_{p=0.418 n=6}
_{Emit Time}	_{2.61s (± 0.39%)}	_{2.61s (± 0.31%)}	_~	_2.60s	_2.62s	_{p=0.932 n=6}
_{Total Time}	_{13.88s (± 0.24%)}	_{13.85s (± 0.46%)}	_~	_13.77s	_13.93s	_{p=0.470 n=6}
_{Monaco - node (v18.15.0, x64)}
_{Memory used}	_{347,373k (± 0.01%)}	_{347,372k (± 0.00%)}	_~	_347,350k	_347,398k	_{p=0.575 n=6}
_{Parse Time}	_{2.46s (± 0.42%)}	_{2.46s (± 0.40%)}	_~	_2.45s	_2.47s	_{p=0.933 n=6}
_{Bind Time}	_{0.93s (± 0.56%)}	_{0.92s (± 0.56%)}	_~	_0.92s	_0.93s	_{p=0.311 n=6}
_{Check Time}	_{6.91s (± 0.56%)}	_{6.91s (± 0.51%)}	_~	_6.87s	_6.96s	_{p=1.000 n=6}
_{Emit Time}	_{4.05s (± 0.19%)}	_{4.05s (± 0.20%)}	_~	_4.04s	_4.06s	_{p=0.729 n=6}
_{Total Time}	_{14.35s (± 0.26%)}	_{14.35s (± 0.23%)}	_~	_14.30s	_14.40s	_{p=1.000 n=6}
_{TFS - node (v18.15.0, x64)}
_{Memory used}	_{302,633k (± 0.00%)}	_{302,638k (± 0.01%)}	_~	_302,618k	_302,662k	_{p=0.688 n=6}
_{Parse Time}	_{1.99s (± 1.66%)}	_{2.00s (± 0.86%)}	_~	_1.98s	_2.03s	_{p=0.686 n=6}
_{Bind Time}	_{1.00s (± 0.75%)}	_{1.01s (± 1.20%)}	_~	_0.99s	_1.02s	_{p=0.240 n=6}
_{Check Time}	_{6.26s (± 0.46%)}	_{6.28s (± 0.41%)}	_~	_6.25s	_6.32s	_{p=0.124 n=6}
_{Emit Time}	_{3.59s (± 0.48%)}	_{3.58s (± 0.42%)}	_~	_3.56s	_3.60s	_{p=0.279 n=6}
_{Total Time}	_{12.84s (± 0.39%)}	_{12.87s (± 0.26%)}	_~	_12.82s	_12.91s	_{p=0.295 n=6}
_{material-ui - node (v18.15.0, x64)}
_{Memory used}	_{470,630k (± 0.02%)}	_{470,642k (± 0.01%)}	_~	_470,600k	_470,681k	_{p=0.378 n=6}
_{Parse Time}	_{2.57s (± 0.63%)}	_{2.57s (± 0.79%)}	_~	_2.55s	_2.60s	_{p=0.867 n=6}
_{Bind Time}	_{0.99s (± 1.22%)}	_{0.98s (± 0.56%)}	_~	_0.98s	_0.99s	_{p=0.235 n=6}
_{Check Time}	_{16.74s (± 0.49%)}	_{16.76s (± 0.28%)}	_~	_16.70s	_16.83s	_{p=0.375 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{20.30s (± 0.50%)}	_{20.32s (± 0.27%)}	_~	_20.25s	_20.41s	_{p=0.372 n=6}
_{xstate - node (v18.15.0, x64)}
_{Memory used}	_{511,983k (± 0.01%)}	_{511,891k (± 0.01%)}	_{-91k (- 0.02%)}	_511,862k	_511,941k	_{p=0.008 n=6}
_{Parse Time}	_{3.27s (± 0.23%)}	_{3.27s (± 0.36%)}	_~	_3.25s	_3.28s	_{p=0.796 n=6}
_{Bind Time}	_{1.54s (± 0.00%)}	_{1.55s (± 0.26%)}	_{+0.01s (+ 0.54%)}	_1.54s	_1.55s	_{p=0.007 n=6}
_{Check Time}	_{2.79s (± 0.67%)}	_{2.77s (± 0.95%)}	_~	_2.74s	_2.80s	_{p=0.252 n=6}
_{Emit Time}	_{0.08s (± 0.00%)}	_{0.08s (± 4.99%)}	_~	_0.08s	_0.09s	_{p=0.405 n=6}
_{Total Time}	_{7.68s (± 0.27%)}	_{7.67s (± 0.35%)}	_~	_7.64s	_7.70s	_{p=0.466 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

Angular - node (v18.15.0, x64)
Compiler-Unions - node (v18.15.0, x64)
Monaco - node (v18.15.0, x64)
TFS - node (v18.15.0, x64)
material-ui - node (v18.15.0, x64)
xstate - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

TypeScript Bot (typescript-bot) · 2023-11-22T22:56:43Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the user test suite comparing main and refs/pull/56515/merge:

There were infrastructure failures potentially unrelated to your change:

2 instances of "Package install failed"

Otherwise...

Something interesting changed - please have a look.

Details

puppeteer

packages/browsers/test/src/tsconfig.json

[MISSING] error TS2307: Cannot find module '@pptr/testserver' or its corresponding type declarations.
- packages/browsers/test/src/utils.ts#L23 in packages/browsers/test/src/tsconfig.json

TypeScript Bot (typescript-bot) · 2023-11-22T23:29:25Z

Hey Anders Hejlsberg (@ahejlsberg), the results of running the DT tests are ready.
There were interesting changes:

Branch only errors:

Package: enzyme
Error:

Error: /home/vsts/work/1/DefinitelyTyped/types/enzyme/enzyme-tests.tsx:106:9
ERROR: 106:9 expect TypeScript@local compile error: Unused '@ts-expect-error' directive.
at testTypesVersion (/home/vsts/work/1/DefinitelyTyped/node_modules/.pnpm/@definitelytyped+dtslint@0.0.196_typescript@5.4.0-dev.20231122/node_modules/@definitelytyped/dtslint/dist/index.js:176:15)
at async runTests (/home/vsts/work/1/DefinitelyTyped/node_modules/.pnpm/@definitelytyped+dtslint@0.0.196_typescript@5.4.0-dev.20231122/node_modules/@definitelytyped/dtslint/dist/index.js:135:9)

You can check the log here.

TypeScript Bot (typescript-bot) · 2023-11-22T23:45:31Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the top-repos suite comparing main and refs/pull/56515/merge:

Everything looks good!

Anders Hejlsberg (ahejlsberg) · 2023-11-28T13:58:01Z

The new error in the Definitely Typed enzyme package is related to a type of the form

typeKeys<P>={[KinkeyofP]: K}[keyofP];

In the enzyme package there is an application of NonNullable<Keys>, which corresponds to Keys & {}. The constraint of Keys is string | number | symbol (i.e. the type of any valid property key). With the new functionality in this PR, the intersection Keys & {} gets reduced to just Keys because the constraint indicates the type can't be null or undefined.

However, upon instantiation with a type that contains optional properties, the resulting type will actually include undefined. For example

typeFoo={a?: string;b: number;}typeFooKeys=Keys<Foo>;// "a" | "b" | undefined

Since Keys is homomorphic, modifiers (such as optionality) are copied from the properties of the source type, and that ends up adding undefined to the optional properties. This behavior is as expected.

The issue here really is that the constraint of Keys should include undefined--because the type might be applied to something with optional properties. I tried implementing that, but it causes a whole slew of new errors that technically are correct, but break existing code. So, I think the cure is worse than the disease there.

Generally, types like Keys should be written to exclude optionality from the properties:

typeKeys<P>={[KinkeyofP]-?: K}[keyofP];

With this change there are no new errors in enzyme.

Gabriela Araujo Britto (gabritto) · 2023-11-28T19:42:51Z

TypeScript Bot (@typescript-bot) pack this

TypeScript Bot (typescript-bot) · 2023-11-28T19:42:56Z

Heya Gabriela Araujo Britto (@gabritto), I've started to run the tarball bundle task on this PR at 5b6f969. You can monitor the build here.

TypeScript Bot (typescript-bot) · 2023-11-28T19:44:52Z

Hey Gabriela Araujo Britto (@gabritto), 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/158848/artifacts?artifactName=tgz&fileId=EB88B1ED0A330275E743D467B388586ABE3607D9A44B45B5C76D42D6978682EF02&fileName=/typescript-5.4.0-insiders.20231128.tgz"
}
}

and then running npm install.

There is also a playground for this build and an npm module you can use via "typescript": "npm:@typescript-deploys/pr-build@5.4.0-pr-56515-12".;

Wesley Wigham (weswigham)

I had to include a similar change in the not types PR to get them to work decently - I think this is a pretty good simplification to perform on union (and intersection) construction (since making the type smaller is basically always good).

The one thing I worry a bit about though, if when you reduce T & U to just T, you remove the intersection entirely, which means you remove the type an alias could have been pinned to, which could be an observable change. Hopefully it doesn't matter in practice - I'm hoping there's no type Int<T extends number> = T & number; style types too prevalent in the wild.

…S intersection constrained types More details: microsoft/TypeScript#56515

Anders Hejlsberg (ahejlsberg) added 3 commits November 22, 2023 14:01

Reduce intersections of constrained type variables and primitive types
16c1d9d

Accept new baselines
4bf6ae7

Add tests
5b6f969

TypeScript Bot (typescript-bot) assigned Anders Hejlsberg (ahejlsberg)Nov 22, 2023

TypeScript Bot (typescript-bot) added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Nov 22, 2023

Jake Bailey (jakebailey) reviewed Nov 22, 2023
View reviewed changes

Wesley Wigham (weswigham) approved these changes Nov 29, 2023
View reviewed changes

Anders Hejlsberg (ahejlsberg) merged commit 3258d75 into mainNov 30, 2023

Anders Hejlsberg (ahejlsberg) deleted the typeVariableIntersections branch November 30, 2023 15:04

Sebastian "Sebbie" Silbermann (eps1lon) mentioned this pull request Dec 2, 2023
[enzyme] Fix TypeScript 5.4-dev compat DefinitelyTyped/DefinitelyTyped#67582
Merged

This was referenced Dec 2, 2023
TypeScript 5.4: NonNullable does not always exclude undefined#56644
Closed
Crash on 5.4.0-dev.20231206 #56688
Closed

Jake Bailey (jakebailey) mentioned this pull request Dec 7, 2023
[react/v16] Hack to fix 'too complex' message in editor / new ExpectType linter DefinitelyTyped/DefinitelyTyped#67819
Merged

Ryan Cavanaugh (RyanCavanaugh) mentioned this pull request Jan 23, 2024
[NewErrors] 5.4.0-dev.20240121 vs 5.3.3 #57117
Closed

Daniel Rosenwasser (DanielRosenwasser) mentioned this pull request Jan 24, 2024
Move Equals constraint into an intersection type. reduxjs/react-redux#2123
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Mateusz Burzyński (Andarist) mentioned this pull request Jan 29, 2024
[5.4 regression] Conditional type changes behavior with 5.4-beta #57221
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This was referenced Jan 30, 2024
Design Meeting Notes, 1/24/2024 #57241
Closed
Design Meeting Notes, 1/26/2024 #57242
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Ryan Cavanaugh (RyanCavanaugh) mentioned this pull request Mar 12, 2024
Regression in distributing on conditional types with T extends T after updating to 5.4 #57736
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Nazar Hussain (nazarhussain) mentioned this pull request Mar 15, 2024
deps: upgrade typescript to 5.4 ChainSafe/lodestar#6552
Merged

Daniele Iasella (overbit) added a commit to amplication/amplication that referenced this pull request Mar 26, 2024
fix(dsg): type issue in base service findmany method to support new T…
ee202d7
…S intersection constrained types More details: microsoft/TypeScript#56515

Daniele Iasella (overbit) mentioned this pull request Mar 26, 2024
fix(dsg): type issues related to ts v5.4+ changes amplication/amplication#8248
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2 tasks

Ryan Cavanaugh (RyanCavanaugh) mentioned this pull request Apr 24, 2024
Type alias circularly references itself (5.4 regression) #58302
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Mateusz Burzyński (Andarist) mentioned this pull request Sep 17, 2024
Exclude undefined from constraints of mapped type type parameters #59995
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Mateusz Burzyński (Andarist) mentioned this pull request Sep 28, 2024
Missing reduction step in a union of intersections with bounded type parameter #48718
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puppeteer

packages/browsers/test/src/tsconfig.json

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