Function build_marker_trait_obligations 

fn build_marker_trait_obligations<'tcx>(
    tcx: TyCtxt<'tcx>,
    self_ty_def_id: Option<DefId>,
    trait_kind: MarkerTraitKind,
) -> Vec<Property<'tcx>>

Generate the type-level ensures obligations for a marker-trait impl from the bundled std-trait-ensures.json template, substituting ty:Self with the implementing type.