add unstable attribute

diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index ad448af9af82a28d5ed2eae3d416e1530bd86e9f..71617347e4c8a577d01804334b2a685e53a417ad 100644 (file)
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -4796,6 +4796,10 @@ pub enum IntErrorKind {
 
 impl ParseIntError {
     /// Outputs the detailed cause of parsing an integer failing.
+    #[unstable(feature = "int_error_matching",
+               reason = "it can be useful to match errors when making error messages \
+                         for integer parsing",
+               issue = "22639")]
     pub fn kind(self) -> IntErrorKind {
         self.kind
     }