Reverse the order in which I pop states for alternation, because this messes with the left branch-right branch thing

regex/compile.go

@@ -1059,8 +1059,8 @@ func thompson(re []postfixNode) (Reg, error) {
 			// 	'|a'
 			// 	'^a|'
 			// 	'^|a'
-			s1, err1 := pop(&nfa)
-			s2, err2 := pop(&nfa)
+			s2, err1 := pop(&nfa)
+			s1, err2 := pop(&nfa)
 			if err2 != nil || (s2.groupBegin && len(s2.transitions) == 0) { // Doesn't exist, or its just an LPAREN
 				if err2 == nil { // Roundabout way of saying that this node existed, but it was an LPAREN, so we append it back
 					nfa = append(nfa, s2)