21 lines
708 B
TypeScript
21 lines
708 B
TypeScript
interface IPromise<T> {
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then<U>(callback: (x: T) => IPromise<U>): IPromise<U>;
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}
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interface Promise<T> {
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then<U>(callback: (x: T) => Promise<U>): Promise<U>;
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}
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var x: IPromise<string>;
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var x: Promise<string>;
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interface IPromise2<T, V> {
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then<U, W>(callback: (x: T) => IPromise2<U, W>): IPromise2<W, U>;
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}
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interface Promise2<T, V> {
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then<U, W>(callback: (x: V) => Promise2<U, T>): Promise2<T, W>; // Uses V instead of T in callback's parameter
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}
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// Ok because T in this particular Promise2 is any, as are all the U and W references.
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// Also, the V of Promise2 happens to coincide with the T of IPromise2 (they are both string).
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var y: IPromise2<string, number>;
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var y: Promise2<any, string>; |