diff options
Diffstat (limited to 'compiler/rustc_hir_analysis/src/check/dropck.rs')
| -rw-r--r-- | compiler/rustc_hir_analysis/src/check/dropck.rs | 351 |
1 files changed, 112 insertions, 239 deletions
diff --git a/compiler/rustc_hir_analysis/src/check/dropck.rs b/compiler/rustc_hir_analysis/src/check/dropck.rs index 111bf5e5455..e0ba255cc06 100644 --- a/compiler/rustc_hir_analysis/src/check/dropck.rs +++ b/compiler/rustc_hir_analysis/src/check/dropck.rs @@ -1,13 +1,17 @@ // FIXME(@lcnr): Move this module out of `rustc_hir_analysis`. // // We don't do any drop checking during hir typeck. -use crate::hir::def_id::{DefId, LocalDefId}; +use rustc_data_structures::fx::FxHashSet; use rustc_errors::{struct_span_err, ErrorGuaranteed}; -use rustc_middle::ty::error::TypeError; -use rustc_middle::ty::relate::{Relate, RelateResult, TypeRelation}; +use rustc_infer::infer::outlives::env::OutlivesEnvironment; +use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt}; use rustc_middle::ty::subst::SubstsRef; -use rustc_middle::ty::util::IgnoreRegions; -use rustc_middle::ty::{self, Predicate, Ty, TyCtxt}; +use rustc_middle::ty::util::CheckRegions; +use rustc_middle::ty::{self, TyCtxt}; +use rustc_trait_selection::traits::{self, ObligationCtxt}; + +use crate::errors; +use crate::hir::def_id::{DefId, LocalDefId}; /// This function confirms that the `Drop` implementation identified by /// `drop_impl_did` is not any more specialized than the type it is @@ -27,22 +31,34 @@ use rustc_middle::ty::{self, Predicate, Ty, TyCtxt}; /// cannot do `struct S<T>; impl<T:Clone> Drop for S<T> { ... }`). /// pub fn check_drop_impl(tcx: TyCtxt<'_>, drop_impl_did: DefId) -> Result<(), ErrorGuaranteed> { + match tcx.impl_polarity(drop_impl_did) { + ty::ImplPolarity::Positive => {} + ty::ImplPolarity::Negative => { + return Err(tcx.sess.emit_err(errors::DropImplPolarity::Negative { + span: tcx.def_span(drop_impl_did), + })); + } + ty::ImplPolarity::Reservation => { + return Err(tcx.sess.emit_err(errors::DropImplPolarity::Reservation { + span: tcx.def_span(drop_impl_did), + })); + } + } let dtor_self_type = tcx.type_of(drop_impl_did).subst_identity(); - let dtor_predicates = tcx.predicates_of(drop_impl_did); match dtor_self_type.kind() { - ty::Adt(adt_def, self_to_impl_substs) => { + ty::Adt(adt_def, adt_to_impl_substs) => { ensure_drop_params_and_item_params_correspond( tcx, drop_impl_did.expect_local(), adt_def.did(), - self_to_impl_substs, + adt_to_impl_substs, )?; ensure_drop_predicates_are_implied_by_item_defn( tcx, - dtor_predicates, + drop_impl_did.expect_local(), adt_def.did().expect_local(), - self_to_impl_substs, + adt_to_impl_substs, ) } _ => { @@ -52,7 +68,7 @@ pub fn check_drop_impl(tcx: TyCtxt<'_>, drop_impl_did: DefId) -> Result<(), Erro let span = tcx.def_span(drop_impl_did); let reported = tcx.sess.delay_span_bug( span, - &format!("should have been rejected by coherence check: {dtor_self_type}"), + format!("should have been rejected by coherence check: {dtor_self_type}"), ); Err(reported) } @@ -63,9 +79,9 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>( tcx: TyCtxt<'tcx>, drop_impl_did: LocalDefId, self_type_did: DefId, - drop_impl_substs: SubstsRef<'tcx>, + adt_to_impl_substs: SubstsRef<'tcx>, ) -> Result<(), ErrorGuaranteed> { - let Err(arg) = tcx.uses_unique_generic_params(drop_impl_substs, IgnoreRegions::No) else { + let Err(arg) = tcx.uses_unique_generic_params(adt_to_impl_substs, CheckRegions::OnlyEarlyBound) else { return Ok(()) }; @@ -76,15 +92,15 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>( struct_span_err!(tcx.sess, drop_impl_span, E0366, "`Drop` impls cannot be specialized"); match arg { ty::util::NotUniqueParam::DuplicateParam(arg) => { - err.note(&format!("`{arg}` is mentioned multiple times")) + err.note(format!("`{arg}` is mentioned multiple times")) } ty::util::NotUniqueParam::NotParam(arg) => { - err.note(&format!("`{arg}` is not a generic parameter")) + err.note(format!("`{arg}` is not a generic parameter")) } }; err.span_note( item_span, - &format!( + format!( "use the same sequence of generic lifetime, type and const parameters \ as the {self_descr} definition", ), @@ -96,237 +112,94 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>( /// implied by assuming the predicates attached to self_type_did. fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>( tcx: TyCtxt<'tcx>, - dtor_predicates: ty::GenericPredicates<'tcx>, - self_type_did: LocalDefId, - self_to_impl_substs: SubstsRef<'tcx>, + drop_impl_def_id: LocalDefId, + adt_def_id: LocalDefId, + adt_to_impl_substs: SubstsRef<'tcx>, ) -> Result<(), ErrorGuaranteed> { - let mut result = Ok(()); - - // Here is an example, analogous to that from - // `compare_impl_method`. - // - // Consider a struct type: - // - // struct Type<'c, 'b:'c, 'a> { - // x: &'a Contents // (contents are irrelevant; - // y: &'c Cell<&'b Contents>, // only the bounds matter for our purposes.) - // } - // - // and a Drop impl: - // - // impl<'z, 'y:'z, 'x:'y> Drop for P<'z, 'y, 'x> { - // fn drop(&mut self) { self.y.set(self.x); } // (only legal if 'x: 'y) - // } - // - // We start out with self_to_impl_substs, that maps the generic - // parameters of Type to that of the Drop impl. - // - // self_to_impl_substs = {'c => 'z, 'b => 'y, 'a => 'x} - // - // Applying this to the predicates (i.e., assumptions) provided by the item - // definition yields the instantiated assumptions: - // - // ['y : 'z] + let infcx = tcx.infer_ctxt().build(); + let ocx = ObligationCtxt::new(&infcx); + + // Take the param-env of the adt and substitute the substs that show up in + // the implementation's self type. This gives us the assumptions that the + // self ty of the implementation is allowed to know just from it being a + // well-formed adt, since that's all we're allowed to assume while proving + // the Drop implementation is not specialized. // - // We then check all of the predicates of the Drop impl: - // - // ['y:'z, 'x:'y] - // - // and ensure each is in the list of instantiated - // assumptions. Here, `'y:'z` is present, but `'x:'y` is - // absent. So we report an error that the Drop impl injected a - // predicate that is not present on the struct definition. - - // We can assume the predicates attached to struct/enum definition - // hold. - let generic_assumptions = tcx.predicates_of(self_type_did); - - let assumptions_in_impl_context = generic_assumptions.instantiate(tcx, &self_to_impl_substs); - let assumptions_in_impl_context = assumptions_in_impl_context.predicates; - - debug!(?assumptions_in_impl_context, ?dtor_predicates.predicates); - - let self_param_env = tcx.param_env(self_type_did); - - // An earlier version of this code attempted to do this checking - // via the traits::fulfill machinery. However, it ran into trouble - // since the fulfill machinery merely turns outlives-predicates - // 'a:'b and T:'b into region inference constraints. It is simpler - // just to look for all the predicates directly. - - assert_eq!(dtor_predicates.parent, None); - for &(predicate, predicate_sp) in dtor_predicates.predicates { - // (We do not need to worry about deep analysis of type - // expressions etc because the Drop impls are already forced - // to take on a structure that is roughly an alpha-renaming of - // the generic parameters of the item definition.) - - // This path now just checks *all* predicates via an instantiation of - // the `SimpleEqRelation`, which simply forwards to the `relate` machinery - // after taking care of anonymizing late bound regions. - // - // However, it may be more efficient in the future to batch - // the analysis together via the fulfill (see comment above regarding - // the usage of the fulfill machinery), rather than the - // repeated `.iter().any(..)` calls. + // We don't need to normalize this param-env or anything, since we're only + // substituting it with free params, so no additional param-env normalization + // can occur on top of what has been done in the param_env query itself. + let param_env = ty::EarlyBinder(tcx.param_env(adt_def_id)) + .subst(tcx, adt_to_impl_substs) + .with_constness(tcx.constness(drop_impl_def_id)); + + for (pred, span) in tcx.predicates_of(drop_impl_def_id).instantiate_identity(tcx) { + let normalize_cause = traits::ObligationCause::misc(span, adt_def_id); + let pred = ocx.normalize(&normalize_cause, param_env, pred); + let cause = traits::ObligationCause::new(span, adt_def_id, traits::DropImpl); + ocx.register_obligation(traits::Obligation::new(tcx, cause, param_env, pred)); + } - // This closure is a more robust way to check `Predicate` equality - // than simple `==` checks (which were the previous implementation). - // It relies on `ty::relate` for `TraitPredicate`, `ProjectionPredicate`, - // `ConstEvaluatable` and `TypeOutlives` (which implement the Relate trait), - // while delegating on simple equality for the other `Predicate`. - // This implementation solves (Issue #59497) and (Issue #58311). - // It is unclear to me at the moment whether the approach based on `relate` - // could be extended easily also to the other `Predicate`. - let predicate_matches_closure = |p: Predicate<'tcx>| { - let mut relator: SimpleEqRelation<'tcx> = SimpleEqRelation::new(tcx, self_param_env); - let predicate = predicate.kind(); - let p = p.kind(); - match (predicate.skip_binder(), p.skip_binder()) { - ( - ty::PredicateKind::Clause(ty::Clause::Trait(a)), - ty::PredicateKind::Clause(ty::Clause::Trait(b)), - ) => relator.relate(predicate.rebind(a), p.rebind(b)).is_ok(), - ( - ty::PredicateKind::Clause(ty::Clause::Projection(a)), - ty::PredicateKind::Clause(ty::Clause::Projection(b)), - ) => relator.relate(predicate.rebind(a), p.rebind(b)).is_ok(), - ( - ty::PredicateKind::ConstEvaluatable(a), - ty::PredicateKind::ConstEvaluatable(b), - ) => relator.relate(predicate.rebind(a), predicate.rebind(b)).is_ok(), - ( - ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate( - ty_a, - lt_a, - ))), - ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate( - ty_b, - lt_b, - ))), - ) => { - relator.relate(predicate.rebind(ty_a), p.rebind(ty_b)).is_ok() - && relator.relate(predicate.rebind(lt_a), p.rebind(lt_b)).is_ok() - } - (ty::PredicateKind::WellFormed(arg_a), ty::PredicateKind::WellFormed(arg_b)) => { - relator.relate(predicate.rebind(arg_a), p.rebind(arg_b)).is_ok() - } - _ => predicate == p, + // All of the custom error reporting logic is to preserve parity with the old + // error messages. + // + // They can probably get removed with better treatment of the new `DropImpl` + // obligation cause code, and perhaps some custom logic in `report_region_errors`. + + let errors = ocx.select_all_or_error(); + if !errors.is_empty() { + let mut guar = None; + let mut root_predicates = FxHashSet::default(); + for error in errors { + let root_predicate = error.root_obligation.predicate; + if root_predicates.insert(root_predicate) { + let item_span = tcx.def_span(adt_def_id); + let self_descr = tcx.def_descr(adt_def_id.to_def_id()); + guar = Some( + struct_span_err!( + tcx.sess, + error.root_obligation.cause.span, + E0367, + "`Drop` impl requires `{root_predicate}` \ + but the {self_descr} it is implemented for does not", + ) + .span_note(item_span, "the implementor must specify the same requirement") + .emit(), + ); } - }; - - if !assumptions_in_impl_context.iter().copied().any(predicate_matches_closure) { - let item_span = tcx.def_span(self_type_did); - let self_descr = tcx.def_descr(self_type_did.to_def_id()); - let reported = struct_span_err!( - tcx.sess, - predicate_sp, - E0367, - "`Drop` impl requires `{predicate}` but the {self_descr} it is implemented for does not", - ) - .span_note(item_span, "the implementor must specify the same requirement") - .emit(); - result = Err(reported); } + return Err(guar.unwrap()); } - result -} - -/// This is an implementation of the [`TypeRelation`] trait with the -/// aim of simply comparing for equality (without side-effects). -/// -/// It is not intended to be used anywhere else other than here. -pub(crate) struct SimpleEqRelation<'tcx> { - tcx: TyCtxt<'tcx>, - param_env: ty::ParamEnv<'tcx>, -} - -impl<'tcx> SimpleEqRelation<'tcx> { - fn new(tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> SimpleEqRelation<'tcx> { - SimpleEqRelation { tcx, param_env } - } -} - -impl<'tcx> TypeRelation<'tcx> for SimpleEqRelation<'tcx> { - fn tcx(&self) -> TyCtxt<'tcx> { - self.tcx - } - - fn param_env(&self) -> ty::ParamEnv<'tcx> { - self.param_env - } - - fn tag(&self) -> &'static str { - "dropck::SimpleEqRelation" - } - - fn a_is_expected(&self) -> bool { - true - } - - fn relate_with_variance<T: Relate<'tcx>>( - &mut self, - _: ty::Variance, - _info: ty::VarianceDiagInfo<'tcx>, - a: T, - b: T, - ) -> RelateResult<'tcx, T> { - // Here we ignore variance because we require drop impl's types - // to be *exactly* the same as to the ones in the struct definition. - self.relate(a, b) - } - - fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> { - debug!("SimpleEqRelation::tys(a={:?}, b={:?})", a, b); - ty::relate::super_relate_tys(self, a, b) - } - - fn regions( - &mut self, - a: ty::Region<'tcx>, - b: ty::Region<'tcx>, - ) -> RelateResult<'tcx, ty::Region<'tcx>> { - debug!("SimpleEqRelation::regions(a={:?}, b={:?})", a, b); - - // We can just equate the regions because LBRs have been - // already anonymized. - if a == b { - Ok(a) - } else { - // I'm not sure is this `TypeError` is the right one, but - // it should not matter as it won't be checked (the dropck - // will emit its own, more informative and higher-level errors - // in case anything goes wrong). - Err(TypeError::RegionsPlaceholderMismatch) + let errors = ocx.infcx.resolve_regions(&OutlivesEnvironment::new(param_env)); + if !errors.is_empty() { + let mut guar = None; + for error in errors { + let item_span = tcx.def_span(adt_def_id); + let self_descr = tcx.def_descr(adt_def_id.to_def_id()); + let outlives = match error { + RegionResolutionError::ConcreteFailure(_, a, b) => format!("{b}: {a}"), + RegionResolutionError::GenericBoundFailure(_, generic, r) => { + format!("{generic}: {r}") + } + RegionResolutionError::SubSupConflict(_, _, _, a, _, b, _) => format!("{b}: {a}"), + RegionResolutionError::UpperBoundUniverseConflict(a, _, _, _, b) => { + format!("{b}: {a}", a = tcx.mk_re_var(a)) + } + }; + guar = Some( + struct_span_err!( + tcx.sess, + error.origin().span(), + E0367, + "`Drop` impl requires `{outlives}` \ + but the {self_descr} it is implemented for does not", + ) + .span_note(item_span, "the implementor must specify the same requirement") + .emit(), + ); } + return Err(guar.unwrap()); } - fn consts( - &mut self, - a: ty::Const<'tcx>, - b: ty::Const<'tcx>, - ) -> RelateResult<'tcx, ty::Const<'tcx>> { - debug!("SimpleEqRelation::consts(a={:?}, b={:?})", a, b); - ty::relate::super_relate_consts(self, a, b) - } - - fn binders<T>( - &mut self, - a: ty::Binder<'tcx, T>, - b: ty::Binder<'tcx, T>, - ) -> RelateResult<'tcx, ty::Binder<'tcx, T>> - where - T: Relate<'tcx>, - { - debug!("SimpleEqRelation::binders({:?}: {:?}", a, b); - - // Anonymizing the LBRs is necessary to solve (Issue #59497). - // After we do so, it should be totally fine to skip the binders. - let anon_a = self.tcx.anonymize_bound_vars(a); - let anon_b = self.tcx.anonymize_bound_vars(b); - self.relate(anon_a.skip_binder(), anon_b.skip_binder())?; - - Ok(a) - } + Ok(()) } |