Add unstable attribute to `char::from_u32_unchecked`

src/libcore/char.rs

@@ -91,6 +91,7 @@ pub fn from_u32(i: u32) -> Option<char> {
 /// Converts a `u32` to an `char`, not checking whether it is a valid unicode
 /// codepoint.
 #[inline]
+#[unstable(feature = "char_from_unchecked", reason = "recently added API")]
 pub unsafe fn from_u32_unchecked(i: u32) -> char {
     transmute(i)
 }

src/libstd/lib.rs

@@ -209,6 +209,7 @@
 #![feature(borrow_state)]
 #![feature(box_raw)]
 #![feature(box_syntax)]
+#![feature(char_from_unchecked)]
 #![feature(char_internals)]
 #![feature(clone_from_slice)]
 #![feature(collections)]