cd30534327
* Support recursive conditional types * Accept new API baselines * Accept new baselines * Simplify recursive type tracking in type inference * Accept new baselines * Add tests * Accept new baselines * Revise recursion tracking in type inference * Revise tests * Accept new baselines * Add more tests * Accept new baselines
122 lines
3.6 KiB
TypeScript
122 lines
3.6 KiB
TypeScript
// @strict: true
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// @declaration: true
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// @target: esnext
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// Awaiting promises
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type Awaited<T> =
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T extends null | undefined ? T :
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T extends PromiseLike<infer U> ? Awaited<U> :
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T;
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type MyPromise<T> = {
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then<U>(f: ((value: T) => U | PromiseLike<U>) | null | undefined): MyPromise<U>;
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}
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type InfinitePromise<T> = Promise<InfinitePromise<T>>;
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type P0 = Awaited<Promise<string | Promise<MyPromise<number> | null> | undefined>>;
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type P1 = Awaited<any>;
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type P2 = Awaited<InfinitePromise<number>>; // Error
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function f11<T, U extends T>(tx: T, ta: Awaited<T>, ux: U, ua: Awaited<U>) {
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ta = ua;
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ua = ta; // Error
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ta = tx; // Error
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tx = ta; // Error
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}
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// Flattening arrays
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type Flatten<T extends readonly unknown[]> = T extends unknown[] ? _Flatten<T>[] : readonly _Flatten<T>[];
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type _Flatten<T> = T extends readonly (infer U)[] ? _Flatten<U> : T;
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type InfiniteArray<T> = InfiniteArray<T>[];
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type B0 = Flatten<string[][][]>;
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type B1 = Flatten<string[][] | readonly (number[] | boolean[][])[]>;
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type B2 = Flatten<InfiniteArray<string>>;
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type B3 = B2[0]; // Error
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// Repeating tuples
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type TupleOf<T, N extends number> = N extends N ? number extends N ? T[] : _TupleOf<T, N, []> : never;
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type _TupleOf<T, N extends number, R extends unknown[]> = R['length'] extends N ? R : _TupleOf<T, N, [T, ...R]>;
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type TT0 = TupleOf<string, 4>;
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type TT1 = TupleOf<number, 0 | 2 | 4>;
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type TT2 = TupleOf<number, number>;
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type TT3 = TupleOf<number, any>;
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type TT4 = TupleOf<number, 100>; // Depth error
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function f22<N extends number, M extends N>(tn: TupleOf<number, N>, tm: TupleOf<number, M>) {
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tn = tm;
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tm = tn;
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}
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declare function f23<T>(t: TupleOf<T, 3>): T;
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f23(['a', 'b', 'c']); // string
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// Inference to recursive type
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interface Box<T> { value: T };
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type RecBox<T> = T | Box<RecBox<T>>;
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type InfBox<T> = Box<InfBox<T>>;
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declare function unbox<T>(box: RecBox<T>): T
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type T1 = Box<string>;
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type T2 = Box<T1>;
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type T3 = Box<T2>;
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type T4 = Box<T3>;
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type T5 = Box<T4>;
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type T6 = Box<T5>;
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declare let b1: Box<Box<Box<Box<Box<Box<string>>>>>>;
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declare let b2: T6;
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declare let b3: InfBox<string>;
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declare let b4: { value: { value: { value: typeof b4 }}};
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unbox(b1); // string
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unbox(b2); // string
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unbox(b3); // InfBox<string>
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unbox({ value: { value: { value: { value: { value: { value: 5 }}}}}}); // number
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unbox(b4); // { value: { value: typeof b4 }}
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unbox({ value: { value: { get value() { return this; } }}}); // { readonly value: ... }
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// Inference from nested instantiations of same generic types
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type Box1<T> = { value: T };
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type Box2<T> = { value: T };
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declare function foo<T>(x: Box1<Box1<T>>): T;
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declare let z: Box2<Box2<string>>;
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foo(z); // unknown, but ideally would be string (requires unique recursion ID for each type reference)
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// Intersect tuple element types
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type Intersect<U extends any[], R = unknown> = U extends [infer H, ...infer T] ? Intersect<T, R & H> : R;
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type QQ = Intersect<[string[], number[], 7]>;
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// Infer between structurally identical recursive conditional types
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type Unpack1<T> = T extends (infer U)[] ? Unpack1<U> : T;
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type Unpack2<T> = T extends (infer U)[] ? Unpack2<U> : T;
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function f20<T, U extends T>(x: Unpack1<T>, y: Unpack2<T>) {
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x = y;
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y = x;
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f20(y, x);
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}
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type Grow1<T extends unknown[], N extends number> = T['length'] extends N ? T : Grow1<[number, ...T], N>;
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type Grow2<T extends unknown[], N extends number> = T['length'] extends N ? T : Grow2<[string, ...T], N>;
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function f21<T extends number>(x: Grow1<[], T>, y: Grow2<[], T>) {
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f21(y, x); // Error
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}
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