parser: fix optional fn argument (#15271)

Author: yuyi98

vlib/v/parser/parse_type.v

@@ -379,7 +379,7 @@ pub fn (mut p Parser) parse_type() ast.Type {
 		p.next()
 		is_result = true
 	}
-	if (is_optional || is_result) && p.tok.line_nr > line_nr {
+	if (is_optional || is_result) && (p.tok.line_nr > line_nr || p.tok.kind in [.comma, .rpar]) {
 		mut typ := ast.void_type
 		if is_optional {
 			typ = typ.set_flag(.optional)

vlib/v/tests/inout/optional_fn_arg.out

@@ -0,0 +1 @@
+test

vlib/v/tests/inout/optional_fn_arg.vv

@@ -0,0 +1,16 @@
+module main
+
+fn test(f fn () ?) ? {
+	return error('test')
+}
+
+fn test1() ? {
+	return error('test1')
+}
+
+fn main() {
+	test(test1) or {
+		println(err)
+		return
+	}
+}