Function impl_subject_and_oblig

pub(crate) fn impl_subject_and_oblig<'a, 'tcx>(
    selcx: &SelectionContext<'a, 'tcx>,
    param_env: ParamEnv<'tcx>,
    impl_def_id: DefId,
    impl_args: GenericArgsRef<'tcx>,
    cause: impl Fn(usize, Span) -> ObligationCause<'tcx>,
) -> (ImplSubject<'tcx>, impl Iterator<Item = PredicateObligation<'tcx>>)

Instantiate all bound parameters of the impl subject with the given args, returning the resulting subject and all obligations that arise. The obligations are closed under normalization.