Function rustc_typeck::coherence::enforce_empty_impls_for_marker_traits

pub(in coherence) fn enforce_empty_impls_for_marker_traits(
    tcx: TyCtxt<'_>, 
    impl_def_id: LocalDefId, 
    trait_def_id: DefId
)

We allow impls of marker traits to overlap, so they can't override impls as that could make it ambiguous which associated item to use.