mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-10-23 06:10:02 +08:00
Chris Tate
057ac2cea2
- 2530-2535 and 2541 lock in the destructuring forms the static tier already compiled but the corpus never pinned: object/array/tuple declarations (renames, defaults, holes, nesting, fresh rest tails), the options-object parameter pattern (element and whole-pattern defaults, tuple/rest parameter patterns), for-of heads (containers, defaults, rest, existing bindings), object rest freshness and key order, assignment basics (swaps, chains, expression value), and evaluation order (RHS once, elements left to right, lazy defaults that see earlier bindings). - All byte-identical against Node under both backends, and each reports 100% static coverage.
59 lines
1.7 KiB
TypeScript
59 lines
1.7 KiB
TypeScript
// Evaluation order under destructuring, pinned against Node: the RHS
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// evaluates ONCE, elements read left to right at their pattern
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// positions, defaults evaluate lazily (only on undefined, in element
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// order), and rest packs after the named elements consumed.
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let log: string[] = [];
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function traced<T>(tag: string, value: T): T {
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log.push(tag);
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return value;
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}
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// The source expression evaluates once, before any element.
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function makeSource(): { a: number; b: number } {
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log.push("src");
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return { a: 1, b: 2 };
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}
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const { a, b } = makeSource();
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console.log(a, b, log.join(","));
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log = [];
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// Defaults evaluate in element order, only when needed, and later
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// defaults see earlier bindings.
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const partial: { p?: number; q?: number; r?: number } = { q: 5 };
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const { p = traced("p", 10), q = traced("q", 20), r = traced("r", p + q) } = partial;
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console.log(p, q, r, log.join(","));
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log = [];
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// Array positions consume left to right; holes skip without reading.
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const seq = [traced("e0", 1), traced("e1", 2), traced("e2", 3)];
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log = [];
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const [, s1, s2 = traced("dflt", -1)] = seq;
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console.log(s1, s2, log.join(",") === "" ? "(no default ran)" : log.join(","));
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log = [];
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// Assignment position: the RHS still evaluates once, then targets
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// assign in source order.
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let m = 0;
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let n = 0;
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function pair(): [number, number] {
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log.push("pair");
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return [7, 8];
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}
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[m, n] = pair();
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console.log(m, n, log.join(","));
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log = [];
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// Getter sources read at each element's own position, left to right.
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let tick = 0;
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const stream = {
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get pull(): number {
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tick += 1;
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log.push(`pull${tick}`);
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return tick;
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},
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fixed: 100,
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};
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const { fixed, pull } = stream;
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const { pull: pullAgain } = stream;
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console.log(fixed, pull, pullAgain, log.join(","));
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