message: Make BoundRegion have a kind of BoungRegionKind
diff: @@ -64,7 +64,7 @@ pub(crate) fn fn_sig_for_fn_abi<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx
  ty::Generator(_, substs, _) => {
  let sig = substs.as_generator().poly_sig();
  - let env_region = ty::ReLateBound(ty::INNERMOST, ty::BrEnv);
  + let env_region = ty::ReLateBound(ty::INNERMOST, ty::BoundRegion { kind: ty::BrEnv });
  let env_ty = tcx.mk_mut_ref(tcx.mk_region(env_region), ty);
  let pin_did = tcx.require_lang_item(rustc_hir::LangItem::Pin, None);
  