Add tracking issue

Author: varkor

Diff for: src/libcore/bool.rs

@@ -13,7 +13,7 @@ impl bool {
     /// assert_eq!(false.then(0), None);
     /// assert_eq!(true.then(0), Some(0));
     /// ```
-    #[unstable(feature = "bool_to_option", issue = "0")]
+    #[unstable(feature = "bool_to_option", issue = "64260")]
     #[inline]
     pub fn then<T>(self, t: T) -> Option<T> {
         if self {
@@ -33,7 +33,7 @@ impl bool {
     /// assert_eq!(false.then_with(|| 0), None);
     /// assert_eq!(true.then_with(|| 0), Some(0));
     /// ```
-    #[unstable(feature = "bool_to_option", issue = "0")]
+    #[unstable(feature = "bool_to_option", issue = "64260")]
     #[inline]
     pub fn then_with<T, F: FnOnce() -> T>(self, f: F) -> Option<T> {
         if self {