fix: preserve shadowed for-loop declarators (#11242)

* fix: do not remove for-loop declarators

* fix: do not remove uninitialized var declarators in for init

packages/babel-plugin-transform-parameters/src/params.js

@@ -76,11 +76,19 @@ export default function convertFunctionParams(path, loose) {
           switch (node.type) {
             case "VariableDeclarator":
               if (node.init === null) {
-                redeclarator.remove();
-              } else {
-                state.iife = true;
+                const declaration = redeclarator.parentPath;
+                // The following uninitialized var declarators should not be removed
+                // for (var x in {})
+                // for (var x;;)
+                if (
+                  !declaration.parentPath.isFor() ||
+                  declaration.parentPath.get("body") === declaration
+                ) {
+                  redeclarator.remove();
+                  break;
+                }
               }
-              break;
+            // fall through
             case "FunctionDeclaration":
               state.iife = true;
               break;

packages/babel-plugin-transform-parameters/test/fixtures/parameters/let-for-init-same-as-param/exec.js

@@ -0,0 +1,5 @@
+function foo(a = 2) {
+  for (let a = 1; a > 0; a--);
+  expect(a).toBe(2);
+}
+foo();

packages/babel-plugin-transform-parameters/test/fixtures/parameters/let-no-init-for-init-same-as-param/exec.js

@@ -0,0 +1,5 @@
+function foo(a = 2) {
+  for (let a, i = 0; i < 1; i++) a = 1;
+  expect(a).toBe(2);
+}
+foo();

packages/babel-plugin-transform-parameters/test/fixtures/parameters/var-for-body-same-as-param/exec.js

@@ -0,0 +1,5 @@
+function foo(a = 2) {
+  for (var i of [0]) var a = 1;
+  expect(a).toBe(1);
+}
+foo();

packages/babel-plugin-transform-parameters/test/fixtures/parameters/var-for-init-same-as-param/exec.js

@@ -0,0 +1,5 @@
+function foo(a = 2) {
+  for (var [a] of [[1]]);
+  expect(a).toBe(1);
+}
+foo();

packages/babel-plugin-transform-parameters/test/fixtures/parameters/var-no-init-for-body-same-as-param/exec.js

@@ -0,0 +1,5 @@
+function foo(a = 2) {
+  for (var i of [0]) var a;
+  expect(a).toBe(2);
+}
+foo();

packages/babel-plugin-transform-parameters/test/fixtures/parameters/var-no-init-for-init-same-as-param/exec.js

@@ -0,0 +1,5 @@
+function foo(a = 2) {
+  for (var a, i = 0; i < 1; i++);
+  expect(a).toBe(undefined);
+}
+foo();

packages/babel-plugin-transform-parameters/test/fixtures/regression/11231/input.mjs

@@ -0,0 +1,3 @@
+(i = "__proto__") => {
+  for (var i in {});
+};

packages/babel-plugin-transform-parameters/test/fixtures/regression/11231/options.json

@@ -0,0 +1,5 @@
+{
+  "plugins": [
+    "transform-parameters"
+  ]
+}

packages/babel-plugin-transform-parameters/test/fixtures/regression/11231/output.mjs

@@ -0,0 +1,6 @@
+(function () {
+  let i = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : "__proto__";
+  return function () {
+    for (var i in {});
+  }();
+});