fix corner case in inline (#5253)

fixes #5251

lib/compress.js

@@ -12925,6 +12925,7 @@ Compressor.prototype.compress = function(node) {
             if (scope instanceof AST_Toplevel && fn.variables.size() > (arrow ? 0 : 1)) {
                 if (!compressor.toplevel.vars) return;
                 if (fn.functions.size() > 0 && !compressor.toplevel.funcs) return;
+                defined.set("arguments", true);
             }
             var async = is_async(fn);
             if (async && !(compressor.option("awaits") && is_async(scope))) return;

test/compress/arrows.js

@@ -906,3 +906,24 @@ issue_4772: {
     expect_stdout: "PASS"
     node_version: ">=4"
 }
+
+issue_5251: {
+    options = {
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        (() => {
+            while (console.log(arguments))
+                var arguments = "FAIL";
+        })();
+    }
+    expect: {
+        (() => {
+            while (console.log(arguments))
+                var arguments = "FAIL";
+        })();
+    }
+    expect_stdout: true
+    node_version: ">=4"
+}