compiler/rustc_infer/src/traits/engine.rs

   1 use crate::infer::InferCtxt;
   2 use crate::traits::Obligation;
   3 use rustc_hir::def_id::DefId;
   4 use rustc_middle::ty::{self, ToPredicate, Ty};
   5
   6 use super::FulfillmentError;
   7 use super::{ObligationCause, PredicateObligation};
   8
   9 pub trait TraitEngine<'tcx>: 'tcx {
  10     /// Requires that `ty` must implement the trait with `def_id` in
  11     /// the given environment. This trait must not have any type
  12     /// parameters (except for `Self`).
  13     fn register_bound(
  14         &mut self,
  15         infcx: &InferCtxt<'tcx>,
  16         param_env: ty::ParamEnv<'tcx>,
  17         ty: Ty<'tcx>,
  18         def_id: DefId,
  19         cause: ObligationCause<'tcx>,
  20     ) {
  21         let trait_ref = infcx.tcx.mk_trait_ref(def_id, [ty]);
  22         self.register_predicate_obligation(
  23             infcx,
  24             Obligation {
  25                 cause,
  26                 recursion_depth: 0,
  27                 param_env,
  28                 predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(infcx.tcx),
  29             },
  30         );
  31     }
  32
  33     fn register_predicate_obligation(
  34         &mut self,
  35         infcx: &InferCtxt<'tcx>,
  36         obligation: PredicateObligation<'tcx>,
  37     );
  38
  39     fn select_where_possible(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
  40
  41     fn collect_remaining_errors(&mut self) -> Vec<FulfillmentError<'tcx>>;
  42
  43     fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>;
  44
  45     /// Among all pending obligations, collect those are stalled on a inference variable which has
  46     /// changed since the last call to `select_where_possible`. Those obligations are marked as
  47     /// successful and returned.
  48     fn drain_unstalled_obligations(
  49         &mut self,
  50         infcx: &InferCtxt<'tcx>,
  51     ) -> Vec<PredicateObligation<'tcx>>;
  52 }
  53
  54 pub trait TraitEngineExt<'tcx> {
  55     fn register_predicate_obligations(
  56         &mut self,
  57         infcx: &InferCtxt<'tcx>,
  58         obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>,
  59     );
  60
  61     fn select_all_or_error(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
  62 }
  63
  64 impl<'tcx, T: ?Sized + TraitEngine<'tcx>> TraitEngineExt<'tcx> for T {
  65     fn register_predicate_obligations(
  66         &mut self,
  67         infcx: &InferCtxt<'tcx>,
  68         obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>,
  69     ) {
  70         for obligation in obligations {
  71             self.register_predicate_obligation(infcx, obligation);
  72         }
  73     }
  74
  75     fn select_all_or_error(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>> {
  76         let errors = self.select_where_possible(infcx);
  77         if !errors.is_empty() {
  78             return errors;
  79         }
  80
  81         self.collect_remaining_errors()
  82     }
  83 }