From 883d25b27dc8027f6c9bc6485e5f25a14aaf7f8c Mon Sep 17 00:00:00 2001
From: Boshen <1430279+Boshen@users.noreply.github.com>
Date: Thu, 23 Jan 2025 13:30:40 +0000
Subject: [PATCH] fix(minifier): keep esm in dce (#8677)

fixes https://github.com/rolldown/rolldown/issues/3402
---
 crates/oxc_minifier/src/peephole/remove_dead_code.rs | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/crates/oxc_minifier/src/peephole/remove_dead_code.rs b/crates/oxc_minifier/src/peephole/remove_dead_code.rs
index e3cdbba8feba1..8f54eda42026b 100644
--- a/crates/oxc_minifier/src/peephole/remove_dead_code.rs
+++ b/crates/oxc_minifier/src/peephole/remove_dead_code.rs
@@ -113,8 +113,10 @@ impl<'a, 'b> PeepholeOptimizations {
             if i - 1 <= index {
                 return true;
             }
-            // keep function declaration
-            if matches!(s.as_declaration(), Some(Declaration::FunctionDeclaration(_))) {
+            // Keep module syntax and function declaration
+            if s.is_module_declaration()
+                || matches!(s.as_declaration(), Some(Declaration::FunctionDeclaration(_)))
+            {
                 return true;
             }
             false
@@ -812,4 +814,10 @@ mod test {
         test("!1", "");
         test("1", "");
     }
+
+    #[test]
+    fn keep_module_syntax() {
+        test_same("throw foo; export let bar");
+        test_same("throw foo; export default bar");
+    }
 }