parser: fix error for match sumtype with fntype (#15620)

vlib/v/parser/if_match.v

@@ -237,7 +237,8 @@ fn (mut p Parser) match_expr() ast.MatchExpr {
 		} else if (p.tok.kind == .name && !(p.tok.lit == 'C' && p.peek_tok.kind == .dot)
 			&& (((ast.builtin_type_names_matcher.matches(p.tok.lit) || p.tok.lit[0].is_capital())
 			&& p.peek_tok.kind != .lpar) || (p.peek_tok.kind == .dot && p.peek_token(2).lit.len > 0
-			&& p.peek_token(2).lit[0].is_capital()))) || p.is_only_array_type() {
+			&& p.peek_token(2).lit[0].is_capital()))) || p.is_only_array_type()
+			|| p.tok.lit == 'fn' {
 			mut types := []ast.Type{}
 			for {
 				// Sum type match

vlib/v/tests/inout/sumtype_with_fntype.out

@@ -2,5 +2,7 @@ Fn(fn () int)
 Fn(fn (int) int)
 123
 123
+123
+321
 321
 321

vlib/v/tests/inout/sumtype_with_fntype.vv

@@ -23,10 +23,24 @@ fn main() {
 		println(x1())
 	}
 
+	match x1 {
+		fn () int {
+			println(x1())
+		}
+		else {}
+	}
+
 	x2 := abc(2)
 	y2 := x2 as fn (int) int
 	println(y2(321))
 	if x2 is fn (int) int {
 		println(x2(321))
 	}
+
+	match x2 {
+		fn (int) int {
+			println(x2(321))
+		}
+		else {}
+	}
 }