🔎 Search Terms

type predicate mapped

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about type system behavior

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.2.2#code/IYIwzgLgTsDGEAJYBthjAgglEBLawUAngDwAqAfAgN4BQCCokM8SwAdgMoAWUu7AawDq+bgHsArhADCY9hACmADwgAKAG7BkEhQC4EEwezEB3dgEp9m7QoS4MZANy16jcAVZKiAL2+kAqhjKiuwAJhiGAsZmANoAuhSqrgxK+tQIMQDSduwIAgpEYgBmCIFx+oFZcQgAvgA0rpZYOPgwxCSBFM41LkweiChoGACyRNh4BO2UCMEKYRjjrYSk03QMfSyIXr4BQSpz4QZGpuzxickIqTQZ2fx5BcWlYOVPVbUNDE2Lk7tdtD1AA

💻 Code

abstract class Arbitrary<T> {
  abstract canShrinkWithoutContext(value: unknown): value is T;

  abstract xyzzy<Us extends unknown[]>(
    x: { [K in keyof Us]: Us[K] },
  ): Arbitrary<Us>;
}

abstract class MyArbitrary<T> extends Arbitrary<T> {
  abstract xyzzy<Us extends unknown[]>(
    x: { [K in keyof Us]: Us[K] },
  ): Arbitrary<Us>;
}

🙁 Actual behavior

The compiler reports an error in MyArbitrary unless canShrinkWithoutContext is removed or its return type is changed.

🙂 Expected behavior

The xyzzy method should be overridden in the derived class.

Additional information about the issue

No response