diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs index 29936fadc57..f2cb28fd6f6 100644 --- a/compiler/rustc_infer/src/infer/mod.rs +++ b/compiler/rustc_infer/src/infer/mod.rs @@ -1011,8 +1011,8 @@ pub fn var_for_effect(&self, param: &ty::GenericParamDef) -> GenericArg<'tcx> { ty::Const::new_infer(self.tcx, ty::InferConst::EffectVar(effect_vid)).into() } - /// Given a set of generics defined on a type or impl, returns the generic parameters mapping each - /// type/region parameter to a fresh inference variable. + /// Given a set of generics defined on a type or impl, returns the generic parameters mapping + /// each type/region parameter to a fresh inference variable. pub fn fresh_args_for_item(&self, span: Span, def_id: DefId) -> GenericArgsRef<'tcx> { GenericArgs::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param)) } @@ -1390,10 +1390,10 @@ pub fn try_const_eval_resolve( /// /// The constant can be located on a trait like `::C`, in which case the given /// generic parameters and environment are used to resolve the constant. Alternatively if the - /// constant has generic parameters in scope the instantiations are used to evaluate the value of - /// the constant. For example in `fn foo() { let _ = [0; bar::()]; }` the repeat count - /// constant `bar::()` requires a instantiation for `T`, if the instantiation for `T` is still - /// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is + /// constant has generic parameters in scope the instantiations are used to evaluate the value + /// of the constant. For example in `fn foo() { let _ = [0; bar::()]; }` the repeat count + /// constant `bar::()` requires a instantiation for `T`, if the instantiation for `T` is + /// still too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is /// returned. /// /// This handles inferences variables within both `param_env` and `args` by diff --git a/compiler/rustc_infer/src/infer/opaque_types/mod.rs b/compiler/rustc_infer/src/infer/opaque_types/mod.rs index 5a2ffbf029e..365ddaba138 100644 --- a/compiler/rustc_infer/src/infer/opaque_types/mod.rs +++ b/compiler/rustc_infer/src/infer/opaque_types/mod.rs @@ -148,11 +148,11 @@ pub fn handle_opaque_type( } if let ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, .. }) = *b.kind() { - // We could accept this, but there are various ways to handle this situation, and we don't - // want to make a decision on it right now. Likely this case is so super rare anyway, that - // no one encounters it in practice. - // It does occur however in `fn fut() -> impl Future { async { 42 } }`, - // where it is of no concern, so we only check for TAITs. + // We could accept this, but there are various ways to handle this situation, + // and we don't want to make a decision on it right now. Likely this case is so + // super rare anyway, that no one encounters it in practice. It does occur + // however in `fn fut() -> impl Future { async { 42 } }`, where + // it is of no concern, so we only check for TAITs. if self.can_define_opaque_ty(b_def_id) && self.tcx.is_type_alias_impl_trait(b_def_id) { diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs index 634cda86bc3..e0e03a29220 100644 --- a/compiler/rustc_infer/src/infer/outlives/obligations.rs +++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs @@ -396,11 +396,12 @@ fn alias_ty_must_outlive( // 'a` in the environment but `trait Foo<'b> { type Item: 'b // }` in the trait definition. approx_env_bounds.retain(|bound_outlives| { - // OK to skip binder because we only manipulate and compare against other - // values from the same binder. e.g. if we have (e.g.) `for<'a> >::Item: 'a` - // in `bound`, the `'a` will be a `^1` (bound, debruijn index == innermost) region. - // If the declaration is `trait Trait<'b> { type Item: 'b; }`, then `projection_declared_bounds_from_trait` - // will be invoked with `['b => ^1]` and so we will get `^1` returned. + // OK to skip binder because we only manipulate and compare against other values from + // the same binder. e.g. if we have (e.g.) `for<'a> >::Item: 'a` in + // `bound`, the `'a` will be a `^1` (bound, debruijn index == innermost) region. If the + // declaration is `trait Trait<'b> { type Item: 'b; }`, then + // `projection_declared_bounds_from_trait` will be invoked with `['b => ^1]` and so we + // will get `^1` returned. let bound = bound_outlives.skip_binder(); let ty::Alias(_, alias_ty) = bound.0.kind() else { bug!("expected AliasTy") }; self.verify_bound.declared_bounds_from_definition(*alias_ty).all(|r| r != bound.1) diff --git a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs index 7913f0e340e..30eba3e8f4f 100644 --- a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs +++ b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs @@ -55,8 +55,8 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> { /// * what placeholder they must outlive transitively /// * if they must also be equal to a placeholder, report an error because `P1: P2` /// * minimum universe U of all SCCs they must outlive - /// * if they must also be equal to a placeholder P, and U cannot name P, report an error, as that - /// indicates `P: R` and `R` is in an incompatible universe + /// * if they must also be equal to a placeholder P, and U cannot name P, report an error, as + /// that indicates `P: R` and `R` is in an incompatible universe /// /// To improve performance and for the old trait solver caching to be sound, this takes /// an optional snapshot in which case we only look at region constraints added in that @@ -216,8 +216,8 @@ fn propagate_scc_value(&mut self) -> RelateResult<'tcx, ()> { // Walk over each `scc2` such that `scc1: scc2` and compute: // // * `scc1_universe`: the minimum universe of `scc2` and the constituents of `scc1` - // * `succ_bound`: placeholder `P` that the successors must outlive, if any (if there are multiple, - // we pick one arbitrarily) + // * `succ_bound`: placeholder `P` that the successors must outlive, if any (if there + // are multiple, we pick one arbitrarily) let mut scc1_universe = self.scc_universes[scc1]; let mut succ_bound = None; for &scc2 in self.mini_graph.sccs.successors(scc1) { @@ -260,7 +260,8 @@ fn propagate_scc_value(&mut self) -> RelateResult<'tcx, ()> { self.scc_placeholders[scc1] = succ_bound; } - // At this point, `scc_placeholder[scc1]` stores some placeholder that `scc1` must outlive (if any). + // At this point, `scc_placeholder[scc1]` stores some placeholder that `scc1` must + // outlive (if any). } Ok(()) } diff --git a/compiler/rustc_infer/src/infer/relate/generalize.rs b/compiler/rustc_infer/src/infer/relate/generalize.rs index a6d10aa5968..726a2296d11 100644 --- a/compiler/rustc_infer/src/infer/relate/generalize.rs +++ b/compiler/rustc_infer/src/infer/relate/generalize.rs @@ -50,7 +50,8 @@ pub fn instantiate_ty_var>>( // Then the `generalized_ty` would be `&'?2 ?3`, where `'?2` and `?3` are fresh // region/type inference variables. // - // We then relate `generalized_ty <: source_ty`,adding constraints like `'x: '?2` and `?1 <: ?3`. + // We then relate `generalized_ty <: source_ty`, adding constraints like `'x: '?2` and + // `?1 <: ?3`. let Generalization { value_may_be_infer: generalized_ty, has_unconstrained_ty_var } = self .generalize( relation.span(), @@ -104,7 +105,8 @@ pub fn instantiate_ty_var>>( &ty::Alias(ty::Projection, data) => { // FIXME: This does not handle subtyping correctly, we could // instead create a new inference variable `?normalized_source`, emitting - // `Projection(normalized_source, ?ty_normalized)` and `?normalized_source <: generalized_ty`. + // `Projection(normalized_source, ?ty_normalized)` and + // `?normalized_source <: generalized_ty`. relation.register_predicates([ty::ProjectionPredicate { projection_term: data.into(), term: generalized_ty.into(), diff --git a/compiler/rustc_infer/src/traits/project.rs b/compiler/rustc_infer/src/traits/project.rs index fa813d0f90c..64b72de3986 100644 --- a/compiler/rustc_infer/src/traits/project.rs +++ b/compiler/rustc_infer/src/traits/project.rs @@ -92,38 +92,31 @@ pub enum ProjectionCacheEntry<'tcx> { Error, NormalizedTerm { ty: NormalizedTerm<'tcx>, - /// If we were able to successfully evaluate the - /// corresponding cache entry key during predicate - /// evaluation, then this field stores the final - /// result obtained from evaluating all of the projection - /// sub-obligations. During evaluation, we will skip - /// evaluating the cached sub-obligations in `ty` - /// if this field is set. Evaluation only - /// cares about the final result, so we don't - /// care about any region constraint side-effects - /// produced by evaluating the sub-obligations. - /// - /// Additionally, we will clear out the sub-obligations - /// entirely if we ever evaluate the cache entry (along - /// with all its sub obligations) to `EvaluatedToOk`. - /// This affects all users of the cache, not just evaluation. - /// Since a result of `EvaluatedToOk` means that there were - /// no region obligations that need to be tracked, it's - /// fine to forget about the sub-obligations - they - /// don't provide any additional information. However, - /// we do *not* discard any obligations when we see - /// `EvaluatedToOkModuloRegions` - we don't know - /// which sub-obligations may introduce region constraints, - /// so we keep them all to be safe. - /// - /// When we are not performing evaluation - /// (e.g. in `FulfillmentContext`), we ignore this field, - /// and always re-process the cached sub-obligations - /// (which may have been cleared out - see the above - /// paragraph). - /// This ensures that we do not lose any regions - /// constraints that arise from processing the + /// If we were able to successfully evaluate the corresponding cache + /// entry key during predicate evaluation, then this field stores the + /// final result obtained from evaluating all of the projection + /// sub-obligations. During evaluation, we will skip evaluating the + /// cached sub-obligations in `ty` if this field is set. Evaluation + /// only cares about the final result, so we don't care about any + /// region constraint side-effects produced by evaluating the /// sub-obligations. + /// + /// Additionally, we will clear out the sub-obligations entirely if we + /// ever evaluate the cache entry (along with all its sub obligations) + /// to `EvaluatedToOk`. This affects all users of the cache, not just + /// evaluation. Since a result of `EvaluatedToOk` means that there were + /// no region obligations that need to be tracked, it's fine to forget + /// about the sub-obligations - they don't provide any additional + /// information. However, we do *not* discard any obligations when we + /// see `EvaluatedToOkModuloRegions` - we don't know which + /// sub-obligations may introduce region constraints, so we keep them + /// all to be safe. + /// + /// When we are not performing evaluation (e.g. in + /// `FulfillmentContext`), we ignore this field, and always re-process + /// the cached sub-obligations (which may have been cleared out - see + /// the above paragraph). This ensures that we do not lose any regions + /// constraints that arise from processing the sub-obligations. complete: Option, }, }