patch 9.0.1559: function argument types not always checked Commit: https://github.com/vim/vim/commit/2ba51236fb7c27fe16dad4c44242f00e17c19726 Author: Bram Moolenaar <Bram@vim.org> Date: Mon May 15 16:22:38 2023 +0100 patch 9.0.1559: function argument types not always checked Problem: Function argument types not always checked and using v:none may cause an error. Solution: Check argument types once the function type is known. Do not give an error for using v:none as an argument. (closes #12200)

--- a/src/vim9type.c
+++ b/src/vim9type.c
@@ -970,7 +970,10 @@ check_argument_types(
 	}
 	else
 	    expected = type->tt_args[i];
-	if (check_typval_arg_type(expected, tv, NULL, i + 1) == FAIL)
+
+	// check the type, unless the value is v:none
+	if ((tv->v_type != VAR_SPECIAL || tv->vval.v_number != VVAL_NONE)
+		   && check_typval_arg_type(expected, tv, NULL, i + 1) == FAIL)
 	    return FAIL;
     }
     return OK;