Function resolve_projection_from_struct_ident 

fn resolve_projection_from_struct_ident<'tcx>(
    tcx: TyCtxt<'tcx>,
    def_id: DefId,
    base_ident: String,
    fields: Vec<String>,
    struct_ty: Ty<'tcx>,
) -> Option<(usize, Vec<(usize, Ty<'tcx>)>, Ty<'tcx>)>