compiler/rustc_trait_selection/src/infer.rs

   1 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
   2 use crate::traits::{self, TraitEngine, TraitEngineExt};
   3
   4 use rustc_hir::def_id::DefId;
   5 use rustc_hir::lang_items::LangItem;
   6 use rustc_infer::traits::ObligationCause;
   7 use rustc_middle::arena::ArenaAllocatable;
   8 use rustc_middle::infer::canonical::{Canonical, CanonicalizedQueryResponse, QueryResponse};
   9 use rustc_middle::traits::query::Fallible;
  10 use rustc_middle::ty::subst::SubstsRef;
  11 use rustc_middle::ty::ToPredicate;
  12 use rustc_middle::ty::{self, Ty, TypeFoldable, TypeVisitable};
  13 use rustc_span::{Span, DUMMY_SP};
  14
  15 use std::fmt::Debug;
  16
  17 pub use rustc_infer::infer::*;
  18
  19 pub trait InferCtxtExt<'tcx> {
  20     fn type_is_copy_modulo_regions(
  21         &self,
  22         param_env: ty::ParamEnv<'tcx>,
  23         ty: Ty<'tcx>,
  24         span: Span,
  25     ) -> bool;
  26
  27     fn type_is_sized_modulo_regions(
  28         &self,
  29         param_env: ty::ParamEnv<'tcx>,
  30         ty: Ty<'tcx>,
  31         span: Span,
  32     ) -> bool;
  33
  34     fn partially_normalize_associated_types_in<T>(
  35         &self,
  36         cause: ObligationCause<'tcx>,
  37         param_env: ty::ParamEnv<'tcx>,
  38         value: T,
  39     ) -> InferOk<'tcx, T>
  40     where
  41         T: TypeFoldable<'tcx>;
  42
  43     /// Check whether a `ty` implements given trait(trait_def_id).
  44     /// The inputs are:
  45     ///
  46     /// - the def-id of the trait
  47     /// - the self type
  48     /// - the *other* type parameters of the trait, excluding the self-type
  49     /// - the parameter environment
  50     ///
  51     /// Invokes `evaluate_obligation`, so in the event that evaluating
  52     /// `Ty: Trait` causes overflow, EvaluatedToRecur (or EvaluatedToUnknown)
  53     /// will be returned.
  54     fn type_implements_trait(
  55         &self,
  56         trait_def_id: DefId,
  57         ty: Ty<'tcx>,
  58         params: SubstsRef<'tcx>,
  59         param_env: ty::ParamEnv<'tcx>,
  60     ) -> traits::EvaluationResult;
  61 }
  62 impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
  63     fn type_is_copy_modulo_regions(
  64         &self,
  65         param_env: ty::ParamEnv<'tcx>,
  66         ty: Ty<'tcx>,
  67         span: Span,
  68     ) -> bool {
  69         let ty = self.resolve_vars_if_possible(ty);
  70
  71         if !(param_env, ty).needs_infer() {
  72             return ty.is_copy_modulo_regions(self.tcx, param_env);
  73         }
  74
  75         let copy_def_id = self.tcx.require_lang_item(LangItem::Copy, None);
  76
  77         // This can get called from typeck (by euv), and `moves_by_default`
  78         // rightly refuses to work with inference variables, but
  79         // moves_by_default has a cache, which we want to use in other
  80         // cases.
  81         traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, copy_def_id, span)
  82     }
  83
  84     fn type_is_sized_modulo_regions(
  85         &self,
  86         param_env: ty::ParamEnv<'tcx>,
  87         ty: Ty<'tcx>,
  88         span: Span,
  89     ) -> bool {
  90         let lang_item = self.tcx.require_lang_item(LangItem::Sized, None);
  91         traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, lang_item, span)
  92     }
  93
  94     /// Normalizes associated types in `value`, potentially returning
  95     /// new obligations that must further be processed.
  96     fn partially_normalize_associated_types_in<T>(
  97         &self,
  98         cause: ObligationCause<'tcx>,
  99         param_env: ty::ParamEnv<'tcx>,
 100         value: T,
 101     ) -> InferOk<'tcx, T>
 102     where
 103         T: TypeFoldable<'tcx>,
 104     {
 105         debug!("partially_normalize_associated_types_in(value={:?})", value);
 106         let mut selcx = traits::SelectionContext::new(self);
 107         let traits::Normalized { value, obligations } =
 108             traits::normalize(&mut selcx, param_env, cause, value);
 109         debug!(
 110             "partially_normalize_associated_types_in: result={:?} predicates={:?}",
 111             value, obligations
 112         );
 113         InferOk { value, obligations }
 114     }
 115
 116     fn type_implements_trait(
 117         &self,
 118         trait_def_id: DefId,
 119         ty: Ty<'tcx>,
 120         params: SubstsRef<'tcx>,
 121         param_env: ty::ParamEnv<'tcx>,
 122     ) -> traits::EvaluationResult {
 123         debug!(
 124             "type_implements_trait: trait_def_id={:?}, type={:?}, params={:?}, param_env={:?}",
 125             trait_def_id, ty, params, param_env
 126         );
 127
 128         let trait_ref =
 129             ty::TraitRef { def_id: trait_def_id, substs: self.tcx.mk_substs_trait(ty, params) };
 130
 131         let obligation = traits::Obligation {
 132             cause: traits::ObligationCause::dummy(),
 133             param_env,
 134             recursion_depth: 0,
 135             predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(self.tcx),
 136         };
 137         self.evaluate_obligation(&obligation).unwrap_or(traits::EvaluationResult::EvaluatedToErr)
 138     }
 139 }
 140
 141 pub trait InferCtxtBuilderExt<'tcx> {
 142     fn enter_canonical_trait_query<K, R>(
 143         &mut self,
 144         canonical_key: &Canonical<'tcx, K>,
 145         operation: impl FnOnce(&InferCtxt<'tcx>, &mut dyn TraitEngine<'tcx>, K) -> Fallible<R>,
 146     ) -> Fallible<CanonicalizedQueryResponse<'tcx, R>>
 147     where
 148         K: TypeFoldable<'tcx>,
 149         R: Debug + TypeFoldable<'tcx>,
 150         Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>;
 151 }
 152
 153 impl<'tcx> InferCtxtBuilderExt<'tcx> for InferCtxtBuilder<'tcx> {
 154     /// The "main method" for a canonicalized trait query. Given the
 155     /// canonical key `canonical_key`, this method will create a new
 156     /// inference context, instantiate the key, and run your operation
 157     /// `op`. The operation should yield up a result (of type `R`) as
 158     /// well as a set of trait obligations that must be fully
 159     /// satisfied. These obligations will be processed and the
 160     /// canonical result created.
 161     ///
 162     /// Returns `NoSolution` in the event of any error.
 163     ///
 164     /// (It might be mildly nicer to implement this on `TyCtxt`, and
 165     /// not `InferCtxtBuilder`, but that is a bit tricky right now.
 166     /// In part because we would need a `for<'tcx>` sort of
 167     /// bound for the closure and in part because it is convenient to
 168     /// have `'tcx` be free on this function so that we can talk about
 169     /// `K: TypeFoldable<'tcx>`.)
 170     fn enter_canonical_trait_query<K, R>(
 171         &mut self,
 172         canonical_key: &Canonical<'tcx, K>,
 173         operation: impl FnOnce(&InferCtxt<'tcx>, &mut dyn TraitEngine<'tcx>, K) -> Fallible<R>,
 174     ) -> Fallible<CanonicalizedQueryResponse<'tcx, R>>
 175     where
 176         K: TypeFoldable<'tcx>,
 177         R: Debug + TypeFoldable<'tcx>,
 178         Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>,
 179     {
 180         let (ref infcx, key, canonical_inference_vars) =
 181             self.build_with_canonical(DUMMY_SP, canonical_key);
 182         let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
 183         let value = operation(infcx, &mut *fulfill_cx, key)?;
 184         infcx.make_canonicalized_query_response(canonical_inference_vars, value, &mut *fulfill_cx)
 185     }
 186 }