From cc30d826b3f55b7c0f6d495a924a7852c7529b3c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Wed, 9 Nov 2022 13:55:32 +0100
Subject: [PATCH 1/2] Add failing test

---
 .../test/fixtures/general/switch-shadow/input.js             | 3 +++
 .../test/fixtures/general/switch-shadow/output.js            | 4 ++++
 .../test/fixtures/tdz/switch-shadow/input.js                 | 4 ++++
 .../test/fixtures/tdz/switch-shadow/output.js                | 5 +++++
 4 files changed, 16 insertions(+)
 create mode 100644 packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/input.js
 create mode 100644 packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/output.js
 create mode 100644 packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/input.js
 create mode 100644 packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/output.js

diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/input.js
new file mode 100644
index 000000000000..7a7a289aba67
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/input.js
@@ -0,0 +1,3 @@
+switch (x) {
+  default: let x;
+}
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/output.js
new file mode 100644
index 000000000000..65726dfc6ba1
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/output.js
@@ -0,0 +1,4 @@
+switch (x) {
+  default:
+    var x;
+}
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/input.js
new file mode 100644
index 000000000000..1ba4bd251964
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/input.js
@@ -0,0 +1,4 @@
+let x;
+switch (x) {
+  default: let x;
+}
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/output.js
new file mode 100644
index 000000000000..f03f42298578
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/output.js
@@ -0,0 +1,5 @@
+var x;
+switch (babelHelpers.tdz("x")) {
+  default:
+    var _x;
+}

From ba474c64b78f1097187434eb2afa571a44d4005f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Wed, 9 Nov 2022 14:08:25 +0100
Subject: [PATCH 2/2] Register `switch`'s `discriminant` in the outer scope

---
 .../test/fixtures/general/switch-shadow/output.js         | 2 +-
 .../test/fixtures/tdz/switch-shadow/output.js             | 2 +-
 packages/babel-traverse/src/path/context.ts               | 8 +++++---
 packages/babel-traverse/test/scope.js                     | 8 ++++++++
 4 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/output.js
index 65726dfc6ba1..95cdac755c6b 100644
--- a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/output.js
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/switch-shadow/output.js
@@ -1,4 +1,4 @@
 switch (x) {
   default:
-    var x;
+    var _x;
 }
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/output.js
index f03f42298578..36f5e171d618 100644
--- a/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/output.js
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/tdz/switch-shadow/output.js
@@ -1,5 +1,5 @@
 var x;
-switch (babelHelpers.tdz("x")) {
+switch (x) {
   default:
     var _x;
 }
diff --git a/packages/babel-traverse/src/path/context.ts b/packages/babel-traverse/src/path/context.ts
index de5d4bbc7d35..6fb9f5047ddc 100644
--- a/packages/babel-traverse/src/path/context.ts
+++ b/packages/babel-traverse/src/path/context.ts
@@ -133,10 +133,12 @@ export function setScope(this: NodePath) {
 
   let path = this.parentPath;
 
-  // Skip method scope if is computed method key or decorator expression
   if (
-    (this.key === "key" || this.listKey === "decorators") &&
-    path.isMethod()
+    // Skip method scope if is computed method key or decorator expression
+    ((this.key === "key" || this.listKey === "decorators") &&
+      path.isMethod()) ||
+    // Skip switch scope if for discriminant (`x` in `switch (x) {}`).
+    (this.key === "discriminant" && path.isSwitchStatement())
   ) {
     path = path.parentPath;
   }
diff --git a/packages/babel-traverse/test/scope.js b/packages/babel-traverse/test/scope.js
index 612e7046b3d4..30aacd61566b 100644
--- a/packages/babel-traverse/test/scope.js
+++ b/packages/babel-traverse/test/scope.js
@@ -282,6 +282,14 @@ describe("scope", () => {
       });
     });
 
+    it("switch discriminant scope", () => {
+      expect(
+        getPath(`let a = "outside"; switch (a) { default: let a = "inside" }`)
+          .get("body.1.discriminant")
+          .scope.getBinding("a").path.node.init.value,
+      ).toBe("outside");
+    });
+
     it("variable declaration", function () {
       expect(getPath("var foo = null;").scope.getBinding("foo").path.type).toBe(
         "VariableDeclarator",