fix: Destructuring empty in nested for expressions (#14841)

* fix

* Update packages/babel-plugin-transform-destructuring/src/util.ts

Co-authored-by: Huáng Jùnliàng <jlhwung@gmail.com>

* review

* review

Co-authored-by: Huáng Jùnliàng <jlhwung@gmail.com>

packages/babel-plugin-transform-destructuring/src/util.ts

@@ -327,7 +327,6 @@ export class DestructuringTransformer {
         }
       }
     }
-    //
 
     for (let i = 0; i < pattern.properties.length; i++) {
       const prop = pattern.properties[i];
@@ -484,8 +483,6 @@ export class DestructuringTransformer {
       }
     }
 
-    //
-
     this.push(pattern, ref);
 
     return this.nodes;
@@ -620,6 +617,8 @@ export function convertVariableDeclaration(
     }
   }
 
+  const inForInit = t.isForStatement(path.parent, { init: node });
+
   let tail: t.VariableDeclaration | null = null;
   const nodesOut = [];
   for (const node of nodes) {
@@ -640,7 +639,9 @@ export function convertVariableDeclaration(
     if (!node.loc) {
       node.loc = nodeLoc;
     }
-    nodesOut.push(node);
+    nodesOut.push(
+      inForInit && node.type === "ExpressionStatement" ? node.expression : node,
+    );
   }
 
   if (nodesOut.length === 1) {

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/destructuring-empty-in-for/input.js

@@ -0,0 +1,5 @@
+for ( let x in y ) for ( ; ; ) var { } = x ;
+
+for ( let x in y ) for ( var { } = x ; ; ) ;
+
+for ( let x in y ) for ( ; { } = x ; {} = x ) var { } = x ;

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/destructuring-empty-in-for/output.js

@@ -0,0 +1,19 @@
+for (var x in y) {
+  for (;;) {
+    babelHelpers.objectDestructuringEmpty(x);
+  }
+}
+
+for (var _x in y) {
+  for (babelHelpers.objectDestructuringEmpty(_x);;) {
+    ;
+  }
+}
+
+for (var _x2 in y) {
+  for (; _x3 = _x2, babelHelpers.objectDestructuringEmpty(_x3), _x3; _x4 = _x2, babelHelpers.objectDestructuringEmpty(_x4), _x4) {
+    var _x3, _x4;
+
+    babelHelpers.objectDestructuringEmpty(_x2);
+  }
+}