From add64e870bef076c3e42f68fd8a05ac9467fdbe1 Mon Sep 17 00:00:00 2001
From: Sneh Khatri <khatris2014@gmail.com>
Date: Mon, 13 Dec 2021 22:59:10 +0530
Subject: [PATCH] Don't resolve shadowed `arguments` variables from functions
 (#14036)

---
 .../arguments-global-var/output.js             |  2 +-
 .../implicit-var-arguments/exec.js             | 11 +++++++++++
 .../implicit-var-arguments/input.js            | 10 ++++++++++
 .../implicit-var-arguments/options.json        |  4 ++++
 .../implicit-var-arguments/output.js           | 18 ++++++++++++++++++
 packages/babel-traverse/src/scope/index.ts     |  7 +++++++
 6 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/exec.js
 create mode 100644 packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/input.js
 create mode 100644 packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/options.json
 create mode 100644 packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/output.js

diff --git a/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/arguments-global-var/output.js b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/arguments-global-var/output.js
index f19432c82500..e458a2d298d9 100644
--- a/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/arguments-global-var/output.js
+++ b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/arguments-global-var/output.js
@@ -1,7 +1,7 @@
 var _arguments2 = 1;
 
 function fn() {
-  var _arguments = _arguments2;
+  var _arguments = arguments;
 
   var foo = function () {
     return _arguments;
diff --git a/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/exec.js b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/exec.js
new file mode 100644
index 000000000000..428e0f6986b2
--- /dev/null
+++ b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/exec.js
@@ -0,0 +1,11 @@
+var arguments = [1, 2, 3];
+var arr = () => arguments[0];
+
+expect(arr()).toStrictEqual(1)
+
+function foo(n) {
+var f = () => arguments[0] + n; // foo's implicit arguments binding. arguments[0] is n
+return f();
+}
+ 
+expect(foo(3)).toStrictEqual(6)
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/input.js b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/input.js
new file mode 100644
index 000000000000..31a30fd84854
--- /dev/null
+++ b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/input.js
@@ -0,0 +1,10 @@
+var arguments = [1, 2, 3];
+var arr = (n) => arguments[0];
+
+arr(4); // 1
+
+function foo(n) {
+var f = () => arguments[0] + n; // foo's implicit arguments binding. arguments[0] is n
+return f();
+}
+ 
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/options.json b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/options.json
new file mode 100644
index 000000000000..7e8d4deeee4a
--- /dev/null
+++ b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/options.json
@@ -0,0 +1,4 @@
+{
+  "sourceType": "script",
+  "plugins": ["transform-arrow-functions"]
+}
diff --git a/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/output.js b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/output.js
new file mode 100644
index 000000000000..b23abd2158c6
--- /dev/null
+++ b/packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/implicit-var-arguments/output.js
@@ -0,0 +1,18 @@
+var _arguments = [1, 2, 3];
+
+var arr = function (n) {
+  return _arguments[0];
+};
+
+arr(4); // 1
+
+function foo(n) {
+  var _arguments2 = arguments;
+
+  var f = function () {
+    return _arguments2[0] + n;
+  }; // foo's implicit arguments binding. arguments[0] is n
+
+
+  return f();
+}
diff --git a/packages/babel-traverse/src/scope/index.ts b/packages/babel-traverse/src/scope/index.ts
index e2eb17d8f724..71e43ebb005f 100644
--- a/packages/babel-traverse/src/scope/index.ts
+++ b/packages/babel-traverse/src/scope/index.ts
@@ -1138,6 +1138,13 @@ export default class Scope {
         } else {
           return binding;
         }
+      } else if (
+        !binding &&
+        name === "arguments" &&
+        scope.path.isFunction() &&
+        !scope.path.isArrowFunctionExpression()
+      ) {
+        break;
       }
       previousPath = scope.path;
     } while ((scope = scope.parent));