fix

vlib/v/checker/checker.v

@@ -553,6 +553,9 @@ fn (mut c Checker) fn_type_decl(node ast.FnTypeDecl) {
 	if ret_sym.kind == .placeholder {
 		c.error('unknown type `${ret_sym.name}`', fn_info.return_type_pos)
 	}
+	if !node.typ.has_flag(.option) {
+		c.warn('you should declare it as Option instead', node.type_pos)
+	}
 	for arg in fn_info.params {
 		c.ensure_type_exists(arg.typ, arg.type_pos) or { return }
 		arg_sym := c.table.sym(arg.typ)

vlib/v/checker/struct.v

@@ -137,9 +137,13 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 			}
 			if sym.kind == .function {
 				fn_info := sym.info as ast.FnType
-				if !field.typ.has_flag(.option) && fn_info.is_anon {
-					c.warn('direct function declaration is not recommended, use Option instead (?fn ...)',
-						field.type_pos)
+				if !field.typ.has_flag(.option) {
+					if fn_info.is_anon {
+						c.warn('you should declare it as Option instead (?fn ...)', field.type_pos)
+					} else {
+						c.warn('this is not recommended, you should use Option function instead',
+							field.type_pos)
+					}
 				}
 			}