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Malte UblandClaude Opus 5.5
cfb50d16e2
Higher-order wrappers over `(...args: any) => any` that forward `arguments` with `fn.apply(this, arguments)` and type their options with `Parameters<F>` / `ReturnType<F>`, and their rest-tuple rewrite, did not compile. Generic calls already monomorphize per call site; these pieces now resolve to that site's concrete signature: - Rest parameters typed as fixed tuples (`...args: [A, B]`, `...args: A` bound to a tuple, `...args: Parameters<F>`) flatten to positional parameters, so `(...args: [A, B]) => R` and `(a: A, b: B) => R` share one function type. Trailing optional positions become `T | undefined` slots. - `Parameters<F>`, `ReturnType<F>`, `Awaited<ReturnType<F>>` and the `ReturnType<F> extends PromiseLike<infer U> ? U : …` spelling resolve through F's binding. - A parameterless function expression reading `arguments` lowers against the fixed signature its value is asserted to (or contextually typed as); `arguments` is that signature's tuple. - `f.apply(thisArg, args)` and `f(...args)` over a forwarded tuple call directly, passing `thisArg` as the receiver. A tuple that is only forwarded is never allocated. - `fn.name` on a function parameter folds to the call site's static name; the instantiation key carries it. Also: optional callback fields narrowed at the call (`o.cb ? o.cb(x) : …`) compile, effect-free surplus arguments to fixed-arity function values are dropped, and `arguments.length` no longer counts a `this` parameter. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
47 lines
1.2 KiB
TypeScript
47 lines
1.2 KiB
TypeScript
// Variadic generic wrappers on methods: the wrapper passes its own `this`
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// through `fn.apply(this, arguments)`, so a wrapped `function (this: C)`
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// stored as a class property sees the receiver it was called on.
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type AnyFn = (...args: any) => any;
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function logged<F extends AnyFn>(fn: F, label: string): F {
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return function (this: unknown) {
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console.log(`[${label}] call with ${arguments.length} args`);
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return fn.apply(this, arguments as any);
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} as F;
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}
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class Counter {
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count = 0;
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step: number;
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constructor(step: number) {
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this.step = step;
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}
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bump = logged(function (this: Counter, times: number): number {
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this.count += this.step * times;
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return this.count;
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}, "bump");
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reset = logged((): void => {
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this.count = 0;
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}, "reset");
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}
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const c = new Counter(5);
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console.log(c.bump(1));
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console.log(c.bump(2));
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c.reset();
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console.log(c.count);
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class Repo {
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base: string;
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constructor(base: string) {
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this.base = base;
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}
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load = logged(async function (this: Repo, id: string): Promise<string> {
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await Promise.resolve();
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return `${this.base}/${id}`;
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}, "load");
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}
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const repo = new Repo("https://x.test");
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repo.load("7").then((url) => console.log("loaded", url));
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