instantiation expression usage leading to an invalid d.ts file generation #60758

type SomePropertyKeys = ReadonlyArray<PropertyKey>
type At<A extends ReadonlyArray<unknown>, I extends number = number> = A[I]

export function mainKeyGuard<
  K extends readonly [PropertyKey, ...SomePropertyKeys],
>(
  keys: K,
): <T extends object>(
  value: T,
) => value is Extract<T, Record<At<K, 0>, unknown>> {
  return <T extends object>(
    value: T,
  ): value is Extract<T, Record<At<K, 0>, unknown>> => {
    return keys[0] in value
  }
}

type Foo = { foo1: string, foo2: string }
type Bar = { bar1: string, bar2: string }
type FooBar = Foo | Bar
const barKeys = ['bar1', 'bar2'] as const
export const isBar = mainKeyGuard(barKeys)<FooBar>

export declare const isBar: (value: FooBar) => value is Extract<T, Record<At<K, 0>, unknown>>;

export declare const isBar: (value: FooBar) => value is Bar;