Add note on nonzero-sized uninhabited types

Author: varkor

src/librustc/ty/sty.rs

@@ -1508,7 +1508,8 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
     /// conservative: for some types that are uninhabited we return `false`,
     /// but we only return `true` for types that are definitely uninhabited.
     /// `ty.conservative_is_uninhabited` implies that any value of type `ty`
-    /// will be `Abi::Uninhabited`.
+    /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
+    /// size, to account for partial initialisation. See #49298 for details.)
     pub fn conservative_is_uninhabited(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> bool {
         // FIXME(varkor): we can make this less conversative by substituting concrete
         // type arguments.