Poor quick info due to erroneously deferring `keyof T` since #51621

[LukeAbby]

🔎 Search Terms

quick info, hover hint, deferred keyof

🕗 Version & Regression Information

• This changed in PR Fixed substition types for non-generic indexed accesses #51621

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.8.3#code/C4TwDgpgBAQghgZwJYGMDCB7AdgEycJbOAGwB4AVAPigF4oBrCEDAMynKggA9gJcEocLCABQUKAH4owAE4BXCGKgAuKCxIIIAbhEjQkKJiwskAc1pQA3lBkQAVhBTA0xDJtWyFUAL4790cggEYFolIxNzbl5+K28lcSlLePEU2wcnFzcIVXhkdGw8AiIycLNKHRSUuMrVLAgANwgZHT1waAAle0dnV00LQOCAbQAiNO7MzWGAXR0AelmUgD0pRmY2UsiePhwBIRBJaXloVXViTSA

💻 Code

type BasicConditional<T> = keyof T extends any
  ? true
  : false;

type Config = { rejectClose: true };
type Test =
  Config extends {}
    ? {
        rejectClose: BasicConditional<Config>;
      }
    : never;

type RejectClose = Test["rejectClose"];
//   ^? keyof Config extends any ? true : false

🙁 Actual behavior

RejectClose's quick info is keyof Config extends any ? true : false which is un-simplified and rather ugly.

🙂 Expected behavior

RejectClose should be simplified to just true in this case.

Additional information about the issue

No response

[Andarist]

I'm working on the fix 🫡

[LukeAbby]

Mateusz Burzyński (@Andarist) found that this is apparently more severe than I had expected:

type BasicConditional<T> = keyof T extends infer R ? R : never;

type Config = { rejectClose: true };

type Test = Config extends {}
  ? {
      rejectClose: BasicConditional<Config>;
    }
  : never;

const test: Test["rejectClose"] = "rejectClose";
//    ^ Type 'string' is not assignable to type 'BasicConditional<Config>'.

const ok: BasicConditional<Config> = "rejectClose"; // No error

It appears that this can actually break assignability!

[RyanCavanaugh]

Closing language service bugs related to the 6.0 implementation. For more information, see #62827