IPromise.ts

export interface IThennable<Value, Reason> {
  then<
    FulfilledValue = never, FulfilledReason = never,
    RejectedValue = never, RejectedReason = never,
  >(
    onFulfilled?: (value: Value) => FulfilledValue | IThennable<FulfilledValue, FulfilledReason>,
    onRejected?: (reason: Reason) => RejectedValue | IThennable<RejectedValue, RejectedReason>,
  ): IThennable<FulfilledValue | RejectedValue, FulfilledReason | RejectedReason>;
}

export default interface IPromise<Value, Reason> extends IThennable<Value, Reason> {
  catch<RejectedValue = never, RejectedReason = never>(
    onRejected?: (reason: Reason) => RejectedValue | IThennable<RejectedValue, RejectedReason>,
  ): IThennable<RejectedValue, RejectedReason>;
}