compiler/rustc_borrowck/src/type_check/canonical.rs

   1 use std::fmt;
   2
   3 use rustc_infer::infer::{canonical::Canonical, InferOk};
   4 use rustc_middle::mir::ConstraintCategory;
   5 use rustc_middle::ty::{self, ToPredicate, Ty, TypeFoldable};
   6 use rustc_span::def_id::DefId;
   7 use rustc_span::Span;
   8 use rustc_trait_selection::traits::query::type_op::{self, TypeOpOutput};
   9 use rustc_trait_selection::traits::query::{Fallible, NoSolution};
  10 use rustc_trait_selection::traits::{ObligationCause, ObligationCtxt};
  11
  12 use crate::diagnostics::{ToUniverseInfo, UniverseInfo};
  13
  14 use super::{Locations, NormalizeLocation, TypeChecker};
  15
  16 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
  17     /// Given some operation `op` that manipulates types, proves
  18     /// predicates, or otherwise uses the inference context, executes
  19     /// `op` and then executes all the further obligations that `op`
  20     /// returns. This will yield a set of outlives constraints amongst
  21     /// regions which are extracted and stored as having occurred at
  22     /// `locations`.
  23     ///
  24     /// **Any `rustc_infer::infer` operations that might generate region
  25     /// constraints should occur within this method so that those
  26     /// constraints can be properly localized!**
  27     #[instrument(skip(self, op), level = "trace")]
  28     pub(super) fn fully_perform_op<R: fmt::Debug, Op>(
  29         &mut self,
  30         locations: Locations,
  31         category: ConstraintCategory<'tcx>,
  32         op: Op,
  33     ) -> Fallible<R>
  34     where
  35         Op: type_op::TypeOp<'tcx, Output = R>,
  36         Op::ErrorInfo: ToUniverseInfo<'tcx>,
  37     {
  38         let old_universe = self.infcx.universe();
  39
  40         let TypeOpOutput { output, constraints, error_info } = op.fully_perform(self.infcx)?;
  41
  42         debug!(?output, ?constraints);
  43
  44         if let Some(data) = constraints {
  45             self.push_region_constraints(locations, category, data);
  46         }
  47
  48         let universe = self.infcx.universe();
  49
  50         if old_universe != universe {
  51             let universe_info = match error_info {
  52                 Some(error_info) => error_info.to_universe_info(old_universe),
  53                 None => UniverseInfo::other(),
  54             };
  55             for u in (old_universe + 1)..=universe {
  56                 self.borrowck_context.constraints.universe_causes.insert(u, universe_info.clone());
  57             }
  58         }
  59
  60         Ok(output)
  61     }
  62
  63     pub(super) fn instantiate_canonical_with_fresh_inference_vars<T>(
  64         &mut self,
  65         span: Span,
  66         canonical: &Canonical<'tcx, T>,
  67     ) -> T
  68     where
  69         T: TypeFoldable<'tcx>,
  70     {
  71         let old_universe = self.infcx.universe();
  72
  73         let (instantiated, _) =
  74             self.infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
  75
  76         for u in (old_universe + 1)..=self.infcx.universe() {
  77             self.borrowck_context.constraints.universe_causes.insert(u, UniverseInfo::other());
  78         }
  79
  80         instantiated
  81     }
  82
  83     #[instrument(skip(self), level = "debug")]
  84     pub(super) fn prove_trait_ref(
  85         &mut self,
  86         trait_ref: ty::TraitRef<'tcx>,
  87         locations: Locations,
  88         category: ConstraintCategory<'tcx>,
  89     ) {
  90         self.prove_predicate(
  91             ty::Binder::dummy(ty::PredicateKind::Clause(ty::Clause::Trait(ty::TraitPredicate {
  92                 trait_ref,
  93                 constness: ty::BoundConstness::NotConst,
  94                 polarity: ty::ImplPolarity::Positive,
  95             }))),
  96             locations,
  97             category,
  98         );
  99     }
 100
 101     #[instrument(level = "debug", skip(self))]
 102     pub(super) fn normalize_and_prove_instantiated_predicates(
 103         &mut self,
 104         // Keep this parameter for now, in case we start using
 105         // it in `ConstraintCategory` at some point.
 106         _def_id: DefId,
 107         instantiated_predicates: ty::InstantiatedPredicates<'tcx>,
 108         locations: Locations,
 109     ) {
 110         for (predicate, span) in instantiated_predicates {
 111             debug!(?predicate);
 112             let category = ConstraintCategory::Predicate(span);
 113             let predicate = self.normalize_with_category(predicate, locations, category);
 114             self.prove_predicate(predicate, locations, category);
 115         }
 116     }
 117
 118     pub(super) fn prove_predicates(
 119         &mut self,
 120         predicates: impl IntoIterator<Item = impl ToPredicate<'tcx> + std::fmt::Debug>,
 121         locations: Locations,
 122         category: ConstraintCategory<'tcx>,
 123     ) {
 124         for predicate in predicates {
 125             self.prove_predicate(predicate, locations, category);
 126         }
 127     }
 128
 129     #[instrument(skip(self), level = "debug")]
 130     pub(super) fn prove_predicate(
 131         &mut self,
 132         predicate: impl ToPredicate<'tcx> + std::fmt::Debug,
 133         locations: Locations,
 134         category: ConstraintCategory<'tcx>,
 135     ) {
 136         let param_env = self.param_env;
 137         let predicate = predicate.to_predicate(self.tcx());
 138         self.fully_perform_op(
 139             locations,
 140             category,
 141             param_env.and(type_op::prove_predicate::ProvePredicate::new(predicate)),
 142         )
 143         .unwrap_or_else(|NoSolution| {
 144             span_mirbug!(self, NoSolution, "could not prove {:?}", predicate);
 145         })
 146     }
 147
 148     pub(super) fn normalize<T>(&mut self, value: T, location: impl NormalizeLocation) -> T
 149     where
 150         T: type_op::normalize::Normalizable<'tcx> + fmt::Display + Copy + 'tcx,
 151     {
 152         self.normalize_with_category(value, location, ConstraintCategory::Boring)
 153     }
 154
 155     #[instrument(skip(self), level = "debug")]
 156     pub(super) fn normalize_with_category<T>(
 157         &mut self,
 158         value: T,
 159         location: impl NormalizeLocation,
 160         category: ConstraintCategory<'tcx>,
 161     ) -> T
 162     where
 163         T: type_op::normalize::Normalizable<'tcx> + fmt::Display + Copy + 'tcx,
 164     {
 165         let param_env = self.param_env;
 166         self.fully_perform_op(
 167             location.to_locations(),
 168             category,
 169             param_env.and(type_op::normalize::Normalize::new(value)),
 170         )
 171         .unwrap_or_else(|NoSolution| {
 172             span_mirbug!(self, NoSolution, "failed to normalize `{:?}`", value);
 173             value
 174         })
 175     }
 176
 177     #[instrument(skip(self), level = "debug")]
 178     pub(super) fn ascribe_user_type(
 179         &mut self,
 180         mir_ty: Ty<'tcx>,
 181         user_ty: ty::UserType<'tcx>,
 182         span: Span,
 183     ) {
 184         self.fully_perform_op(
 185             Locations::All(span),
 186             ConstraintCategory::Boring,
 187             self.param_env.and(type_op::ascribe_user_type::AscribeUserType::new(mir_ty, user_ty)),
 188         )
 189         .unwrap_or_else(|err| {
 190             span_mirbug!(
 191                 self,
 192                 span,
 193                 "ascribe_user_type `{mir_ty:?}=={user_ty:?}` failed with `{err:?}`",
 194             );
 195         });
 196     }
 197
 198     /// *Incorrectly* skips the WF checks we normally do in `ascribe_user_type`.
 199     ///
 200     /// FIXME(#104478, #104477): This is a hack for backward-compatibility.
 201     #[instrument(skip(self), level = "debug")]
 202     pub(super) fn ascribe_user_type_skip_wf(
 203         &mut self,
 204         mir_ty: Ty<'tcx>,
 205         user_ty: ty::UserType<'tcx>,
 206         span: Span,
 207     ) {
 208         let ty::UserType::Ty(user_ty) = user_ty else { bug!() };
 209
 210         // A fast path for a common case with closure input/output types.
 211         if let ty::Infer(_) = user_ty.kind() {
 212             self.eq_types(user_ty, mir_ty, Locations::All(span), ConstraintCategory::Boring)
 213                 .unwrap();
 214             return;
 215         }
 216
 217         // FIXME: Ideally MIR types are normalized, but this is not always true.
 218         let mir_ty = self.normalize(mir_ty, Locations::All(span));
 219
 220         let cause = ObligationCause::dummy_with_span(span);
 221         let param_env = self.param_env;
 222         let op = |infcx: &'_ _| {
 223             let ocx = ObligationCtxt::new_in_snapshot(infcx);
 224             let user_ty = ocx.normalize(&cause, param_env, user_ty);
 225             ocx.eq(&cause, param_env, user_ty, mir_ty)?;
 226             if !ocx.select_all_or_error().is_empty() {
 227                 return Err(NoSolution);
 228             }
 229             Ok(InferOk { value: (), obligations: vec![] })
 230         };
 231
 232         self.fully_perform_op(
 233             Locations::All(span),
 234             ConstraintCategory::Boring,
 235             type_op::custom::CustomTypeOp::new(op, || "ascribe_user_type_skip_wf".to_string()),
 236         )
 237         .unwrap_or_else(|err| {
 238             span_mirbug!(
 239                 self,
 240                 span,
 241                 "ascribe_user_type_skip_wf `{mir_ty:?}=={user_ty:?}` failed with `{err:?}`",
 242             );
 243         });
 244     }
 245 }