fix corner case in `default_values` (#4497)

fixes #4496

1 files changed, 4 insertions, 4 deletions

diff --git a/lib/compress.js b/lib/compress.js
index d5c22063..538b906e 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -7692,7 +7692,9 @@ merge(Compressor.prototype, {
             return !(arg instanceof AST_Spread);
         })) return;
         var pos = 0, last = 0;
-        var drop_fargs = fn === exp && !fn.name && compressor.drop_fargs(fn, call) ? function(argname, arg) {
+        var is_iife = fn === exp && !fn.name;
+        var drop_defaults = is_iife && compressor.option("default_values");
+        var drop_fargs = is_iife && compressor.drop_fargs(fn, call) ? function(argname, arg) {
             if (!argname) return true;
             if (argname instanceof AST_DestructuredArray) {
                 return argname.elements.length == 0 && arg instanceof AST_Array;
@@ -7705,9 +7707,7 @@ merge(Compressor.prototype, {
         var side_effects = [];
         for (var i = 0; i < args.length; i++) {
             var argname = fn.argnames[i];
-            if (compressor.option("default_values")
-                && argname instanceof AST_DefaultValue
-                && args[i].is_defined(compressor)) {
+            if (drop_defaults && argname instanceof AST_DefaultValue && args[i].is_defined(compressor)) {
                 fn.argnames[i] = argname = argname.name;
             }
             if (!argname || "__unused" in argname) {