mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-11-04 08:04:37 +08:00
Malte Ubl
512282fa92
A literal holding a value that may be missing at run time (and the item arrays of push/unshift/toSpliced with such values) starts from an empty array and stores each element with a state test. The empty array had no dense storage, so the first store always took the runtime path and grew the array. arrayLit gains an optional capacity hint (validated: an integer between the element count and 1024, no observable effect) that the emitter passes to the allocation; these builders set it to the number of plain elements, so the stores stay on the inline dense path. tsc-ts hits this in getOptionalType's `[t, missingOrUndefined]`.
53 lines
1.6 KiB
TypeScript
53 lines
1.6 KiB
TypeScript
// Array literals and argument lists holding values that may be holes or
|
|
// missing reads: present values keep their identity, missing ones become
|
|
// present undefined, spreads and holes keep their positions, and the
|
|
// literal's length and contents match Node.
|
|
|
|
class Ty {
|
|
name: string;
|
|
constructor(name: string) {
|
|
this.name = name;
|
|
}
|
|
}
|
|
|
|
function show(list: readonly Ty[]): string {
|
|
const parts: string[] = [];
|
|
for (let i = 0; i < list.length; i++) {
|
|
parts.push(i in list ? (list[i] === undefined ? "undef" : list[i]!.name) : "hole");
|
|
}
|
|
return `${list.length}:[${parts.join(",")}]`;
|
|
}
|
|
|
|
const undef = new Ty("undefined");
|
|
const source: Ty[] = [new Ty("a")];
|
|
source[2] = new Ty("c");
|
|
|
|
// Literals mixing optional values and spreads.
|
|
for (const t of source) {
|
|
const built: Ty[] = [t, ...source, t, undef];
|
|
console.log("mixed", show(built));
|
|
}
|
|
|
|
// Item arrays for unshift and toSpliced.
|
|
for (const t of source) {
|
|
const front: Ty[] = [undef];
|
|
front.unshift(t, undef, t);
|
|
const copy = source.toSpliced(1, 1, t, undef);
|
|
console.log("items", show(front), show(copy), show(source));
|
|
}
|
|
|
|
// Numbers and strings.
|
|
const nums: number[] = [1];
|
|
nums[2] = 3;
|
|
for (const n of nums) console.log("nums", JSON.stringify([n, n, 0]));
|
|
const words: string[] = ["x"];
|
|
words[2] = "z";
|
|
console.log("words", JSON.stringify([words[0]!, words[1]!, words[2]!, ...words]));
|
|
|
|
// Larger literal with optional values keeps every element.
|
|
const many = [
|
|
source[0]!, source[1]!, source[2]!, source[3]!, source[0]!, source[1]!,
|
|
source[2]!, source[3]!, source[0]!, source[1]!, source[2]!, source[3]!,
|
|
];
|
|
console.log("many", show(many));
|