mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-11-01 07:33:12 +08:00
Chris Tate
e80b5f1447
`.length` of a tuple is its arity, and the lowering folded it to that constant only when the receiver was rooted at a binding or `this`. Any other receiver (a call result, a ternary, an `as` assertion, an `as const` literal) was refused with SC1090. The receiver is now evaluated once, for its side effects and exceptions, and its value discarded; the expression is the arity. A binding, `this`, or a chain of plain property reads from one still folds. A chain through an accessor is evaluated, so an accessor that returns a tuple runs, as in Node.
34 lines
1.4 KiB
TypeScript
34 lines
1.4 KiB
TypeScript
// Tuple + ref-element-array fences — what stays OUT of the new surface and
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// why: dynamic tuple index WRITES, optional/rest tuple elements (no fixed shape), variable-length
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// spreads into tuple literals, join on ref-element arrays (JS would
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// recursively toString). Map-element arrays now use reference storage;
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// keep them here as accepted adjacent coverage.
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const pair: [string, number] = ["a", 1];
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// Dynamic index: a READ dispatches over the positions (undefined off the
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// end, as Node); a WRITE still needs the literal-index shape.
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let i = 0;
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console.log(pair[i]);
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pair[i] = "b";
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// Optional and rest elements have no fixed arity/shape.
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const opt: [string, number?] = ["x"];
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const rest: [string, ...number[]] = ["y", 1, 2];
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// Heterogeneous tuples ITERATE now (positions snapshot into the union),
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// and the union-typed loop variable PRINTS (per-arm console rendering).
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for (const part of pair) {
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console.log(part);
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}
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// An array's runtime length cannot determine a fixed tuple's positions.
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const copy = [...(["a", 1] as (string | number)[])] as [string, number];
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// join on ref-element arrays: JS would recursively toString — dishonest.
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const recs: { id: number }[] = [{ id: 1 }];
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console.log(recs.join(","));
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const tuples: [string, string][] = [["k", "v"]];
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console.log(tuples.join(";"));
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// Map elements compile through the same REF storage as function elements.
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const maps: Map<string, number>[] = [];
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