fix corner case in `merge_vars`

fixes #4139

1 files changed, 4 insertions, 6 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 82bbbf1b..30a82e35 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4408,12 +4408,9 @@ merge(Compressor.prototype, {
             if (node instanceof AST_Scope) {
                 push();
                 segment.block = node;
-                if (node instanceof AST_Lambda) {
-                    if (node.name) {
-                        if (node !== self) segment.loop = true;
-                        references[node.name.definition().id] = false;
-                    }
-                    references[node.variables.get("arguments").id] = false;
+                if (node instanceof AST_Lambda && node.name) {
+                    if (node !== self) segment.loop = true;
+                    references[node.name.definition().id] = false;
                 }
                 descend();
                 pop();
@@ -4533,6 +4530,7 @@ merge(Compressor.prototype, {
         }
 
         function mark(sym, read, write) {
+            if (sym.name == "arguments") return;
             var def = sym.definition();
             if (def.id in references) {
                 var refs = references[def.id];