From 342c320bfa1f43f25262c0ba403a51df8228c655 Mon Sep 17 00:00:00 2001
From: magic-akari <akari.ccino@gmail.com>
Date: Sun, 13 Feb 2022 03:34:06 +0800
Subject: [PATCH] fix(es/compat): Fix destructing of `const` (#3545)

---
 .../src/es2015/destructuring.rs               | 12 ++++++++++
 .../tests/es2015_destructuring.rs             | 22 +++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/crates/swc_ecma_transforms_compat/src/es2015/destructuring.rs b/crates/swc_ecma_transforms_compat/src/es2015/destructuring.rs
index 61642d61e85..6b9bd21d9ed 100644
--- a/crates/swc_ecma_transforms_compat/src/es2015/destructuring.rs
+++ b/crates/swc_ecma_transforms_compat/src/es2015/destructuring.rs
@@ -960,6 +960,18 @@ impl VisitMut for AssignFolder {
 
         *declarators = decls;
     }
+
+    fn visit_mut_var_decl(&mut self, var_decl: &mut VarDecl) {
+        var_decl.decls.visit_mut_with(self);
+
+        if var_decl.kind == VarDeclKind::Const {
+            var_decl.decls.iter_mut().for_each(|v| {
+                if v.init.is_none() {
+                    v.init = Some(undefined(DUMMY_SP));
+                }
+            })
+        }
+    }
 }
 
 impl Destructuring {
diff --git a/crates/swc_ecma_transforms_compat/tests/es2015_destructuring.rs b/crates/swc_ecma_transforms_compat/tests/es2015_destructuring.rs
index 5830616710f..5ae8d627437 100644
--- a/crates/swc_ecma_transforms_compat/tests/es2015_destructuring.rs
+++ b/crates/swc_ecma_transforms_compat/tests/es2015_destructuring.rs
@@ -2103,3 +2103,25 @@ test!(
     assert.sameValue(iterCount, 1, 'Iteration occurred as expected');
    "
 );
+
+test!(
+    syntax(),
+    |_| tr(),
+    statements_const_id_init_hole,
+    "\
+    const [x] = [,];
+    const [y] = [,], [z] = [,]
+    ",
+    "\
+    const x = void 0;
+    const y = void 0, z = void 0;
+    "
+);
+
+test!(
+    syntax(),
+    |_| tr(),
+    statements_let_id_init_hole,
+    "let [x] = [,];",
+    "let x;"
+);