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

RealColdFry · web-flow · commit 781db8421db0 · 2026-04-16T22:01:34.000+02:00
* fix array destructuring not preserving evaluation order with side effects (#1405) * add more test cases for array destructuring side effects
diff --git a/src/transformation/visitors/variable-declaration.ts b/src/transformation/visitors/variable-declaration.ts
@@ -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,
@@ -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 {
diff --git a/test/unit/destructuring.spec.ts b/test/unit/destructuring.spec.ts
@@ -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"];
