Destructuring: Create assignments from ForX non-declaration patterns (#9414)

packages/babel-plugin-proposal-object-rest-spread/src/index.js

@@ -377,10 +377,16 @@ export default declare((api, opts) => {
 
           path.ensureBlock();
 
+          if (node.body.body.length === 0 && path.isCompletionRecord()) {
             node.body.body.unshift(
-            t.variableDeclaration("var", [
+              t.expressionStatement(scope.buildUndefinedNode()),
-              t.variableDeclarator(left, t.cloneNode(temp)),
+            );
-            ]),
+          }
+
+          node.body.body.unshift(
+            t.expressionStatement(
+              t.assignmentExpression("=", left, t.cloneNode(temp)),
+            ),
           );
 
           return;

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-rest/for-x-completion-record/input.js

@@ -0,0 +1 @@
+for ({a, ...b} of []) {}

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-rest/for-x-completion-record/output.js

@@ -0,0 +1,9 @@
+for (var _ref of []) {
+  var _ref2 = _ref;
+  ({
+    a
+  } = _ref2);
+  b = babelHelpers.objectWithoutProperties(_ref2, ["a"]);
+  _ref2;
+  void 0;
+}

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-rest/for-x/output.js

@@ -7,18 +7,22 @@ for (var _ref of []) {
 }
 
 for (var _ref2 of []) {
-  var {
+  var _ref3 = _ref2;
+  ({
     a
-  } = _ref2,
+  } = _ref3);
-      b = babelHelpers.objectWithoutProperties(_ref2, ["a"]);
+  b = babelHelpers.objectWithoutProperties(_ref3, ["a"]);
+  _ref3;
 }
 
 async function a() {
-  for await (var _ref3 of []) {
+  for await (var _ref4 of []) {
-    var {
+    var _ref5 = _ref4;
+    ({
       a
-    } = _ref3,
+    } = _ref5);
-        b = babelHelpers.objectWithoutProperties(_ref3, ["a"]);
+    b = babelHelpers.objectWithoutProperties(_ref5, ["a"]);
+    _ref5;
   }
 } // skip
 

packages/babel-plugin-transform-destructuring/src/index.js

@@ -449,8 +449,14 @@ export default declare((api, options) => {
 
           path.ensureBlock();
 
+          if (node.body.body.length === 0 && path.isCompletionRecord()) {
             node.body.body.unshift(
-            t.variableDeclaration("var", [t.variableDeclarator(left, temp)]),
+              t.expressionStatement(scope.buildUndefinedNode()),
+            );
+          }
+
+          node.body.body.unshift(
+            t.expressionStatement(t.assignmentExpression("=", left, temp)),
           );
 
           return;

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

@@ -1,3 +1,7 @@
 for (var [name, value] in obj) {
   print("Name: " + name + ", Value: " + value);
 }
+
+for ([name, value] in obj) {
+  print("Name: " + name + ", Value: " + value);
+}

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

@@ -5,3 +5,11 @@ for (var _ref in obj) {
   var value = _ref2[1];
   print("Name: " + name + ", Value: " + value);
 }
+
+for (var _ref3 in obj) {
+  var _ref4 = babelHelpers.slicedToArray(_ref3, 2);
+
+  name = _ref4[0];
+  value = _ref4[1];
+  print("Name: " + name + ", Value: " + value);
+}

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

@@ -1,3 +1,7 @@
 for (var [ name, before, after ] of test.expectation.registers) {
 
 }
+
+for ([ name, before, after ] of test.expectation.registers) {
+
+}

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

@@ -5,3 +5,12 @@ for (var _ref of test.expectation.registers) {
   var before = _ref2[1];
   var after = _ref2[2];
 }
+
+for (var _ref3 of test.expectation.registers) {
+  var _ref4 = babelHelpers.slicedToArray(_ref3, 3);
+
+  name = _ref4[0];
+  before = _ref4[1];
+  after = _ref4[2];
+  void 0;
+}