Type can't `keyof`

🔎 Search Terms

• keyof

🕗 Version & Regression Information

• This is a crash

⏯ Playground Link

No response

💻 Code

export type IsEqual<A, B> =
  (<T>() => T extends A ? 1 : 2) extends
  (<T>() => T extends B ? 1 : 2) ? true : false

export type IsNotEqual<A, B> =
  (<T>() => T extends A ? 1 : 2) extends
  (<T>() => T extends B ? 1 : 2) ? false : true

export interface Entries<X> {
  100000: [true extends (
    & IsNotEqual<X, ArrayConstructor>
    // Simplifying the problem here allows for the removal of the next line.
    & ([X] extends [ObjectConstructor] ? true : false)
  ) ? true : false, {
    check: (
      & IsNotEqual<X, ArrayConstructor>
      & ([X] extends [ObjectConstructor] ? true : false)
    ),
    x: X
  }]
  [key: number & {}]: [boolean, any]
}
type Mapping<
  X,
  E extends Entries<X> = Entries<X>
> = {
  [ K in keyof E
      as true extends (
        IsEqual<E[K & number][0], true>
      ) ? K : never
  ]: E[K & number][1]
}
type A0 = keyof Mapping<ObjectConstructor>
//   ^? type A0 = 100000
type A1 = ObjectConstructor extends infer T ? Mapping<T> : never
//   ^? type A1 = { 10000: { check: true; x: ObjectConstructor } }
type A2 = ObjectConstructor extends infer T ? keyof Mapping<T> : never
//   ^? type A2 = never
type A3 = [ObjectConstructor] extends [infer T] ? keyof Mapping<T> : never
//   ^? type A3 = never
type A4 = keyof (ObjectConstructor extends infer T ? Mapping<T> : never)
//   ^? type A4 = 11000

export {};
//   ^?

{
  "compilerOptions": {
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "declaration": true,
    "target": "ES2017",
    "jsx": "react",
    "module": "ESNext",
    "moduleResolution": "node"
  }
}

Playground Link: Provided

🙁 Actual behavior

In the case of A2, the type obtained through the operation cannot be used with keyof to obtain the Keys of the corresponding type.

🙂 Expected behavior

type A2 = 11000

Additional information about the issue

No response

Start with the provided TypeScript Playground reproduction and compare A2 with A0–A4, focusing on keyof evaluation for the conditional and mapped types shown. Done means the crash is resolved and A2 evaluates to 11000 without changing the expected behavior of the neighboring examples.