Just declare the variable instead of initializing it as well

regex/compile.go

@@ -498,7 +498,7 @@ func shuntingYard(re string, flags ...ReFlag) ([]postfixNode, error) {
 				}
 			} else if re_postfix[i] == 'p' || re_postfix[i] == 'P' {
 				charClassInverted := (re_postfix[i] == 'P')
-				charsInClass := []rune{}
+				var charsInClass []rune
 				i++
 				if isUnicodeCharClassLetter(re_postfix[i]) {
 					var err error
@@ -713,7 +713,7 @@ func shuntingYard(re string, flags ...ReFlag) ([]postfixNode, error) {
 						}
 					} else if re_postfix[i] == 'p' || re_postfix[i] == 'P' {
 						charClassInverted := (re_postfix[i] == 'P')
-						charsInList := []rune{}
+						var charsInList []rune
 						i++
 						if isUnicodeCharClassLetter(re_postfix[i]) {
 							var err error