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5.1 regression: constraints of generic tuple types are sometimes order-sensitive #54495
Description
Bug Report
🔎 Search Terms
- 5.1
- tuple
- array
- spread
Possibly related:
- Comparing a tuple input to a variadic tuple no longer narrows it #54048
- Tuple with optional element and exactOptionalPropertyTypes still returns undefined during iteration #54302
🕗 Version & Regression Information
- This changed between versions v5.0.4 and v5.1.3
⏯ Playground Link
I was unable to reproduce: if you could please steer me in the right direction I'm happy to dig more, but I'm a bit stuck on how to debug this
💻 Code
We have an issue using io-ts. If this is a bug with that library, I'll close this here, but I don't think it is.
The TypeScript compiler is complaining about a number of excerpts from the d.ts file, where the compiler doesn't seem to be making sense.
Here's an example error:
node_modules/io-ts/lib/index.d.ts:1151:24 - error TS2344: Type 'CS' does not satisfy the constraint '[Mixed, Mixed, Mixed[]]'.
Type '[Mixed, Mixed, ...Mixed[]]' is not assignable to type '[Mixed, Mixed, Mixed[]]'.
Target allows only 3 element(s) but source may have more.
1151 ) => TaggedUnionC<Tag, CS>
The code it's referring to is here:
export interface TaggedUnionC<Tag extends string, CS extends [Mixed, Mixed, ...Array<Mixed>]>
extends TaggedUnionType<Tag, CS, TypeOf<CS[number]>, OutputOf<CS[number]>, unknown> {}
export declare const taggedUnion: <Tag extends string, CS extends [Mixed, Mixed, ...Mixed[]]>(
tag: Tag,
codecs: CS,
name?: string
) => TaggedUnionC<Tag, CS>As you can see, the compiler seems to be collapsing the [Mixed, Mixed, ...Array<Mixed>] to [Mixed, Mixed, Mixed[]], which is incorrect. It then doesn't like CS extending [Mixed, Mixed, ...Mixed[]], which it considers incompatible with its incorrect collapsing.
Weirdly, if I tweak the d.ts file by hand, the error goes away:
- export interface TaggedUnionC<Tag extends string, CS extends [Mixed, Mixed, ...Array<Mixed>]>
+ export interface TaggedUnionC<Tag extends string, CS extends [Mixed, Mixed, ...Mixed[]]>🙁 Actual behavior
Compilation errors
🙂 Expected behavior
Successful compilation
Activity
RyanCavanaugh commentedon Jun 2, 2023
I'm not able to reproduce this error. Can you post a concrete example?
alecgibson commentedon Jun 2, 2023
Ryan Cavanaugh (@RyanCavanaugh) I tried to put together an MWE but I couldn't figure it out.
For some reason the error only happens with io-ts as a dependency of a dependency. The middle dependency compiles just fine with TS 5.1 and the issue only happens downstream with the transpiled JS and declaration files being used in 5.1.
Do you have any advice on how to get more information from TS, or a good guess at what might be the actual issue for me to narrow my search?
Andarist commentedon Jun 5, 2023
I'd recommend bisecting your situation by removing code from your dependencies, once you minimize this to a minimal repro you might want to just commit
node_modulesand share that as a repro case.alecgibson commentedon Jun 5, 2023
Okay Ryan Cavanaugh (@RyanCavanaugh) Mateusz Burzyński (@Andarist) I've got a minimal repro repo.
Turns out, nothing to do with our code, so either a TS bug, or a bug with another repo (still looks like TS to my uneducated eye, though).
The repro case — in the end — was laughably simple:
☝🏼 this fails to build with a bare-bones
tsconfig.jsonon TypeScript v5.1.3 with the compilation error I mentioned above.It builds fine on TypeScript v5.0.4.
alecgibson commentedon Jun 5, 2023
Please let me know if this is actually a bug with
mongodborio-ts, and I'll move there, but building a project that just depends on one of these libraries works just fine:import 'mongodb'; - import 'io-ts';or
- import 'mongodb'; import 'io-ts';both work
alecgibson commentedon Jun 5, 2023
Full error dump
Andarist commentedon Jun 5, 2023
This can be bisected to this PR #53672 , cc Anders Hejlsberg (@ahejlsberg)
That being said, this isn't quite a minimal repro case 😉
mongodbandio-tshave a lot of types and it might take a while for somebody to actually reduce this.Note that reordering those 2 imports also fixes the issue so it's likely a caching bug in the compiler. Things are cached for performance reasons and unfortunately, sometimes issues like this pop up and at times it's hard to fix them. Ideally, the order of declarations shouldn't matter but in practice, it sometimes might.
alecgibson commentedon Jun 5, 2023
Sorry I guess I meant minimal in terms of code I actually wrote 😅
Unfortunately I'm not sure I personally have time to unpick the internal type dependencies of these packages 😬
Mateusz Burzyński (@Andarist) I'm not really sure I understand what the actual issue is: do you have a suggestion for a more accurate issue title for this?
Andarist commentedon Jun 5, 2023
Maybe something like: "5.1 regression: constraints of generic tuple types are sometimes order-sensitive"
[-]5.1 Regression: Spread Array types inside tuple incorrectly collapsed[/-][+]5.1 regression: constraints of generic tuple types are sometimes order-sensitive[/+]alecgibson commentedon Jun 5, 2023
Okay I spotted something as I was skimming the MongoDB type declarations, and it looks like if you comment out this suspicious-looking type (and things that depend on it), everything compiles just fine.
I've pushed the result to the above repo as a new branch:
commented-depsIs this a TypeScript bug or a MongoDB bug?
alecgibson commentedon Jun 28, 2023
Mateusz Burzyński (@Andarist) Anders Hejlsberg (@ahejlsberg) this is still broken in
5.1.5. Should it be fixed?Andarist commentedon Jun 28, 2023
It seems that the fix was supposed to be cherry-picked into 5.1 but the automated job failed, see the comment here. cc Daniel Rosenwasser (@DanielRosenwasser) Jake Bailey (@jakebailey)
jakebailey commentedon Jun 28, 2023
I just sent #54814 to cherry-pick it by hand. Unfortunate; I totally read that notification in my email but I figured it was already handled...