TS v4: Array#every throws on compilation for unions of arrays

[nicolas377]

🔎 Search Terms

.every, ReadonlyArray#every, array.every

🕗 Version & Regression Information

• This changed between versions 3.9.7 and 4.0.5

⏯ Playground Link

Playground link with relevant code

💻 Code

declare const someArray:
  | ["eslint:recommended", "plugin:import/recommended", "prettier"]
  | ["plugin:@typescript-eslint/recommended", "plugin:import/typescript"]
  | ["plugin:react/recommended"];

someArray.every((val: unknown) => typeof val === "string");

🙁 Actual behavior

TS(2349), because the signatures of the possible someArray.every calls conflict with each other.

🙂 Expected behavior

The someArray.every call should compile for all possible values of someArray.

Notes from the issue author

This is similar to #40157, but that issue uses a union of an array and 2D array.
Could be similar to #40217, but the error there was marked in a function call inside of the .every callback.
This issue is also reproducible using ReadonlyArray, see the playground for that.

[jcalz]

I'd say this is a duplicate of #44373

Of course it's also a duplicate of #40157, they are both unions of arrays with uncallable methods.

[RyanCavanaugh]

The someArray.every call should compile for all possible values of someArray.

Note that we very much intentionally do not things which are combinatorially explosive