fix corner case in `arguments` (#4967)

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 08b0f0d1..4340c8cc 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -11543,15 +11543,15 @@ merge(Compressor.prototype, {
         }
         var parent = compressor.parent();
         var assigned = is_lhs(compressor.self(), parent);
-        var def, fn, fn_parent;
+        var def, fn, fn_parent, index;
         if (compressor.option("arguments")
             && expr instanceof AST_SymbolRef
             && is_arguments(def = expr.definition())
             && !expr.in_arg
             && prop instanceof AST_Number
+            && Math.floor(index = prop.value) == index
             && (fn = def.scope) === find_lambda()
             && fn.uses_arguments < (assigned ? 2 : 3)) {
-            var index = prop.value;
             if (parent instanceof AST_UnaryPrefix && parent.operator == "delete") {
                 if (!def.deleted) def.deleted = [];
                 def.deleted[index] = true;