Broken assignability and quick info due to erroneously deferring keyof T since #51621

@gabritto is already working on this.

Since Apr 30, 2026.

Note: This is a refiling of #61728 due to being closed due to being related to quick info display (see #62827).

### Version & Regression Information

This changed in PR https://github.com/microsoft/TypeScript/pull/51621

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

### Code:

Poor quick info:
```ts
type BasicConditional = keyof T extends any
? true
: false;

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

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

Broken assignability (found by @Andarist, see https://github.com/microsoft/TypeScript/issues/61728#issuecomment-2891710775)
```ts
type BasicConditional = keyof T extends infer R ? R : never;

type Config = { rejectClose: true };

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

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

const ok: BasicConditional = "rejectClose"; // No error
```

### Actual behavior

`RejectClose`'s quick info is `keyof Config extends any ? true : false` which is un-simplified and rather ugly. In addition in the second snippet `const test: Test["rejectClose"] = "rejectClose";` fails.

### Expected behavior

The quick info should look nice and `const test: Test["rejectClose"] = "rejectClose";` should succeed.

See https://github.com/microsoft/TypeScript/pull/61999 for a TS-JS based fix.