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     pub(super) fn fully_perform_op<R, Op>(
  28         &mut self,
  29         locations: Locations,
  30         category: ConstraintCategory,
  31         op: Op,
  32     ) -> Fallible<R>
  33     where
  34         Op: type_op::TypeOp<'tcx, Output = R>,
  35         Canonical<'tcx, Op>: ToUniverseInfo<'tcx>,
  36     {
  37         let old_universe = self.infcx.universe();
  38
  39         let TypeOpOutput { output, constraints, canonicalized_query } =
  40             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 canonicalized_query {
  50                 Some(canonicalized_query) => canonicalized_query.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     pub(super) fn prove_trait_ref(
  87         &mut self,
  88         trait_ref: ty::TraitRef<'tcx>,
  89         locations: Locations,
  90         category: ConstraintCategory,
  91     ) {
  92         self.prove_predicates(
  93             Some(ty::Binder::dummy(ty::PredicateKind::Trait(ty::TraitPredicate {
  94                 trait_ref,
  95                 constness: ty::BoundConstness::NotConst,
  96             }))),
  97             locations,
  98             category,
  99         );
 100     }
 101
 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             .predicates
 112             .into_iter()
 113             .zip(instantiated_predicates.spans.into_iter())
 114         {
 115             let predicate = self.normalize(predicate, locations);
 116             self.prove_predicate(predicate, locations, ConstraintCategory::Predicate(span));
 117         }
 118     }
 119
 120     pub(super) fn prove_predicates(
 121         &mut self,
 122         predicates: impl IntoIterator<Item = impl ToPredicate<'tcx>>,
 123         locations: Locations,
 124         category: ConstraintCategory,
 125     ) {
 126         for predicate in predicates {
 127             let predicate = predicate.to_predicate(self.tcx());
 128             debug!("prove_predicates(predicate={:?}, locations={:?})", predicate, locations,);
 129
 130             self.prove_predicate(predicate, locations, category);
 131         }
 132     }
 133
 134     pub(super) fn prove_predicate(
 135         &mut self,
 136         predicate: ty::Predicate<'tcx>,
 137         locations: Locations,
 138         category: ConstraintCategory,
 139     ) {
 140         debug!("prove_predicate(predicate={:?}, location={:?})", predicate, locations,);
 141
 142         let param_env = self.param_env;
 143         self.fully_perform_op(
 144             locations,
 145             category,
 146             param_env.and(type_op::prove_predicate::ProvePredicate::new(predicate)),
 147         )
 148         .unwrap_or_else(|NoSolution| {
 149             span_mirbug!(self, NoSolution, "could not prove {:?}", predicate);
 150         })
 151     }
 152
 153     pub(super) fn normalize<T>(&mut self, value: T, location: impl NormalizeLocation) -> T
 154     where
 155         T: type_op::normalize::Normalizable<'tcx> + fmt::Display + Copy + 'tcx,
 156     {
 157         debug!("normalize(value={:?}, location={:?})", value, location);
 158         let param_env = self.param_env;
 159         self.fully_perform_op(
 160             location.to_locations(),
 161             ConstraintCategory::Boring,
 162             param_env.and(type_op::normalize::Normalize::new(value)),
 163         )
 164         .unwrap_or_else(|NoSolution| {
 165             span_mirbug!(self, NoSolution, "failed to normalize `{:?}`", value);
 166             value
 167         })
 168     }
 169 }