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[acorn-opt] Use walkPattern for variable declarators too #24553

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Merged
merged 2 commits into from
Jun 12, 2025
Merged

[acorn-opt] Use walkPattern for variable declarators too #24553

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91e1e8e
[acorn-opt] Use walkPattern for variable declarators too
RReverser Jun 12, 2025
4ca0daf
Update JSDCE-objectPattern-output.js
RReverser Jun 12, 2025
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1 change: 0 additions & 1 deletion test/js_optimizer/JSDCE-objectPattern-output.js
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@ let z = 50;
globalThis.f = function([, r]) {
let {a, b} = r;
let {z: c} = r;
let [, i, {foo: p, bar: q}] = r;
return g(a, b, c, d, z);
};

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21 changes: 10 additions & 11 deletions tools/acorn-optimizer.mjs
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Expand Up @@ -243,17 +243,16 @@ function JSDCE(ast, aggressive) {
let removedHere = 0;
node.declarations = node.declarations.filter((node) => {
assert(node.type === 'VariableDeclarator');
const id = node.id;
if (id.type === 'ObjectPattern' || id.type === 'ArrayPattern') {
// TODO: DCE into object patterns, that is, things like
// let { a, b } = ..
// let [ a, b ] = ..
return true;
}
assert(id.type === 'Identifier');
const curr = id.name;
const value = node.init;
const keep = !names.has(curr) || (value && hasSideEffects(value));
let keep = node.init && hasSideEffects(node.init);
walkPattern(
node.id,
(value) => {
keep ||= hasSideEffects(value);
},
(boundName) => {
keep ||= !names.has(boundName);
},
);
if (!keep) removedHere = 1;
return keep;
});
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