Do not evaluate the initializers of for-in and for-of. Closes #1234

terser · Apr 19, 2023 · e072c21 · e072c21
1 parent 7093b30
commit e072c21
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diff --git a/lib/compress/inference.js b/lib/compress/inference.js
@@ -64,6 +64,7 @@ import {
   AST_EmptyStatement,
   AST_Expansion,
   AST_False,
+  AST_ForIn,
   AST_Function,
   AST_If,
   AST_Import,
@@ -712,6 +713,7 @@ export function is_nullish(node, compressor) {
 export function is_lhs(node, parent) {
     if (parent instanceof AST_Unary && unary_side_effects.has(parent.operator)) return parent.expression;
     if (parent instanceof AST_Assign && parent.left === node) return node;
+    if (parent instanceof AST_ForIn && parent.init === node) return node;
 }
 
 (function(def_find_defs) {

diff --git a/test/compress/loops.js b/test/compress/loops.js
@@ -758,3 +758,14 @@ issue_2904: {
     }
     expect_stdout: "1"
 }
+
+issue_t1234: {
+    options = {}
+    input: {
+        for ({ x: 0 }.x of [1, 2]) console.log(123);
+    }
+    expect: {
+        for ({ x: 0 }.x of [1, 2]) console.log(123);
+    }
+    expect_stdout: ["123", "123"]
+}