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::{DefiningAnchor, InferCtxt, TyCtxtInferExt};
   6 use rustc_infer::traits::{ObligationCauseCode, TraitEngineExt as _};
   7 use rustc_middle::ty::query::Providers;
   8 use rustc_middle::ty::subst::{GenericArg, Subst, UserSelfTy, UserSubsts};
   9 use rustc_middle::ty::{
  10     self, EarlyBinder, FnSig, Lift, PolyFnSig, Ty, TyCtxt, TypeFoldable, Variance,
  11 };
  12 use rustc_middle::ty::{ParamEnv, ParamEnvAnd, Predicate, ToPredicate};
  13 use rustc_span::{Span, DUMMY_SP};
  14 use rustc_trait_selection::infer::InferCtxtBuilderExt;
  15 use rustc_trait_selection::infer::InferCtxtExt;
  16 use rustc_trait_selection::traits::query::normalize::AtExt;
  17 use rustc_trait_selection::traits::query::type_op::ascribe_user_type::AscribeUserType;
  18 use rustc_trait_selection::traits::query::type_op::eq::Eq;
  19 use rustc_trait_selection::traits::query::type_op::normalize::Normalize;
  20 use rustc_trait_selection::traits::query::type_op::prove_predicate::ProvePredicate;
  21 use rustc_trait_selection::traits::query::type_op::subtype::Subtype;
  22 use rustc_trait_selection::traits::query::{Fallible, NoSolution};
  23 use rustc_trait_selection::traits::{Normalized, Obligation, ObligationCause, TraitEngine};
  24 use std::fmt;
  25 use std::iter::zip;
  26
  27 pub(crate) fn provide(p: &mut Providers) {
  28     *p = Providers {
  29         type_op_ascribe_user_type,
  30         type_op_eq,
  31         type_op_prove_predicate,
  32         type_op_subtype,
  33         type_op_normalize_ty,
  34         type_op_normalize_predicate,
  35         type_op_normalize_fn_sig,
  36         type_op_normalize_poly_fn_sig,
  37         ..*p
  38     };
  39 }
  40
  41 fn type_op_ascribe_user_type<'tcx>(
  42     tcx: TyCtxt<'tcx>,
  43     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, AscribeUserType<'tcx>>>,
  44 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
  45     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |infcx, fulfill_cx, key| {
  46         type_op_ascribe_user_type_with_span(infcx, fulfill_cx, key, None)
  47     })
  48 }
  49
  50 /// The core of the `type_op_ascribe_user_type` query: for diagnostics purposes in NLL HRTB errors,
  51 /// this query can be re-run to better track the span of the obligation cause, and improve the error
  52 /// message. Do not call directly unless you're in that very specific context.
  53 pub fn type_op_ascribe_user_type_with_span<'a, 'tcx: 'a>(
  54     infcx: &'a InferCtxt<'a, 'tcx>,
  55     fulfill_cx: &'a mut dyn TraitEngine<'tcx>,
  56     key: ParamEnvAnd<'tcx, AscribeUserType<'tcx>>,
  57     span: Option<Span>,
  58 ) -> Result<(), NoSolution> {
  59     let (param_env, AscribeUserType { mir_ty, def_id, user_substs }) = key.into_parts();
  60     debug!(
  61         "type_op_ascribe_user_type: mir_ty={:?} def_id={:?} user_substs={:?}",
  62         mir_ty, def_id, user_substs
  63     );
  64
  65     let mut cx = AscribeUserTypeCx { infcx, param_env, span: span.unwrap_or(DUMMY_SP), fulfill_cx };
  66     cx.relate_mir_and_user_ty(mir_ty, def_id, user_substs)?;
  67     Ok(())
  68 }
  69
  70 struct AscribeUserTypeCx<'me, 'tcx> {
  71     infcx: &'me InferCtxt<'me, 'tcx>,
  72     param_env: ParamEnv<'tcx>,
  73     span: Span,
  74     fulfill_cx: &'me mut dyn TraitEngine<'tcx>,
  75 }
  76
  77 impl<'me, 'tcx> AscribeUserTypeCx<'me, 'tcx> {
  78     fn normalize<T>(&mut self, value: T) -> T
  79     where
  80         T: TypeFoldable<'tcx>,
  81     {
  82         self.infcx
  83             .partially_normalize_associated_types_in(
  84                 ObligationCause::misc(self.span, hir::CRATE_HIR_ID),
  85                 self.param_env,
  86                 value,
  87             )
  88             .into_value_registering_obligations(self.infcx, self.fulfill_cx)
  89     }
  90
  91     fn relate<T>(&mut self, a: T, variance: Variance, b: T) -> Result<(), NoSolution>
  92     where
  93         T: ToTrace<'tcx>,
  94     {
  95         self.infcx
  96             .at(&ObligationCause::dummy_with_span(self.span), self.param_env)
  97             .relate(a, variance, b)?
  98             .into_value_registering_obligations(self.infcx, self.fulfill_cx);
  99         Ok(())
 100     }
 101
 102     fn prove_predicate(&mut self, predicate: Predicate<'tcx>, cause: ObligationCause<'tcx>) {
 103         self.fulfill_cx.register_predicate_obligation(
 104             self.infcx,
 105             Obligation::new(cause, self.param_env, predicate),
 106         );
 107     }
 108
 109     fn tcx(&self) -> TyCtxt<'tcx> {
 110         self.infcx.tcx
 111     }
 112
 113     fn subst<T>(&self, value: T, substs: &[GenericArg<'tcx>]) -> T
 114     where
 115         T: TypeFoldable<'tcx>,
 116     {
 117         EarlyBinder(value).subst(self.tcx(), substs)
 118     }
 119
 120     #[instrument(level = "debug", skip(self))]
 121     fn relate_mir_and_user_ty(
 122         &mut self,
 123         mir_ty: Ty<'tcx>,
 124         def_id: DefId,
 125         user_substs: UserSubsts<'tcx>,
 126     ) -> Result<(), NoSolution> {
 127         let UserSubsts { user_self_ty, substs } = user_substs;
 128         let tcx = self.tcx();
 129
 130         let ty = tcx.type_of(def_id);
 131         let ty = self.subst(ty, substs);
 132         let ty = self.normalize(ty);
 133         debug!("relate_type_and_user_type: ty of def-id is {:?}", ty);
 134
 135         self.relate(mir_ty, Variance::Invariant, ty)?;
 136
 137         // Prove the predicates coming along with `def_id`.
 138         //
 139         // Also, normalize the `instantiated_predicates`
 140         // because otherwise we wind up with duplicate "type
 141         // outlives" error messages.
 142         let instantiated_predicates =
 143             self.tcx().predicates_of(def_id).instantiate(self.tcx(), substs);
 144
 145         let cause = ObligationCause::dummy_with_span(self.span);
 146
 147         debug!(?instantiated_predicates);
 148         for (instantiated_predicate, predicate_span) in
 149             zip(instantiated_predicates.predicates, instantiated_predicates.spans)
 150         {
 151             let span = if self.span == DUMMY_SP { predicate_span } else { self.span };
 152             let cause = ObligationCause::new(
 153                 span,
 154                 hir::CRATE_HIR_ID,
 155                 ObligationCauseCode::AscribeUserTypeProvePredicate(predicate_span),
 156             );
 157             self.prove_predicate(instantiated_predicate, cause);
 158         }
 159
 160         if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
 161             let impl_self_ty = self.tcx().type_of(impl_def_id);
 162             let impl_self_ty = self.subst(impl_self_ty, &substs);
 163             let impl_self_ty = self.normalize(impl_self_ty);
 164
 165             self.relate(self_ty, Variance::Invariant, impl_self_ty)?;
 166
 167             self.prove_predicate(
 168                 ty::Binder::dummy(ty::PredicateKind::WellFormed(impl_self_ty.into()))
 169                     .to_predicate(self.tcx()),
 170                 cause.clone(),
 171             );
 172         }
 173
 174         // In addition to proving the predicates, we have to
 175         // prove that `ty` is well-formed -- this is because
 176         // the WF of `ty` is predicated on the substs being
 177         // well-formed, and we haven't proven *that*. We don't
 178         // want to prove the WF of types from  `substs` directly because they
 179         // haven't been normalized.
 180         //
 181         // FIXME(nmatsakis): Well, perhaps we should normalize
 182         // them?  This would only be relevant if some input
 183         // type were ill-formed but did not appear in `ty`,
 184         // which...could happen with normalization...
 185         self.prove_predicate(
 186             ty::Binder::dummy(ty::PredicateKind::WellFormed(ty.into())).to_predicate(self.tcx()),
 187             cause,
 188         );
 189         Ok(())
 190     }
 191 }
 192
 193 fn type_op_eq<'tcx>(
 194     tcx: TyCtxt<'tcx>,
 195     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Eq<'tcx>>>,
 196 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
 197     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |infcx, fulfill_cx, key| {
 198         let (param_env, Eq { a, b }) = key.into_parts();
 199         infcx
 200             .at(&ObligationCause::dummy(), param_env)
 201             .eq(a, b)?
 202             .into_value_registering_obligations(infcx, fulfill_cx);
 203         Ok(())
 204     })
 205 }
 206
 207 fn type_op_normalize<'tcx, T>(
 208     infcx: &InferCtxt<'_, 'tcx>,
 209     fulfill_cx: &mut dyn TraitEngine<'tcx>,
 210     key: ParamEnvAnd<'tcx, Normalize<T>>,
 211 ) -> Fallible<T>
 212 where
 213     T: fmt::Debug + TypeFoldable<'tcx> + Lift<'tcx>,
 214 {
 215     let (param_env, Normalize { value }) = key.into_parts();
 216     let Normalized { value, obligations } =
 217         infcx.at(&ObligationCause::dummy(), param_env).normalize(value)?;
 218     fulfill_cx.register_predicate_obligations(infcx, obligations);
 219     Ok(value)
 220 }
 221
 222 fn type_op_normalize_ty<'tcx>(
 223     tcx: TyCtxt<'tcx>,
 224     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Normalize<Ty<'tcx>>>>,
 225 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>, NoSolution> {
 226     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, type_op_normalize)
 227 }
 228
 229 fn type_op_normalize_predicate<'tcx>(
 230     tcx: TyCtxt<'tcx>,
 231     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Normalize<Predicate<'tcx>>>>,
 232 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, Predicate<'tcx>>>, NoSolution> {
 233     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, type_op_normalize)
 234 }
 235
 236 fn type_op_normalize_fn_sig<'tcx>(
 237     tcx: TyCtxt<'tcx>,
 238     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Normalize<FnSig<'tcx>>>>,
 239 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, FnSig<'tcx>>>, NoSolution> {
 240     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, type_op_normalize)
 241 }
 242
 243 fn type_op_normalize_poly_fn_sig<'tcx>(
 244     tcx: TyCtxt<'tcx>,
 245     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Normalize<PolyFnSig<'tcx>>>>,
 246 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, PolyFnSig<'tcx>>>, NoSolution> {
 247     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, type_op_normalize)
 248 }
 249
 250 fn type_op_subtype<'tcx>(
 251     tcx: TyCtxt<'tcx>,
 252     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, Subtype<'tcx>>>,
 253 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
 254     tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |infcx, fulfill_cx, key| {
 255         let (param_env, Subtype { sub, sup }) = key.into_parts();
 256         infcx
 257             .at(&ObligationCause::dummy(), param_env)
 258             .sup(sup, sub)?
 259             .into_value_registering_obligations(infcx, fulfill_cx);
 260         Ok(())
 261     })
 262 }
 263
 264 fn type_op_prove_predicate<'tcx>(
 265     tcx: TyCtxt<'tcx>,
 266     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, ProvePredicate<'tcx>>>,
 267 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
 268     // HACK This bubble is required for this test to pass:
 269     // impl-trait/issue-99642.rs
 270     tcx.infer_ctxt().with_opaque_type_inference(DefiningAnchor::Bubble).enter_canonical_trait_query(
 271         &canonicalized,
 272         |infcx, fulfill_cx, key| {
 273             type_op_prove_predicate_with_cause(infcx, fulfill_cx, key, ObligationCause::dummy());
 274             Ok(())
 275         },
 276     )
 277 }
 278
 279 /// The core of the `type_op_prove_predicate` query: for diagnostics purposes in NLL HRTB errors,
 280 /// this query can be re-run to better track the span of the obligation cause, and improve the error
 281 /// message. Do not call directly unless you're in that very specific context.
 282 pub fn type_op_prove_predicate_with_cause<'a, 'tcx: 'a>(
 283     infcx: &'a InferCtxt<'a, 'tcx>,
 284     fulfill_cx: &'a mut dyn TraitEngine<'tcx>,
 285     key: ParamEnvAnd<'tcx, ProvePredicate<'tcx>>,
 286     cause: ObligationCause<'tcx>,
 287 ) {
 288     let (param_env, ProvePredicate { predicate }) = key.into_parts();
 289     fulfill_cx.register_predicate_obligation(infcx, Obligation::new(cause, param_env, predicate));
 290 }