patch 8.2.1308: Vim9: accidentally using "x" causes Vim to exit Commit: https://github.com/vim/vim/commit/ae616494d77e9930da703d65d12ac0abf6dc425f Author: Bram Moolenaar <Bram@vim.org> Date: Tue Jul 28 20:07:27 2020 +0200 patch 8.2.1308: Vim9: accidentally using "x" causes Vim to exit Problem: Vim9: accidentally using "x" causes Vim to exit. Solution: Disallow using ":x" or "xit" in Vim9 script. (closes https://github.com/vim/vim/issues/6399)

--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -7409,6 +7409,13 @@ compile_def_function(ufunc_T *ufunc, int
 
 	    // TODO: other commands with an expression argument
 
+	    case CMD_append:
+	    case CMD_change:
+	    case CMD_insert:
+	    case CMD_xit:
+		    not_in_vim9(&ea);
+		    goto erret;
+
 	    case CMD_SIZE:
 		    semsg(_("E476: Invalid command: %s"), ea.cmd);
 		    goto erret;