compiler/rustc_borrowck/src/type_check/canonical.rs

   1 use std::fmt;
   2
   3 use rustc_infer::infer::canonical::Canonical;
   4 use rustc_infer::traits::query::NoSolution;
   5 use rustc_middle::mir::ConstraintCategory;
   6 use rustc_middle::ty::{self, ToPredicate, TypeFoldable};
   7 use rustc_span::def_id::DefId;
   8 use rustc_span::Span;
   9 use rustc_trait_selection::traits::query::type_op::{self, TypeOpOutput};
  10 use rustc_trait_selection::traits::query::Fallible;
  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, category, op), level = "trace")]
  28     pub(super) fn fully_perform_op<R, 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         if let Some(data) = constraints {
  43             self.push_region_constraints(locations, category, data);
  44         }
  45
  46         let universe = self.infcx.universe();
  47
  48         if old_universe != universe {
  49             let universe_info = match error_info {
  50                 Some(error_info) => error_info.to_universe_info(old_universe),
  51                 None => UniverseInfo::other(),
  52             };
  53             for u in old_universe..universe {
  54                 self.borrowck_context
  55                     .constraints
  56                     .universe_causes
  57                     .insert(u + 1, universe_info.clone());
  58             }
  59         }
  60
  61         Ok(output)
  62     }
  63
  64     pub(super) fn instantiate_canonical_with_fresh_inference_vars<T>(
  65         &mut self,
  66         span: Span,
  67         canonical: &Canonical<'tcx, T>,
  68     ) -> T
  69     where
  70         T: TypeFoldable<'tcx>,
  71     {
  72         let (instantiated, _) =
  73             self.infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
  74
  75         for u in 0..canonical.max_universe.as_u32() {
  76             let info = UniverseInfo::other();
  77             self.borrowck_context
  78                 .constraints
  79                 .universe_causes
  80                 .insert(ty::UniverseIndex::from_u32(u), info);
  81         }
  82
  83         instantiated
  84     }
  85
  86     #[instrument(skip(self), level = "debug")]
  87     pub(super) fn prove_trait_ref(
  88         &mut self,
  89         trait_ref: ty::TraitRef<'tcx>,
  90         locations: Locations,
  91         category: ConstraintCategory<'tcx>,
  92     ) {
  93         self.prove_predicates(
  94             Some(ty::Binder::dummy(ty::PredicateKind::Trait(ty::TraitPredicate {
  95                 trait_ref,
  96                 constness: ty::BoundConstness::NotConst,
  97                 polarity: ty::ImplPolarity::Positive,
  98             }))),
  99             locations,
 100             category,
 101         );
 102     }
 103
 104     pub(super) fn normalize_and_prove_instantiated_predicates(
 105         &mut self,
 106         // Keep this parameter for now, in case we start using
 107         // it in `ConstraintCategory` at some point.
 108         _def_id: DefId,
 109         instantiated_predicates: ty::InstantiatedPredicates<'tcx>,
 110         locations: Locations,
 111     ) {
 112         for (predicate, span) in instantiated_predicates
 113             .predicates
 114             .into_iter()
 115             .zip(instantiated_predicates.spans.into_iter())
 116         {
 117             debug!(?predicate);
 118             let predicate = self.normalize(predicate, locations);
 119             self.prove_predicate(predicate, locations, ConstraintCategory::Predicate(span));
 120         }
 121     }
 122
 123     pub(super) fn prove_predicates(
 124         &mut self,
 125         predicates: impl IntoIterator<Item = impl ToPredicate<'tcx>>,
 126         locations: Locations,
 127         category: ConstraintCategory<'tcx>,
 128     ) {
 129         for predicate in predicates {
 130             let predicate = predicate.to_predicate(self.tcx());
 131             debug!("prove_predicates(predicate={:?}, locations={:?})", predicate, locations,);
 132
 133             self.prove_predicate(predicate, locations, category);
 134         }
 135     }
 136
 137     #[instrument(skip(self), level = "debug")]
 138     pub(super) fn prove_predicate(
 139         &mut self,
 140         predicate: ty::Predicate<'tcx>,
 141         locations: Locations,
 142         category: ConstraintCategory<'tcx>,
 143     ) {
 144         let param_env = self.param_env;
 145         self.fully_perform_op(
 146             locations,
 147             category,
 148             param_env.and(type_op::prove_predicate::ProvePredicate::new(predicate)),
 149         )
 150         .unwrap_or_else(|NoSolution| {
 151             span_mirbug!(self, NoSolution, "could not prove {:?}", predicate);
 152         })
 153     }
 154
 155     #[instrument(skip(self), level = "debug")]
 156     pub(super) fn normalize<T>(&mut self, value: T, location: impl NormalizeLocation) -> T
 157     where
 158         T: type_op::normalize::Normalizable<'tcx> + fmt::Display + Copy + 'tcx,
 159     {
 160         let param_env = self.param_env;
 161         self.fully_perform_op(
 162             location.to_locations(),
 163             ConstraintCategory::Boring,
 164             param_env.and(type_op::normalize::Normalize::new(value)),
 165         )
 166         .unwrap_or_else(|NoSolution| {
 167             span_mirbug!(self, NoSolution, "failed to normalize `{:?}`", value);
 168             value
 169         })
 170     }
 171 }