Function resolve_primitive_inherent_assoc_item 

fn resolve_primitive_inherent_assoc_item<'tcx>(
    tcx: TyCtxt<'tcx>,
    prim_ty: PrimitiveType,
    ns: Namespace,
    item_ident: Ident,
) -> Vec<(Res, DefId)>

Given a primitive type, try to resolve an associated item.