mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-10-02 08:35:07 +08:00
Chris Tate
e517a251ae
- Preserve class property views, opaque record identity, and nullable structural conversions - Run package metadata transforms and TypeScript option merges as native code - Serialize live typed records with opaque payloads and JSON hooks
49 lines
2.2 KiB
TypeScript
49 lines
2.2 KiB
TypeScript
// @transform-types
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type Failure = { degrade: string };
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function rewrite(answer: string | Failure | null, projected: string | undefined): string | undefined {
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if (answer !== null && typeof answer === "object") return answer.degrade;
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return answer ?? projected;
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}
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console.log(rewrite("", "fallback"), rewrite(null, "fallback"), rewrite({ degrade: "reason" }, undefined));
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console.log(rewrite(null, undefined) === undefined);
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const events: string[] = [];
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function fallback(value: number | undefined): number | undefined { events.push("fallback"); return value; }
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function withNumber(value: string | Failure | null | undefined): string | number | undefined {
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if (value !== null && typeof value === "object") return value.degrade;
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return value ?? fallback(7);
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}
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console.log(withNumber("kept"), events.join(","));
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console.log(withNumber(null), events.join(","));
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console.log(withNumber(undefined), events.join(","));
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console.log(withNumber(""), events.join(","));
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function retainFalsy(value: boolean | number | Failure | undefined): boolean | number | string {
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if (typeof value === "object") return value.degrade;
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return value ?? "missing";
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}
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console.log(retainFalsy(false), retainFalsy(0), retainFalsy(2), retainFalsy(undefined));
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let calls = 0;
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function effectful(value: string | null): string | null { calls++; return value; }
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function widen(value: string | null): string | number | undefined {
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return effectful(value) ?? fallback(undefined);
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}
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console.log(widen("once"), calls, events.length);
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console.log(widen(null) === undefined, calls, events.length);
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class Item { constructor(readonly id: number) {} }
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function choose(value: Item | string | null, replacement: Item | undefined): Item | undefined {
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if (typeof value === "string") return replacement;
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return value ?? replacement;
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}
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const item = new Item(9);
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console.log(choose(item, undefined) === item, choose(null, item) === item);
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interface Wide { value: number; extra: string }
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interface Narrow { value: number }
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function copy(value: Wide | null, replacement: Narrow | undefined): Narrow | undefined {
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return value ?? replacement;
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}
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console.log(copy({ value: 4, extra: "discarded" }, undefined)?.value, copy(null, { value: 6 })?.value);
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