From a7c82bdfa98f6825143b7afba03d28d325e4a718 Mon Sep 17 00:00:00 2001
From: CPunisher <1343316114@qq.com>
Date: Fri, 12 Jul 2024 21:03:50 +0800
Subject: [PATCH] fix(es/minifier): Fix variable declaration in default branch
 (#9220)

**Description:**

When a default branch appears before an exact match, the variable declaration should be recorded before deleting the default branch.

**Related issue:**

 - Closes https://github.com/swc-project/swc/issues/8919
---
 .../src/compress/optimize/switches.rs                 |  9 ++++++++-
 .../tests/fixture/issues/8919/input.js                | 11 +++++++++++
 .../tests/fixture/issues/8919/output.js               |  2 ++
 3 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 crates/swc_ecma_minifier/tests/fixture/issues/8919/input.js
 create mode 100644 crates/swc_ecma_minifier/tests/fixture/issues/8919/output.js

diff --git a/crates/swc_ecma_minifier/src/compress/optimize/switches.rs b/crates/swc_ecma_minifier/src/compress/optimize/switches.rs
index 5b5dab03bcc0..95831bf6473b 100644
--- a/crates/swc_ecma_minifier/src/compress/optimize/switches.rs
+++ b/crates/swc_ecma_minifier/src/compress/optimize/switches.rs
@@ -86,7 +86,14 @@ impl Optimizer<'_> {
 
             if !may_match_other_than_exact {
                 // remove default if there's an exact match
-                cases.retain(|case| case.test.is_some());
+                cases.retain(|case| {
+                    if case.test.is_some() {
+                        true
+                    } else {
+                        var_ids.extend(case.cons.extract_var_ids());
+                        false
+                    }
+                });
             }
 
             if cases.len() == 2 {
diff --git a/crates/swc_ecma_minifier/tests/fixture/issues/8919/input.js b/crates/swc_ecma_minifier/tests/fixture/issues/8919/input.js
new file mode 100644
index 000000000000..ca6d306f5b59
--- /dev/null
+++ b/crates/swc_ecma_minifier/tests/fixture/issues/8919/input.js
@@ -0,0 +1,11 @@
+"use strict";
+const k = (() => {
+    switch ("") {
+        default:
+            var x;
+        case "":
+            x;
+    }
+    return x;
+})();
+console.log(k);
diff --git a/crates/swc_ecma_minifier/tests/fixture/issues/8919/output.js b/crates/swc_ecma_minifier/tests/fixture/issues/8919/output.js
new file mode 100644
index 000000000000..53588984737d
--- /dev/null
+++ b/crates/swc_ecma_minifier/tests/fixture/issues/8919/output.js
@@ -0,0 +1,2 @@
+"use strict";
+console.log(void 0);