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fix array destructuring prefix operator side effects (#1405) #1708

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fix array destructuring prefix operator side effects (#1405) #1708

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9711ecc
fix array destructuring not preserving evaluation order with side eff…
RealColdFry Apr 14, 2026
556cd1f
add more test cases for array destructuring side effects
RealColdFry Apr 14, 2026
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4 changes: 2 additions & 2 deletions src/transformation/visitors/variable-declaration.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ import { createCallableTable, isFunctionTypeWithProperties } from "./function";
import { transformIdentifier } from "./identifier";
import { isMultiReturnCall } from "./language-extensions/multi";
import { transformPropertyName } from "./literal";
import { moveToPrecedingTemp } from "./expression-list";
import { moveToPrecedingTemp, transformExpressionList } from "./expression-list";

export function transformArrayBindingElement(
context: TransformationContext,
Expand Down Expand Up @@ -205,7 +205,7 @@ export function transformBindingVariableDeclaration(
// Don't unpack array literals
const values =
initializer.elements.length > 0
? initializer.elements.map(e => context.transformExpression(e))
? transformExpressionList(context, initializer.elements)
: lua.createNilLiteral();
statements.push(...createLocalOrExportedOrGlobalDeclaration(context, vars, values, initializer));
} else {
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27 changes: 27 additions & 0 deletions test/unit/destructuring.spec.ts
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Expand Up @@ -226,6 +226,33 @@ describe("array destructuring optimization", () => {
.expectToMatchJsResult();
});

test("array literal with side effects in elements", () => {
util.testFunction`
const arr = [1, 2];
let i = 0;
let [v1, v2] = [arr[i], arr[++i]];
return { v1, v2 };
`.expectToMatchJsResult();
});

test("array literal with many side effects in elements", () => {
util.testFunction`
const arr = [10, 20, 30, 40];
let i = 0;
let [v1, v2, v3, v4] = [arr[i++], arr[i++], arr[i++], arr[i++]];
return { v1, v2, v3, v4 };
`.expectToMatchJsResult();
});

test("array literal with mixed pure and impure elements", () => {
util.testFunction`
const arr = [10, 20, 30];
let i = 0;
let [v1, v2, v3] = [1, arr[++i], 2];
return { v1, v2, v3, i };
`.expectToMatchJsResult();
});

test("array union", () => {
util.testFunction`
const array: [string] | [] = ["bar"];
Expand Down
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