compiler/rustc_traits/src/type_op.rs

   1 use rustc_hir as hir;
   2 use rustc_hir::def_id::DefId;
   3 use rustc_infer::infer::at::ToTrace;
   4 use rustc_infer::infer::canonical::{Canonical, QueryResponse};
   5 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
   6 use rustc_infer::traits::TraitEngineExt as _;
   7 use rustc_middle::ty::query::Providers;
   8 use rustc_middle::ty::subst::{GenericArg, Subst, UserSelfTy, UserSubsts};
   9 use rustc_middle::ty::{self, FnSig, Lift, PolyFnSig, Ty, TyCtxt, TypeFoldable, Variance};
  10 use rustc_middle::ty::{ParamEnv, ParamEnvAnd, Predicate, ToPredicate};
  11 use rustc_span::DUMMY_SP;
  12 use rustc_trait_selection::infer::InferCtxtBuilderExt;
  13 use rustc_trait_selection::infer::InferCtxtExt;
  14 use rustc_trait_selection::traits::query::normalize::AtExt;
  15 use rustc_trait_selection::traits::query::type_op::ascribe_user_type::AscribeUserType;
  16 use rustc_trait_selection::traits::query::type_op::eq::Eq;
  17 use rustc_trait_selection::traits::query::type_op::normalize::Normalize;
  18 use rustc_trait_selection::traits::query::type_op::prove_predicate::ProvePredicate;
  19 use rustc_trait_selection::traits::query::type_op::subtype::Subtype;
  20 use rustc_trait_selection::traits::query::{Fallible, NoSolution};
  21 use rustc_trait_selection::traits::{Normalized, Obligation, ObligationCause, TraitEngine};
  22 use std::fmt;
  23
  24 crate fn provide(p: &mut Providers) {
  25     *p = Providers {
  26         type_op_ascribe_user_type,
  27         type_op_eq,
  28         type_op_prove_predicate,
  29         type_op_subtype,
  30         type_op_normalize_ty,
  31         type_op_normalize_predicate,
  32         type_op_normalize_fn_sig,
  33         type_op_normalize_poly_fn_sig,
  34         ..*p
  35     };
  36 }
  37
  38 fn type_op_ascribe_user_type<'tcx>(
  39     tcx: TyCtxt<'tcx>,
  40     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, AscribeUserType<'tcx>>>,
  41 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
  42     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |infcx, fulfill_cx, key| {
  43         let (param_env, AscribeUserType { mir_ty, def_id, user_substs }) = key.into_parts();
  44
  45         debug!(
  46             "type_op_ascribe_user_type: mir_ty={:?} def_id={:?} user_substs={:?}",
  47             mir_ty, def_id, user_substs
  48         );
  49
  50         let mut cx = AscribeUserTypeCx { infcx, param_env, fulfill_cx };
  51         cx.relate_mir_and_user_ty(mir_ty, def_id, user_substs)?;
  52
  53         Ok(())
  54     })
  55 }
  56
  57 struct AscribeUserTypeCx<'me, 'tcx> {
  58     infcx: &'me InferCtxt<'me, 'tcx>,
  59     param_env: ParamEnv<'tcx>,
  60     fulfill_cx: &'me mut dyn TraitEngine<'tcx>,
  61 }
  62
  63 impl AscribeUserTypeCx<'me, 'tcx> {
  64     fn normalize<T>(&mut self, value: T) -> T
  65     where
  66         T: TypeFoldable<'tcx>,
  67     {
  68         self.infcx
  69             .partially_normalize_associated_types_in(
  70                 DUMMY_SP,
  71                 hir::CRATE_HIR_ID,
  72                 self.param_env,
  73                 value,
  74             )
  75             .into_value_registering_obligations(self.infcx, self.fulfill_cx)
  76     }
  77
  78     fn relate<T>(&mut self, a: T, variance: Variance, b: T) -> Result<(), NoSolution>
  79     where
  80         T: ToTrace<'tcx>,
  81     {
  82         self.infcx
  83             .at(&ObligationCause::dummy(), self.param_env)
  84             .relate(a, variance, b)?
  85             .into_value_registering_obligations(self.infcx, self.fulfill_cx);
  86         Ok(())
  87     }
  88
  89     fn prove_predicate(&mut self, predicate: Predicate<'tcx>) {
  90         self.fulfill_cx.register_predicate_obligation(
  91             self.infcx,
  92             Obligation::new(ObligationCause::dummy(), self.param_env, predicate),
  93         );
  94     }
  95
  96     fn tcx(&self) -> TyCtxt<'tcx> {
  97         self.infcx.tcx
  98     }
  99
 100     fn subst<T>(&self, value: T, substs: &[GenericArg<'tcx>]) -> T
 101     where
 102         T: TypeFoldable<'tcx>,
 103     {
 104         value.subst(self.tcx(), substs)
 105     }
 106
 107     fn relate_mir_and_user_ty(
 108         &mut self,
 109         mir_ty: Ty<'tcx>,
 110         def_id: DefId,
 111         user_substs: UserSubsts<'tcx>,
 112     ) -> Result<(), NoSolution> {
 113         let UserSubsts { user_self_ty, substs } = user_substs;
 114         let tcx = self.tcx();
 115
 116         let ty = tcx.type_of(def_id);
 117         let ty = self.subst(ty, substs);
 118         debug!("relate_type_and_user_type: ty of def-id is {:?}", ty);
 119         let ty = self.normalize(ty);
 120
 121         self.relate(mir_ty, Variance::Invariant, ty)?;
 122
 123         // Prove the predicates coming along with `def_id`.
 124         //
 125         // Also, normalize the `instantiated_predicates`
 126         // because otherwise we wind up with duplicate "type
 127         // outlives" error messages.
 128         let instantiated_predicates =
 129             self.tcx().predicates_of(def_id).instantiate(self.tcx(), substs);
 130         for instantiated_predicate in instantiated_predicates.predicates {
 131             let instantiated_predicate = self.normalize(instantiated_predicate);
 132             self.prove_predicate(instantiated_predicate);
 133         }
 134
 135         if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
 136             let impl_self_ty = self.tcx().type_of(impl_def_id);
 137             let impl_self_ty = self.subst(impl_self_ty, &substs);
 138             let impl_self_ty = self.normalize(impl_self_ty);
 139
 140             self.relate(self_ty, Variance::Invariant, impl_self_ty)?;
 141
 142             self.prove_predicate(
 143                 ty::PredicateKind::WellFormed(impl_self_ty.into()).to_predicate(self.tcx()),
 144             );
 145         }
 146
 147         // In addition to proving the predicates, we have to
 148         // prove that `ty` is well-formed -- this is because
 149         // the WF of `ty` is predicated on the substs being
 150         // well-formed, and we haven't proven *that*. We don't
 151         // want to prove the WF of types from  `substs` directly because they
 152         // haven't been normalized.
 153         //
 154         // FIXME(nmatsakis): Well, perhaps we should normalize
 155         // them?  This would only be relevant if some input
 156         // type were ill-formed but did not appear in `ty`,
 157         // which...could happen with normalization...
 158         self.prove_predicate(ty::PredicateKind::WellFormed(ty.into()).to_predicate(self.tcx()));
 159         Ok(())
 160     }
 161 }
 162
 163 fn type_op_eq<'tcx>(
 164     tcx: TyCtxt<'tcx>,
 165     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Eq<'tcx>>>,
 166 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
 167     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |infcx, fulfill_cx, key| {
 168         let (param_env, Eq { a, b }) = key.into_parts();
 169         infcx
 170             .at(&ObligationCause::dummy(), param_env)
 171             .eq(a, b)?
 172             .into_value_registering_obligations(infcx, fulfill_cx);
 173         Ok(())
 174     })
 175 }
 176
 177 fn type_op_normalize<T>(
 178     infcx: &InferCtxt<'_, 'tcx>,
 179     fulfill_cx: &mut dyn TraitEngine<'tcx>,
 180     key: ParamEnvAnd<'tcx, Normalize<T>>,
 181 ) -> Fallible<T>
 182 where
 183     T: fmt::Debug + TypeFoldable<'tcx> + Lift<'tcx>,
 184 {
 185     let (param_env, Normalize { value }) = key.into_parts();
 186     let Normalized { value, obligations } =
 187         infcx.at(&ObligationCause::dummy(), param_env).normalize(value)?;
 188     fulfill_cx.register_predicate_obligations(infcx, obligations);
 189     Ok(value)
 190 }
 191
 192 fn type_op_normalize_ty(
 193     tcx: TyCtxt<'tcx>,
 194     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Normalize<Ty<'tcx>>>>,
 195 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>, NoSolution> {
 196     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, type_op_normalize)
 197 }
 198
 199 fn type_op_normalize_predicate(
 200     tcx: TyCtxt<'tcx>,
 201     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Normalize<Predicate<'tcx>>>>,
 202 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, Predicate<'tcx>>>, NoSolution> {
 203     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, type_op_normalize)
 204 }
 205
 206 fn type_op_normalize_fn_sig(
 207     tcx: TyCtxt<'tcx>,
 208     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Normalize<FnSig<'tcx>>>>,
 209 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, FnSig<'tcx>>>, NoSolution> {
 210     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, type_op_normalize)
 211 }
 212
 213 fn type_op_normalize_poly_fn_sig(
 214     tcx: TyCtxt<'tcx>,
 215     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Normalize<PolyFnSig<'tcx>>>>,
 216 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, PolyFnSig<'tcx>>>, NoSolution> {
 217     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, type_op_normalize)
 218 }
 219
 220 fn type_op_subtype<'tcx>(
 221     tcx: TyCtxt<'tcx>,
 222     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Subtype<'tcx>>>,
 223 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
 224     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |infcx, fulfill_cx, key| {
 225         let (param_env, Subtype { sub, sup }) = key.into_parts();
 226         infcx
 227             .at(&ObligationCause::dummy(), param_env)
 228             .sup(sup, sub)?
 229             .into_value_registering_obligations(infcx, fulfill_cx);
 230         Ok(())
 231     })
 232 }
 233
 234 fn type_op_prove_predicate<'tcx>(
 235     tcx: TyCtxt<'tcx>,
 236     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, ProvePredicate<'tcx>>>,
 237 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
 238     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |infcx, fulfill_cx, key| {
 239         let (param_env, ProvePredicate { predicate }) = key.into_parts();
 240         fulfill_cx.register_predicate_obligation(
 241             infcx,
 242             Obligation::new(ObligationCause::dummy(), param_env, predicate),
 243         );
 244         Ok(())
 245     })
 246 }