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https://github.com/vercel-labs/scriptc.git
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Chris Tate
4d3ee3fffd
- Array patterns over strings split by code points via the string-iterator machinery: positions, holes, defaults, rest, nesting, and for-of heads - Destructured stdlib-global members bind their builtin identity tokens with Node-agreeing === identity; aliases register the twin - Surfaced-global members like Math.max fence eagerly by name — a token would quietly degrade them - Object patterns over strings bind length; wrapper-method extraction names the detached method # Conflicts: # packages/compiler/test/ts7/baselines/order-parity.json
73 lines
2.2 KiB
TypeScript
73 lines
2.2 KiB
TypeScript
// Destructuring DECLARATIONS from string sources. Array patterns walk
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// the STRING ITERATOR — code points, so astral characters stay whole
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// (the Array.from(string) machinery) — with holes, defaults (a bounds
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// test fires them past the last code point), rest (the remaining code
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// points pack fresh), and nested patterns. Object patterns read the
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// wrapper's one own data property, `length` — code UNITS, so an astral
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// character counts 2 — shorthand, renamed, and (dead-)defaulted.
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const s = "a😀c";
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const [x, y, z] = s;
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console.log(x, y, z);
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// Holes skip their position (one code point each, astral included).
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const [, mid] = "😀b";
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console.log(mid);
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// Defaults: dead in range, firing past the end — JS's undefined rule.
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const [d1 = "D1", d2 = "D2", d3 = "D3"] = "pq";
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console.log(d1, d2, d3);
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// A later default may read an earlier binding (left-to-right).
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const [h1, h2 = h1 + "!"] = "k";
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console.log(h1, h2);
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// Rest packs the remaining code points into a fresh string[].
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const [head, ...tail] = "x😀yz";
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console.log(head, tail.length, tail.join("|"));
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// A rest whose operand is itself an array pattern destructures the pack.
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const [...[r1, r2]] = "no";
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console.log(r1, r2);
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// Nested array patterns recurse into single code points.
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const [[inner], rest2] = "😀x";
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console.log(inner, rest2);
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// The wrapper's `length` — UTF-16 code units, so the astral pair is 2.
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const { length } = s;
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console.log(length);
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const { length: renamed } = "😀";
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console.log(renamed);
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const { length: dflt = 99 } = "ab";
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console.log(dflt);
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// Nested object patterns over array-pattern elements read the code
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// point's own length.
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const [{ length: first }] = "😀xy";
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console.log(first);
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// Parameter patterns ride the same lowerings.
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function width({ length: n }: string): number {
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return n;
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}
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function pair([a, b]: string): string {
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return b + a;
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}
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console.log(width("😀!"), pair("mn"));
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// for-of heads destructure each element string.
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for (const [c, ...cs] of ["ab", "😀z"]) {
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console.log(c, cs.join(""));
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}
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for (const { length: n } of ["", "😀"]) {
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console.log(n);
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}
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// A for-of DIRECTLY over a string destructures each code point.
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for (const [half] of "a😀") {
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console.log(half);
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}
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for (const { length: units } of "b😀") {
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console.log(units);
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}
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