From bccb1c3bd9155e1045e2fcac7dff2245250f7bcb Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Mon, 10 Oct 2022 01:02:23 +0100
Subject: [PATCH] fix corner case in `unused` (#5706)

fixes #5705
---
 lib/compress.js               |  7 +++----
 test/compress/rests.js        | 18 ++++++++++++++++++
 test/compress/side_effects.js |  4 +---
 3 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index 26daf3e2aa..58f083226d 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -7251,15 +7251,13 @@ Compressor.prototype.compress = function(node) {
                 node.name = null;
             }
             if (node instanceof AST_Lambda) {
+                descend_scope();
                 if (drop_funcs && node !== self && node instanceof AST_LambdaDefinition) {
                     var def = node.name.definition();
                     if (!(def.id in in_use_ids)) {
                         log(node.name, "Dropping unused function {name}");
                         def.eliminated++;
-                        if (parent instanceof AST_ExportDefault) {
-                            descend_scope();
-                            return to_func_expr(node, true);
-                        }
+                        if (parent instanceof AST_ExportDefault) return to_func_expr(node, true);
                         return in_list ? List.skip : make_node(AST_EmptyStatement, node);
                     }
                 }
@@ -7357,6 +7355,7 @@ Compressor.prototype.compress = function(node) {
                     }
                     fns_with_marked_args.push(node);
                 }
+                return node;
             }
             if (node instanceof AST_Catch && node.argname instanceof AST_Destructured) {
                 node.argname.transform(trimmer);
diff --git a/test/compress/rests.js b/test/compress/rests.js
index b18ab0b457..4d020d23eb 100644
--- a/test/compress/rests.js
+++ b/test/compress/rests.js
@@ -1624,3 +1624,21 @@ issue_5552_4: {
     expect_stdout: "PASS"
     node_version: ">=6"
 }
+
+issue_5705: {
+    options = {
+        reduce_vars: true,
+        rests: true,
+        unused: true,
+    }
+    input: {
+        (function(...a) {
+            var b = { ...a };
+        })(console.log("PASS"));
+    }
+    expect: {
+        (function() {})(console.log("PASS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8.3.0"
+}
diff --git a/test/compress/side_effects.js b/test/compress/side_effects.js
index 090a656620..3c09448d08 100644
--- a/test/compress/side_effects.js
+++ b/test/compress/side_effects.js
@@ -584,9 +584,7 @@ issue_4668: {
     }
     expect: {
         console.log(function f() {
-            (function g() {
-                0;
-            })();
+            (function g() {})();
         }());
     }
     expect_stdout: "undefined"