| use rustc_hir::lang_items::LangItem; |
| use rustc_middle::query::Providers; |
| use rustc_middle::ty::{self, Ty, TyCtxt}; |
| |
| use rustc_infer::infer::TyCtxtInferExt; |
| use rustc_trait_selection::traits::{ObligationCause, ObligationCtxt}; |
| |
| /// This method returns true if and only if `adt_ty` itself has been marked as |
| /// eligible for structural-match: namely, if it implements |
| /// `StructuralPartialEq` (which is injected by `#[derive(PartialEq)]`). |
| /// |
| /// Note that this does *not* recursively check if the substructure of `adt_ty` |
| /// implements the trait. |
| fn has_structural_eq_impl<'tcx>(tcx: TyCtxt<'tcx>, adt_ty: Ty<'tcx>) -> bool { |
| let infcx = &tcx.infer_ctxt().build(); |
| let cause = ObligationCause::dummy(); |
| |
| let ocx = ObligationCtxt::new(infcx); |
| // require `#[derive(PartialEq)]` |
| let structural_peq_def_id = |
| infcx.tcx.require_lang_item(LangItem::StructuralPeq, Some(cause.span)); |
| ocx.register_bound(cause.clone(), ty::ParamEnv::empty(), adt_ty, structural_peq_def_id); |
| |
| // We deliberately skip *reporting* fulfillment errors (via |
| // `report_fulfillment_errors`), for two reasons: |
| // |
| // 1. The error messages would mention `std::marker::StructuralPartialEq` |
| // (a trait which is solely meant as an implementation detail |
| // for now), and |
| // |
| // 2. We are sometimes doing future-incompatibility lints for |
| // now, so we do not want unconditional errors here. |
| ocx.select_all_or_error().is_empty() |
| } |
| |
| pub(crate) fn provide(providers: &mut Providers) { |
| providers.has_structural_eq_impl = has_structural_eq_impl; |
| } |