rustdoc: don't ICE on TyKind::Typeof

Author: WaffleLapkin

src/librustdoc/clean/mod.rs

@@ -1543,8 +1543,7 @@ pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> T
         }
         TyKind::BareFn(barefn) => BareFunction(Box::new(clean_bare_fn_ty(barefn, cx))),
         // Rustdoc handles `TyKind::Err`s by turning them into `Type::Infer`s.
-        TyKind::Infer | TyKind::Err => Infer,
-        TyKind::Typeof(..) => panic!("unimplemented type {:?}", ty.kind),
+        TyKind::Infer | TyKind::Err | TyKind::Typeof(..) => Infer,
     }
 }