Function rustc_hir_analysis::check::wfcheck::check_type_defn

fn check_type_defn<'tcx, F>(
    tcx: TyCtxt<'tcx>,
    item: &Item<'tcx>,
    all_sized: bool,
    lookup_fields: F
)where
    F: FnMut(&WfCheckingCtxt<'_, 'tcx>) -> Vec<AdtVariant<'tcx>>,

In a type definition, we check that to ensure that the types of the fields are well-formed.