mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-11-02 07:43:42 +08:00
Chris Tate
0725682c87
A JavaScript object pattern over an untyped source (the result of an untyped function, a parameter, a property of an untyped object) now checks the source first when V8 can spell it, as the `any` path in TypeScript files does: a null or undefined source throws "Cannot destructure property 'size' of 'lookup(...)' as it is null." instead of "Cannot read properties of null (reading 'size')". When the first element has a default and a static key (`{ size = 0 }`), the source is not checked first and the read throws, as in V8; this also applies to `any` sources in TypeScript files and to nullable union sources.
104 lines
2.9 KiB
JavaScript
104 lines
2.9 KiB
JavaScript
// A destructuring declaration whose source is one object or array type or
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// null/undefined (`s.match(re)`, `items.find(...)`) throws Node's TypeError
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// when the source is null or undefined, with V8's message for the source
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// spelling, and binds normally otherwise.
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function show(label, fn) {
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try {
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fn();
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} catch (error) {
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console.log(label, error instanceof TypeError, error.message);
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}
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}
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const text = "abc";
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show("object-call", () => {
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const { index } = text.match(/z/);
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console.log("never", index);
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});
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show("object-empty", () => {
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const {} = text.match(/z/);
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console.log("never");
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});
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show("object-identifier", () => {
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const found = "abc".match(/z/);
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const { index, input } = found;
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console.log("never", index, input);
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});
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show("object-string-key", () => {
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const found = "abc".match(/z/);
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const { "index": at } = found;
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console.log("never", at);
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});
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show("array-method-call", () => {
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const [whole] = "abc".match(/z/);
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console.log("never", whole);
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});
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show("array-identifier", () => {
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const found = "abc".match(/z/);
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const [whole, group] = found;
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console.log("never", whole, group);
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});
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const items = [
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{ name: "a", size: 1 },
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{ name: "b", size: 2 },
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];
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show("object-undefined", () => {
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const { name } = items.find((item) => item.size > 5);
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console.log("never", name);
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});
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// A default on the first element: V8 reads that key without checking
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// the source first, so the read's TypeError is the one thrown.
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show("object-first-default", () => {
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const { name = "none", size } = items.find((item) => item.size > 5);
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console.log("never", name, size);
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});
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show("object-later-default", () => {
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const { name, size = 0 } = items.find((item) => item.size > 5);
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console.log("never", name, size);
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});
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function firstMatch(text) {
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return text.match(/q/);
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}
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show("array-function-call", () => {
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const [first] = firstMatch("abc");
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console.log("never", first);
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});
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// A source that may be null or undefined, and data arms holding a
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// generator, which has no untyped form.
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function* count() {
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yield 1;
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yield 2;
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}
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function pick(kind) {
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if (kind === 0) return null;
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if (kind === 1) return undefined;
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return { counter: count(), label: "picked" };
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}
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function counters(present) {
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return present ? [count(), count()] : null;
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}
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show("object-null-arm", () => {
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const { counter } = pick(0);
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console.log("never", counter);
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});
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show("object-undefined-arm", () => {
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const { label } = pick(1);
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console.log("never", label);
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});
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show("array-generator-elements", () => {
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const [first] = counters(false);
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console.log("never", first);
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});
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const { counter, label } = pick(2);
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const [left, right] = counters(true);
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console.log(label, [...counter].join(","), [...left, ...right].join(","));
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// Sources that hold a value bind as before.
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const { index } = "abc".match(/b/);
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const [whole] = "abc".match(/c/);
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const { name, size } = items.find((item) => item.size > 1);
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console.log("bound", index, whole, name, size);
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