let FIXME refer to tracking issue

Author: RalfJung

src/libcore/fmt/float.rs

@@ -22,7 +22,7 @@ fn float_to_decimal_common_exact<T>(fmt: &mut Formatter, num: &T,
     unsafe {
         let mut buf = MaybeUninit::<[u8; 1024]>::uninitialized(); // enough for f32 and f64
         let mut parts = MaybeUninit::<[flt2dec::Part; 4]>::uninitialized();
-        // FIXME: Technically, this is calling `get_mut` on an uninitialized
+        // FIXME(#53491): Technically, this is calling `get_mut` on an uninitialized
         // `MaybeUninit` (here and elsewhere in this file).  Revisit this once
         // we decided whether that is valid or not.
         let formatted = flt2dec::to_exact_fixed_str(flt2dec::strategy::grisu::format_exact,

src/libcore/mem.rs

@@ -1118,7 +1118,7 @@ impl<T> MaybeUninit<T> {
     ///
     /// It is up to the caller to guarantee that the `MaybeUninit` really is in an initialized
     /// state, otherwise this will immediately cause undefined behavior.
-    // FIXME: We currently rely on the above being incorrect, i.e., we have references
+    // FIXME(#53491): We currently rely on the above being incorrect, i.e., we have references
     // to uninitialized data (e.g. in `libcore/fmt/float.rs`).  We should make
     // a final decision about the rules before stabilization.
     #[unstable(feature = "maybe_uninit", issue = "53491")]