| //! Generalized type folding mechanism. The setup is a bit convoluted |
| //! but allows for convenient usage. Let T be an instance of some |
| //! "foldable type" (one which implements `TypeFoldable`) and F be an |
| //! instance of a "folder" (a type which implements `TypeFolder`). Then |
| //! the setup is intended to be: |
| //! |
| //! T.fold_with(F) --calls--> F.fold_T(T) --calls--> T.super_fold_with(F) |
| //! |
| //! This way, when you define a new folder F, you can override |
| //! `fold_T()` to customize the behavior, and invoke `T.super_fold_with()` |
| //! to get the original behavior. Meanwhile, to actually fold |
| //! something, you can just write `T.fold_with(F)`, which is |
| //! convenient. (Note that `fold_with` will also transparently handle |
| //! things like a `Vec<T>` where T is foldable and so on.) |
| //! |
| //! In this ideal setup, the only function that actually *does* |
| //! anything is `T.super_fold_with()`, which traverses the type `T`. |
| //! Moreover, `T.super_fold_with()` should only ever call `T.fold_with()`. |
| //! |
| //! In some cases, we follow a degenerate pattern where we do not have |
| //! a `fold_T` method. Instead, `T.fold_with` traverses the structure directly. |
| //! This is suboptimal because the behavior cannot be overridden, but it's |
| //! much less work to implement. If you ever *do* need an override that |
| //! doesn't exist, it's not hard to convert the degenerate pattern into the |
| //! proper thing. |
| //! |
| //! A `TypeFoldable` T can also be visited by a `TypeVisitor` V using similar setup: |
| //! |
| //! T.visit_with(V) --calls--> V.visit_T(T) --calls--> T.super_visit_with(V). |
| //! |
| //! These methods return true to indicate that the visitor has found what it is |
| //! looking for, and does not need to visit anything else. |
| use crate::mir; |
| use crate::ty::{self, flags::FlagComputation, Binder, Ty, TyCtxt, TypeFlags}; |
| use rustc_hir as hir; |
| use rustc_hir::def_id::DefId; |
| |
| use rustc_data_structures::fx::FxHashSet; |
| use rustc_data_structures::sso::SsoHashSet; |
| use std::collections::BTreeMap; |
| use std::fmt; |
| use std::ops::ControlFlow; |
| |
| /// This trait is implemented for every type that can be folded. |
| /// Basically, every type that has a corresponding method in `TypeFolder`. |
| /// |
| /// To implement this conveniently, use the derive macro located in `rustc_macros`. |
| pub trait TypeFoldable<'tcx>: fmt::Debug + Clone { |
| /// Consumers may find this more convenient to use with infallible folders than |
| /// [`try_super_fold_with`][`TypeFoldable::try_super_fold_with`], to which the |
| /// provided default definition delegates. Implementors **should not** override |
| /// this provided default definition, to ensure that the two methods are coherent |
| /// (provide a definition of `try_super_fold_with` instead). |
| fn super_fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self { |
| self.try_super_fold_with(folder).into_ok() |
| } |
| /// Consumers may find this more convenient to use with infallible folders than |
| /// [`try_fold_with`][`TypeFoldable::try_fold_with`], to which the provided |
| /// default definition delegates. Implementors **should not** override this |
| /// provided default definition, to ensure that the two methods are coherent |
| /// (provide a definition of `try_fold_with` instead). |
| fn fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self { |
| self.try_fold_with(folder).into_ok() |
| } |
| |
| fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>( |
| self, |
| folder: &mut F, |
| ) -> Result<Self, F::Error>; |
| |
| fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> { |
| self.try_super_fold_with(folder) |
| } |
| |
| fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy>; |
| fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> { |
| self.super_visit_with(visitor) |
| } |
| |
| /// Returns `true` if `self` has any late-bound regions that are either |
| /// bound by `binder` or bound by some binder outside of `binder`. |
| /// If `binder` is `ty::INNERMOST`, this indicates whether |
| /// there are any late-bound regions that appear free. |
| fn has_vars_bound_at_or_above(&self, binder: ty::DebruijnIndex) -> bool { |
| self.visit_with(&mut HasEscapingVarsVisitor { outer_index: binder }).is_break() |
| } |
| |
| /// Returns `true` if this `self` has any regions that escape `binder` (and |
| /// hence are not bound by it). |
| fn has_vars_bound_above(&self, binder: ty::DebruijnIndex) -> bool { |
| self.has_vars_bound_at_or_above(binder.shifted_in(1)) |
| } |
| |
| fn has_escaping_bound_vars(&self) -> bool { |
| self.has_vars_bound_at_or_above(ty::INNERMOST) |
| } |
| |
| fn definitely_has_type_flags(&self, tcx: TyCtxt<'tcx>, flags: TypeFlags) -> bool { |
| self.visit_with(&mut HasTypeFlagsVisitor { tcx: Some(tcx), flags }).break_value() |
| == Some(FoundFlags) |
| } |
| |
| #[instrument(level = "trace")] |
| fn has_type_flags(&self, flags: TypeFlags) -> bool { |
| self.visit_with(&mut HasTypeFlagsVisitor { tcx: None, flags }).break_value() |
| == Some(FoundFlags) |
| } |
| fn has_projections(&self) -> bool { |
| self.has_type_flags(TypeFlags::HAS_PROJECTION) |
| } |
| fn has_opaque_types(&self) -> bool { |
| self.has_type_flags(TypeFlags::HAS_TY_OPAQUE) |
| } |
| fn references_error(&self) -> bool { |
| self.has_type_flags(TypeFlags::HAS_ERROR) |
| } |
| fn potentially_has_param_types_or_consts(&self) -> bool { |
| self.has_type_flags( |
| TypeFlags::HAS_KNOWN_TY_PARAM |
| | TypeFlags::HAS_KNOWN_CT_PARAM |
| | TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS, |
| ) |
| } |
| fn definitely_has_param_types_or_consts(&self, tcx: TyCtxt<'tcx>) -> bool { |
| self.definitely_has_type_flags( |
| tcx, |
| TypeFlags::HAS_KNOWN_TY_PARAM | TypeFlags::HAS_KNOWN_CT_PARAM, |
| ) |
| } |
| fn has_infer_regions(&self) -> bool { |
| self.has_type_flags(TypeFlags::HAS_RE_INFER) |
| } |
| fn has_infer_types(&self) -> bool { |
| self.has_type_flags(TypeFlags::HAS_TY_INFER) |
| } |
| fn has_infer_types_or_consts(&self) -> bool { |
| self.has_type_flags(TypeFlags::HAS_TY_INFER | TypeFlags::HAS_CT_INFER) |
| } |
| fn needs_infer(&self) -> bool { |
| self.has_type_flags(TypeFlags::NEEDS_INFER) |
| } |
| fn has_placeholders(&self) -> bool { |
| self.has_type_flags( |
| TypeFlags::HAS_RE_PLACEHOLDER |
| | TypeFlags::HAS_TY_PLACEHOLDER |
| | TypeFlags::HAS_CT_PLACEHOLDER, |
| ) |
| } |
| fn potentially_needs_subst(&self) -> bool { |
| self.has_type_flags( |
| TypeFlags::KNOWN_NEEDS_SUBST | TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS, |
| ) |
| } |
| fn definitely_needs_subst(&self, tcx: TyCtxt<'tcx>) -> bool { |
| self.definitely_has_type_flags(tcx, TypeFlags::KNOWN_NEEDS_SUBST) |
| } |
| /// "Free" regions in this context means that it has any region |
| /// that is not (a) erased or (b) late-bound. |
| fn has_free_regions(&self, tcx: TyCtxt<'tcx>) -> bool { |
| self.definitely_has_type_flags(tcx, TypeFlags::HAS_KNOWN_FREE_REGIONS) |
| } |
| |
| fn has_erased_regions(&self) -> bool { |
| self.has_type_flags(TypeFlags::HAS_RE_ERASED) |
| } |
| |
| /// True if there are any un-erased free regions. |
| fn has_erasable_regions(&self, tcx: TyCtxt<'tcx>) -> bool { |
| self.definitely_has_type_flags(tcx, TypeFlags::HAS_KNOWN_FREE_REGIONS) |
| } |
| |
| /// Indicates whether this value definitely references only 'global' |
| /// generic parameters that are the same regardless of what fn we are |
| /// in. This is used for caching. |
| /// |
| /// Note that this function is pessimistic and may incorrectly return |
| /// `false`. |
| fn is_known_global(&self) -> bool { |
| !self.has_type_flags(TypeFlags::HAS_POTENTIAL_FREE_LOCAL_NAMES) |
| } |
| |
| /// Indicates whether this value references only 'global' |
| /// generic parameters that are the same regardless of what fn we are |
| /// in. This is used for caching. |
| fn is_global(&self, tcx: TyCtxt<'tcx>) -> bool { |
| !self.definitely_has_type_flags(tcx, TypeFlags::HAS_KNOWN_FREE_LOCAL_NAMES) |
| } |
| |
| /// True if there are any late-bound regions |
| fn has_late_bound_regions(&self) -> bool { |
| self.has_type_flags(TypeFlags::HAS_RE_LATE_BOUND) |
| } |
| |
| /// Indicates whether this value still has parameters/placeholders/inference variables |
| /// which could be replaced later, in a way that would change the results of `impl` |
| /// specialization. |
| fn still_further_specializable(&self) -> bool { |
| self.has_type_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE) |
| } |
| } |
| |
| impl<'tcx> TypeFoldable<'tcx> for hir::Constness { |
| fn try_super_fold_with<F: TypeFolder<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> { |
| Ok(self) |
| } |
| fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::BreakTy> { |
| ControlFlow::CONTINUE |
| } |
| } |
| |
| /// The `TypeFolder` trait defines the actual *folding*. There is a |
| /// method defined for every foldable type. Each of these has a |
| /// default implementation that does an "identity" fold. Within each |
| /// identity fold, it should invoke `foo.fold_with(self)` to fold each |
| /// sub-item. |
| /// |
| /// If this folder is fallible (and therefore its [`Error`][`TypeFolder::Error`] |
| /// associated type is something other than the default, never), |
| /// [`FallibleTypeFolder`] should be implemented manually; otherwise, |
| /// a blanket implementation of [`FallibleTypeFolder`] will defer to |
| /// the infallible methods of this trait to ensure that the two APIs |
| /// are coherent. |
| pub trait TypeFolder<'tcx>: Sized { |
| type Error = !; |
| |
| fn tcx<'a>(&'a self) -> TyCtxt<'tcx>; |
| |
| fn fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Binder<'tcx, T> |
| where |
| T: TypeFoldable<'tcx>, |
| Self: TypeFolder<'tcx, Error = !>, |
| { |
| t.super_fold_with(self) |
| } |
| |
| fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> |
| where |
| Self: TypeFolder<'tcx, Error = !>, |
| { |
| t.super_fold_with(self) |
| } |
| |
| fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> |
| where |
| Self: TypeFolder<'tcx, Error = !>, |
| { |
| r.super_fold_with(self) |
| } |
| |
| fn fold_const(&mut self, c: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> |
| where |
| Self: TypeFolder<'tcx, Error = !>, |
| { |
| c.super_fold_with(self) |
| } |
| |
| fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> |
| where |
| Self: TypeFolder<'tcx, Error = !>, |
| { |
| p.super_fold_with(self) |
| } |
| |
| fn fold_mir_const(&mut self, c: mir::ConstantKind<'tcx>) -> mir::ConstantKind<'tcx> |
| where |
| Self: TypeFolder<'tcx, Error = !>, |
| { |
| bug!("most type folders should not be folding MIR datastructures: {:?}", c) |
| } |
| } |
| |
| /// The `FallibleTypeFolder` trait defines the actual *folding*. There is a |
| /// method defined for every foldable type. Each of these has a |
| /// default implementation that does an "identity" fold. Within each |
| /// identity fold, it should invoke `foo.try_fold_with(self)` to fold each |
| /// sub-item. |
| /// |
| /// A blanket implementation of this trait (that defers to the relevant |
| /// method of [`TypeFolder`]) is provided for all infallible folders in |
| /// order to ensure the two APIs are coherent. |
| pub trait FallibleTypeFolder<'tcx>: TypeFolder<'tcx> { |
| fn try_fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Result<Binder<'tcx, T>, Self::Error> |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| t.try_super_fold_with(self) |
| } |
| |
| fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> { |
| t.try_super_fold_with(self) |
| } |
| |
| fn try_fold_region(&mut self, r: ty::Region<'tcx>) -> Result<ty::Region<'tcx>, Self::Error> { |
| r.try_super_fold_with(self) |
| } |
| |
| fn try_fold_const( |
| &mut self, |
| c: &'tcx ty::Const<'tcx>, |
| ) -> Result<&'tcx ty::Const<'tcx>, Self::Error> { |
| c.try_super_fold_with(self) |
| } |
| |
| fn try_fold_predicate( |
| &mut self, |
| p: ty::Predicate<'tcx>, |
| ) -> Result<ty::Predicate<'tcx>, Self::Error> { |
| p.try_super_fold_with(self) |
| } |
| |
| fn try_fold_mir_const( |
| &mut self, |
| c: mir::ConstantKind<'tcx>, |
| ) -> Result<mir::ConstantKind<'tcx>, Self::Error> { |
| bug!("most type folders should not be folding MIR datastructures: {:?}", c) |
| } |
| } |
| |
| // Blanket implementation of fallible trait for infallible folders |
| // delegates to infallible methods to prevent incoherence |
| impl<'tcx, F> FallibleTypeFolder<'tcx> for F |
| where |
| F: TypeFolder<'tcx, Error = !>, |
| { |
| fn try_fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Result<Binder<'tcx, T>, Self::Error> |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| Ok(self.fold_binder(t)) |
| } |
| |
| fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> { |
| Ok(self.fold_ty(t)) |
| } |
| |
| fn try_fold_region(&mut self, r: ty::Region<'tcx>) -> Result<ty::Region<'tcx>, Self::Error> { |
| Ok(self.fold_region(r)) |
| } |
| |
| fn try_fold_const( |
| &mut self, |
| c: &'tcx ty::Const<'tcx>, |
| ) -> Result<&'tcx ty::Const<'tcx>, Self::Error> { |
| Ok(self.fold_const(c)) |
| } |
| |
| fn try_fold_predicate( |
| &mut self, |
| p: ty::Predicate<'tcx>, |
| ) -> Result<ty::Predicate<'tcx>, Self::Error> { |
| Ok(self.fold_predicate(p)) |
| } |
| |
| fn try_fold_mir_const( |
| &mut self, |
| c: mir::ConstantKind<'tcx>, |
| ) -> Result<mir::ConstantKind<'tcx>, Self::Error> { |
| Ok(self.fold_mir_const(c)) |
| } |
| } |
| |
| pub trait TypeVisitor<'tcx>: Sized { |
| type BreakTy = !; |
| /// Supplies the `tcx` for an unevaluated anonymous constant in case its default substs |
| /// are not yet supplied. |
| /// |
| /// Returning `None` for this method is only recommended if the `TypeVisitor` |
| /// does not care about default anon const substs, as it ignores generic parameters, |
| /// and fetching the default substs would cause a query cycle. |
| /// |
| /// For visitors which return `None` we completely skip the default substs in `ty::Unevaluated::super_visit_with`. |
| /// This means that incorrectly returning `None` can very quickly lead to ICE or other critical bugs, so be careful and |
| /// try to return an actual `tcx` if possible. |
| fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>>; |
| |
| fn visit_binder<T: TypeFoldable<'tcx>>( |
| &mut self, |
| t: &Binder<'tcx, T>, |
| ) -> ControlFlow<Self::BreakTy> { |
| t.super_visit_with(self) |
| } |
| |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| t.super_visit_with(self) |
| } |
| |
| fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { |
| r.super_visit_with(self) |
| } |
| |
| fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> { |
| c.super_visit_with(self) |
| } |
| |
| fn visit_unevaluated_const(&mut self, uv: ty::Unevaluated<'tcx>) -> ControlFlow<Self::BreakTy> { |
| uv.super_visit_with(self) |
| } |
| |
| fn visit_predicate(&mut self, p: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> { |
| p.super_visit_with(self) |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Some sample folders |
| |
| pub struct BottomUpFolder<'tcx, F, G, H> |
| where |
| F: FnMut(Ty<'tcx>) -> Ty<'tcx>, |
| G: FnMut(ty::Region<'tcx>) -> ty::Region<'tcx>, |
| H: FnMut(&'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx>, |
| { |
| pub tcx: TyCtxt<'tcx>, |
| pub ty_op: F, |
| pub lt_op: G, |
| pub ct_op: H, |
| } |
| |
| impl<'tcx, F, G, H> TypeFolder<'tcx> for BottomUpFolder<'tcx, F, G, H> |
| where |
| F: FnMut(Ty<'tcx>) -> Ty<'tcx>, |
| G: FnMut(ty::Region<'tcx>) -> ty::Region<'tcx>, |
| H: FnMut(&'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx>, |
| { |
| fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { |
| self.tcx |
| } |
| |
| fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { |
| let t = ty.super_fold_with(self); |
| (self.ty_op)(t) |
| } |
| |
| fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { |
| let r = r.super_fold_with(self); |
| (self.lt_op)(r) |
| } |
| |
| fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> { |
| let ct = ct.super_fold_with(self); |
| (self.ct_op)(ct) |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Region folder |
| |
| impl<'tcx> TyCtxt<'tcx> { |
| /// Folds the escaping and free regions in `value` using `f`, and |
| /// sets `skipped_regions` to true if any late-bound region was found |
| /// and skipped. |
| pub fn fold_regions<T>( |
| self, |
| value: T, |
| skipped_regions: &mut bool, |
| mut f: impl FnMut(ty::Region<'tcx>, ty::DebruijnIndex) -> ty::Region<'tcx>, |
| ) -> T |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| value.fold_with(&mut RegionFolder::new(self, skipped_regions, &mut f)) |
| } |
| |
| /// Invoke `callback` on every region appearing free in `value`. |
| pub fn for_each_free_region( |
| self, |
| value: &impl TypeFoldable<'tcx>, |
| mut callback: impl FnMut(ty::Region<'tcx>), |
| ) { |
| self.any_free_region_meets(value, |r| { |
| callback(r); |
| false |
| }); |
| } |
| |
| /// Returns `true` if `callback` returns true for every region appearing free in `value`. |
| pub fn all_free_regions_meet( |
| self, |
| value: &impl TypeFoldable<'tcx>, |
| mut callback: impl FnMut(ty::Region<'tcx>) -> bool, |
| ) -> bool { |
| !self.any_free_region_meets(value, |r| !callback(r)) |
| } |
| |
| /// Returns `true` if `callback` returns true for some region appearing free in `value`. |
| pub fn any_free_region_meets( |
| self, |
| value: &impl TypeFoldable<'tcx>, |
| callback: impl FnMut(ty::Region<'tcx>) -> bool, |
| ) -> bool { |
| struct RegionVisitor<'tcx, F> { |
| tcx: TyCtxt<'tcx>, |
| /// The index of a binder *just outside* the things we have |
| /// traversed. If we encounter a bound region bound by this |
| /// binder or one outer to it, it appears free. Example: |
| /// |
| /// ``` |
| /// for<'a> fn(for<'b> fn(), T) |
| /// ^ ^ ^ ^ |
| /// | | | | here, would be shifted in 1 |
| /// | | | here, would be shifted in 2 |
| /// | | here, would be `INNERMOST` shifted in by 1 |
| /// | here, initially, binder would be `INNERMOST` |
| /// ``` |
| /// |
| /// You see that, initially, *any* bound value is free, |
| /// because we've not traversed any binders. As we pass |
| /// through a binder, we shift the `outer_index` by 1 to |
| /// account for the new binder that encloses us. |
| outer_index: ty::DebruijnIndex, |
| callback: F, |
| } |
| |
| impl<'tcx, F> TypeVisitor<'tcx> for RegionVisitor<'tcx, F> |
| where |
| F: FnMut(ty::Region<'tcx>) -> bool, |
| { |
| type BreakTy = (); |
| |
| fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> { |
| Some(self.tcx) |
| } |
| |
| fn visit_binder<T: TypeFoldable<'tcx>>( |
| &mut self, |
| t: &Binder<'tcx, T>, |
| ) -> ControlFlow<Self::BreakTy> { |
| self.outer_index.shift_in(1); |
| let result = t.as_ref().skip_binder().visit_with(self); |
| self.outer_index.shift_out(1); |
| result |
| } |
| |
| fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { |
| match *r { |
| ty::ReLateBound(debruijn, _) if debruijn < self.outer_index => { |
| ControlFlow::CONTINUE |
| } |
| _ => { |
| if (self.callback)(r) { |
| ControlFlow::BREAK |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| } |
| } |
| |
| fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| // We're only interested in types involving regions |
| if ty.flags().intersects(TypeFlags::HAS_POTENTIAL_FREE_REGIONS) { |
| ty.super_visit_with(self) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| } |
| |
| value |
| .visit_with(&mut RegionVisitor { tcx: self, outer_index: ty::INNERMOST, callback }) |
| .is_break() |
| } |
| } |
| |
| /// Folds over the substructure of a type, visiting its component |
| /// types and all regions that occur *free* within it. |
| /// |
| /// That is, `Ty` can contain function or method types that bind |
| /// regions at the call site (`ReLateBound`), and occurrences of |
| /// regions (aka "lifetimes") that are bound within a type are not |
| /// visited by this folder; only regions that occur free will be |
| /// visited by `fld_r`. |
| |
| pub struct RegionFolder<'a, 'tcx> { |
| tcx: TyCtxt<'tcx>, |
| skipped_regions: &'a mut bool, |
| |
| /// Stores the index of a binder *just outside* the stuff we have |
| /// visited. So this begins as INNERMOST; when we pass through a |
| /// binder, it is incremented (via `shift_in`). |
| current_index: ty::DebruijnIndex, |
| |
| /// Callback invokes for each free region. The `DebruijnIndex` |
| /// points to the binder *just outside* the ones we have passed |
| /// through. |
| fold_region_fn: |
| &'a mut (dyn FnMut(ty::Region<'tcx>, ty::DebruijnIndex) -> ty::Region<'tcx> + 'a), |
| } |
| |
| impl<'a, 'tcx> RegionFolder<'a, 'tcx> { |
| #[inline] |
| pub fn new( |
| tcx: TyCtxt<'tcx>, |
| skipped_regions: &'a mut bool, |
| fold_region_fn: &'a mut dyn FnMut(ty::Region<'tcx>, ty::DebruijnIndex) -> ty::Region<'tcx>, |
| ) -> RegionFolder<'a, 'tcx> { |
| RegionFolder { tcx, skipped_regions, current_index: ty::INNERMOST, fold_region_fn } |
| } |
| } |
| |
| impl<'a, 'tcx> TypeFolder<'tcx> for RegionFolder<'a, 'tcx> { |
| fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { |
| self.tcx |
| } |
| |
| fn fold_binder<T: TypeFoldable<'tcx>>( |
| &mut self, |
| t: ty::Binder<'tcx, T>, |
| ) -> ty::Binder<'tcx, T> { |
| self.current_index.shift_in(1); |
| let t = t.super_fold_with(self); |
| self.current_index.shift_out(1); |
| t |
| } |
| |
| #[instrument(skip(self), level = "debug")] |
| fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { |
| match *r { |
| ty::ReLateBound(debruijn, _) if debruijn < self.current_index => { |
| debug!(?self.current_index, "skipped bound region"); |
| *self.skipped_regions = true; |
| r |
| } |
| _ => { |
| debug!(?self.current_index, "folding free region"); |
| (self.fold_region_fn)(r, self.current_index) |
| } |
| } |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Bound vars replacer |
| |
| /// Replaces the escaping bound vars (late bound regions or bound types) in a type. |
| struct BoundVarReplacer<'a, 'tcx> { |
| tcx: TyCtxt<'tcx>, |
| |
| /// As with `RegionFolder`, represents the index of a binder *just outside* |
| /// the ones we have visited. |
| current_index: ty::DebruijnIndex, |
| |
| fld_r: Option<&'a mut (dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx> + 'a)>, |
| fld_t: Option<&'a mut (dyn FnMut(ty::BoundTy) -> Ty<'tcx> + 'a)>, |
| fld_c: Option<&'a mut (dyn FnMut(ty::BoundVar, Ty<'tcx>) -> &'tcx ty::Const<'tcx> + 'a)>, |
| } |
| |
| impl<'a, 'tcx> BoundVarReplacer<'a, 'tcx> { |
| fn new( |
| tcx: TyCtxt<'tcx>, |
| fld_r: Option<&'a mut (dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx> + 'a)>, |
| fld_t: Option<&'a mut (dyn FnMut(ty::BoundTy) -> Ty<'tcx> + 'a)>, |
| fld_c: Option<&'a mut (dyn FnMut(ty::BoundVar, Ty<'tcx>) -> &'tcx ty::Const<'tcx> + 'a)>, |
| ) -> Self { |
| BoundVarReplacer { tcx, current_index: ty::INNERMOST, fld_r, fld_t, fld_c } |
| } |
| } |
| |
| impl<'a, 'tcx> TypeFolder<'tcx> for BoundVarReplacer<'a, 'tcx> { |
| fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { |
| self.tcx |
| } |
| |
| fn fold_binder<T: TypeFoldable<'tcx>>( |
| &mut self, |
| t: ty::Binder<'tcx, T>, |
| ) -> ty::Binder<'tcx, T> { |
| self.current_index.shift_in(1); |
| let t = t.super_fold_with(self); |
| self.current_index.shift_out(1); |
| t |
| } |
| |
| fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { |
| match *t.kind() { |
| ty::Bound(debruijn, bound_ty) if debruijn == self.current_index => { |
| if let Some(fld_t) = self.fld_t.as_mut() { |
| let ty = fld_t(bound_ty); |
| return ty::fold::shift_vars(self.tcx, &ty, self.current_index.as_u32()); |
| } |
| } |
| _ if t.has_vars_bound_at_or_above(self.current_index) => { |
| return t.super_fold_with(self); |
| } |
| _ => {} |
| } |
| t |
| } |
| |
| fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { |
| match *r { |
| ty::ReLateBound(debruijn, br) if debruijn == self.current_index => { |
| if let Some(fld_r) = self.fld_r.as_mut() { |
| let region = fld_r(br); |
| return if let ty::ReLateBound(debruijn1, br) = *region { |
| // If the callback returns a late-bound region, |
| // that region should always use the INNERMOST |
| // debruijn index. Then we adjust it to the |
| // correct depth. |
| assert_eq!(debruijn1, ty::INNERMOST); |
| self.tcx.mk_region(ty::ReLateBound(debruijn, br)) |
| } else { |
| region |
| }; |
| } |
| } |
| _ => {} |
| } |
| r |
| } |
| |
| fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> { |
| match *ct { |
| ty::Const { val: ty::ConstKind::Bound(debruijn, bound_const), ty } |
| if debruijn == self.current_index => |
| { |
| if let Some(fld_c) = self.fld_c.as_mut() { |
| let ct = fld_c(bound_const, ty); |
| return ty::fold::shift_vars(self.tcx, &ct, self.current_index.as_u32()); |
| } |
| } |
| _ if ct.has_vars_bound_at_or_above(self.current_index) => { |
| return ct.super_fold_with(self); |
| } |
| _ => {} |
| } |
| ct |
| } |
| } |
| |
| impl<'tcx> TyCtxt<'tcx> { |
| /// Replaces all regions bound by the given `Binder` with the |
| /// results returned by the closure; the closure is expected to |
| /// return a free region (relative to this binder), and hence the |
| /// binder is removed in the return type. The closure is invoked |
| /// once for each unique `BoundRegionKind`; multiple references to the |
| /// same `BoundRegionKind` will reuse the previous result. A map is |
| /// returned at the end with each bound region and the free region |
| /// that replaced it. |
| /// |
| /// This method only replaces late bound regions and the result may still |
| /// contain escaping bound types. |
| pub fn replace_late_bound_regions<T, F>( |
| self, |
| value: Binder<'tcx, T>, |
| mut fld_r: F, |
| ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>) |
| where |
| F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>, |
| T: TypeFoldable<'tcx>, |
| { |
| let mut region_map = BTreeMap::new(); |
| let mut real_fld_r = |
| |br: ty::BoundRegion| *region_map.entry(br).or_insert_with(|| fld_r(br)); |
| let value = value.skip_binder(); |
| let value = if !value.has_escaping_bound_vars() { |
| value |
| } else { |
| let mut replacer = BoundVarReplacer::new(self, Some(&mut real_fld_r), None, None); |
| value.fold_with(&mut replacer) |
| }; |
| (value, region_map) |
| } |
| |
| /// Replaces all escaping bound vars. The `fld_r` closure replaces escaping |
| /// bound regions; the `fld_t` closure replaces escaping bound types and the `fld_c` |
| /// closure replaces escaping bound consts. |
| pub fn replace_escaping_bound_vars<T, F, G, H>( |
| self, |
| value: T, |
| mut fld_r: F, |
| mut fld_t: G, |
| mut fld_c: H, |
| ) -> T |
| where |
| F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>, |
| G: FnMut(ty::BoundTy) -> Ty<'tcx>, |
| H: FnMut(ty::BoundVar, Ty<'tcx>) -> &'tcx ty::Const<'tcx>, |
| T: TypeFoldable<'tcx>, |
| { |
| if !value.has_escaping_bound_vars() { |
| value |
| } else { |
| let mut replacer = |
| BoundVarReplacer::new(self, Some(&mut fld_r), Some(&mut fld_t), Some(&mut fld_c)); |
| value.fold_with(&mut replacer) |
| } |
| } |
| |
| /// Replaces all types or regions bound by the given `Binder`. The `fld_r` |
| /// closure replaces bound regions while the `fld_t` closure replaces bound |
| /// types. |
| pub fn replace_bound_vars<T, F, G, H>( |
| self, |
| value: Binder<'tcx, T>, |
| mut fld_r: F, |
| fld_t: G, |
| fld_c: H, |
| ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>) |
| where |
| F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>, |
| G: FnMut(ty::BoundTy) -> Ty<'tcx>, |
| H: FnMut(ty::BoundVar, Ty<'tcx>) -> &'tcx ty::Const<'tcx>, |
| T: TypeFoldable<'tcx>, |
| { |
| let mut region_map = BTreeMap::new(); |
| let real_fld_r = |br: ty::BoundRegion| *region_map.entry(br).or_insert_with(|| fld_r(br)); |
| let value = self.replace_escaping_bound_vars(value.skip_binder(), real_fld_r, fld_t, fld_c); |
| (value, region_map) |
| } |
| |
| /// Replaces any late-bound regions bound in `value` with |
| /// free variants attached to `all_outlive_scope`. |
| pub fn liberate_late_bound_regions<T>( |
| self, |
| all_outlive_scope: DefId, |
| value: ty::Binder<'tcx, T>, |
| ) -> T |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| self.replace_late_bound_regions(value, |br| { |
| self.mk_region(ty::ReFree(ty::FreeRegion { |
| scope: all_outlive_scope, |
| bound_region: br.kind, |
| })) |
| }) |
| .0 |
| } |
| |
| pub fn shift_bound_var_indices<T>(self, bound_vars: usize, value: T) -> T |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| self.replace_escaping_bound_vars( |
| value, |
| |r| { |
| self.mk_region(ty::ReLateBound( |
| ty::INNERMOST, |
| ty::BoundRegion { |
| var: ty::BoundVar::from_usize(r.var.as_usize() + bound_vars), |
| kind: r.kind, |
| }, |
| )) |
| }, |
| |t| { |
| self.mk_ty(ty::Bound( |
| ty::INNERMOST, |
| ty::BoundTy { |
| var: ty::BoundVar::from_usize(t.var.as_usize() + bound_vars), |
| kind: t.kind, |
| }, |
| )) |
| }, |
| |c, ty| { |
| self.mk_const(ty::Const { |
| val: ty::ConstKind::Bound( |
| ty::INNERMOST, |
| ty::BoundVar::from_usize(c.as_usize() + bound_vars), |
| ), |
| ty, |
| }) |
| }, |
| ) |
| } |
| |
| /// Returns a set of all late-bound regions that are constrained |
| /// by `value`, meaning that if we instantiate those LBR with |
| /// variables and equate `value` with something else, those |
| /// variables will also be equated. |
| pub fn collect_constrained_late_bound_regions<T>( |
| self, |
| value: &Binder<'tcx, T>, |
| ) -> FxHashSet<ty::BoundRegionKind> |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| self.collect_late_bound_regions(value, true) |
| } |
| |
| /// Returns a set of all late-bound regions that appear in `value` anywhere. |
| pub fn collect_referenced_late_bound_regions<T>( |
| self, |
| value: &Binder<'tcx, T>, |
| ) -> FxHashSet<ty::BoundRegionKind> |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| self.collect_late_bound_regions(value, false) |
| } |
| |
| fn collect_late_bound_regions<T>( |
| self, |
| value: &Binder<'tcx, T>, |
| just_constraint: bool, |
| ) -> FxHashSet<ty::BoundRegionKind> |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| let mut collector = LateBoundRegionsCollector::new(self, just_constraint); |
| let result = value.as_ref().skip_binder().visit_with(&mut collector); |
| assert!(result.is_continue()); // should never have stopped early |
| collector.regions |
| } |
| |
| /// Replaces any late-bound regions bound in `value` with `'erased`. Useful in codegen but also |
| /// method lookup and a few other places where precise region relationships are not required. |
| pub fn erase_late_bound_regions<T>(self, value: Binder<'tcx, T>) -> T |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| self.replace_late_bound_regions(value, |_| self.lifetimes.re_erased).0 |
| } |
| |
| /// Rewrite any late-bound regions so that they are anonymous. Region numbers are |
| /// assigned starting at 0 and increasing monotonically in the order traversed |
| /// by the fold operation. |
| /// |
| /// The chief purpose of this function is to canonicalize regions so that two |
| /// `FnSig`s or `TraitRef`s which are equivalent up to region naming will become |
| /// structurally identical. For example, `for<'a, 'b> fn(&'a isize, &'b isize)` and |
| /// `for<'a, 'b> fn(&'b isize, &'a isize)` will become identical after anonymization. |
| pub fn anonymize_late_bound_regions<T>(self, sig: Binder<'tcx, T>) -> Binder<'tcx, T> |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| let mut counter = 0; |
| let inner = self |
| .replace_late_bound_regions(sig, |_| { |
| let br = ty::BoundRegion { |
| var: ty::BoundVar::from_u32(counter), |
| kind: ty::BrAnon(counter), |
| }; |
| let r = self.mk_region(ty::ReLateBound(ty::INNERMOST, br)); |
| counter += 1; |
| r |
| }) |
| .0; |
| let bound_vars = self.mk_bound_variable_kinds( |
| (0..counter).map(|i| ty::BoundVariableKind::Region(ty::BrAnon(i))), |
| ); |
| Binder::bind_with_vars(inner, bound_vars) |
| } |
| } |
| |
| pub struct ValidateBoundVars<'tcx> { |
| bound_vars: &'tcx ty::List<ty::BoundVariableKind>, |
| binder_index: ty::DebruijnIndex, |
| // We may encounter the same variable at different levels of binding, so |
| // this can't just be `Ty` |
| visited: SsoHashSet<(ty::DebruijnIndex, Ty<'tcx>)>, |
| } |
| |
| impl<'tcx> ValidateBoundVars<'tcx> { |
| pub fn new(bound_vars: &'tcx ty::List<ty::BoundVariableKind>) -> Self { |
| ValidateBoundVars { |
| bound_vars, |
| binder_index: ty::INNERMOST, |
| visited: SsoHashSet::default(), |
| } |
| } |
| } |
| |
| impl<'tcx> TypeVisitor<'tcx> for ValidateBoundVars<'tcx> { |
| type BreakTy = (); |
| |
| fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> { |
| // Anonymous constants do not contain bound vars in their substs by default. |
| None |
| } |
| |
| fn visit_binder<T: TypeFoldable<'tcx>>( |
| &mut self, |
| t: &Binder<'tcx, T>, |
| ) -> ControlFlow<Self::BreakTy> { |
| self.binder_index.shift_in(1); |
| let result = t.super_visit_with(self); |
| self.binder_index.shift_out(1); |
| result |
| } |
| |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if t.outer_exclusive_binder < self.binder_index |
| || !self.visited.insert((self.binder_index, t)) |
| { |
| return ControlFlow::BREAK; |
| } |
| match *t.kind() { |
| ty::Bound(debruijn, bound_ty) if debruijn == self.binder_index => { |
| if self.bound_vars.len() <= bound_ty.var.as_usize() { |
| bug!("Not enough bound vars: {:?} not found in {:?}", t, self.bound_vars); |
| } |
| let list_var = self.bound_vars[bound_ty.var.as_usize()]; |
| match list_var { |
| ty::BoundVariableKind::Ty(kind) => { |
| if kind != bound_ty.kind { |
| bug!( |
| "Mismatched type kinds: {:?} doesn't var in list {:?}", |
| bound_ty.kind, |
| list_var |
| ); |
| } |
| } |
| _ => { |
| bug!("Mismatched bound variable kinds! Expected type, found {:?}", list_var) |
| } |
| } |
| } |
| |
| _ => (), |
| }; |
| |
| t.super_visit_with(self) |
| } |
| |
| fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { |
| match r { |
| ty::ReLateBound(index, br) if *index == self.binder_index => { |
| if self.bound_vars.len() <= br.var.as_usize() { |
| bug!("Not enough bound vars: {:?} not found in {:?}", *br, self.bound_vars); |
| } |
| let list_var = self.bound_vars[br.var.as_usize()]; |
| match list_var { |
| ty::BoundVariableKind::Region(kind) => { |
| if kind != br.kind { |
| bug!( |
| "Mismatched region kinds: {:?} doesn't match var ({:?}) in list ({:?})", |
| br.kind, |
| list_var, |
| self.bound_vars |
| ); |
| } |
| } |
| _ => bug!( |
| "Mismatched bound variable kinds! Expected region, found {:?}", |
| list_var |
| ), |
| } |
| } |
| |
| _ => (), |
| }; |
| |
| r.super_visit_with(self) |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Shifter |
| // |
| // Shifts the De Bruijn indices on all escaping bound vars by a |
| // fixed amount. Useful in substitution or when otherwise introducing |
| // a binding level that is not intended to capture the existing bound |
| // vars. See comment on `shift_vars_through_binders` method in |
| // `subst.rs` for more details. |
| |
| struct Shifter<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| current_index: ty::DebruijnIndex, |
| amount: u32, |
| } |
| |
| impl<'tcx> Shifter<'tcx> { |
| pub fn new(tcx: TyCtxt<'tcx>, amount: u32) -> Self { |
| Shifter { tcx, current_index: ty::INNERMOST, amount } |
| } |
| } |
| |
| impl<'tcx> TypeFolder<'tcx> for Shifter<'tcx> { |
| fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { |
| self.tcx |
| } |
| |
| fn fold_binder<T: TypeFoldable<'tcx>>( |
| &mut self, |
| t: ty::Binder<'tcx, T>, |
| ) -> ty::Binder<'tcx, T> { |
| self.current_index.shift_in(1); |
| let t = t.super_fold_with(self); |
| self.current_index.shift_out(1); |
| t |
| } |
| |
| fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { |
| match *r { |
| ty::ReLateBound(debruijn, br) => { |
| if self.amount == 0 || debruijn < self.current_index { |
| r |
| } else { |
| let debruijn = debruijn.shifted_in(self.amount); |
| let shifted = ty::ReLateBound(debruijn, br); |
| self.tcx.mk_region(shifted) |
| } |
| } |
| _ => r, |
| } |
| } |
| |
| fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { |
| match *ty.kind() { |
| ty::Bound(debruijn, bound_ty) => { |
| if self.amount == 0 || debruijn < self.current_index { |
| ty |
| } else { |
| let debruijn = debruijn.shifted_in(self.amount); |
| self.tcx.mk_ty(ty::Bound(debruijn, bound_ty)) |
| } |
| } |
| |
| _ => ty.super_fold_with(self), |
| } |
| } |
| |
| fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> { |
| if let ty::Const { val: ty::ConstKind::Bound(debruijn, bound_ct), ty } = *ct { |
| if self.amount == 0 || debruijn < self.current_index { |
| ct |
| } else { |
| let debruijn = debruijn.shifted_in(self.amount); |
| self.tcx.mk_const(ty::Const { val: ty::ConstKind::Bound(debruijn, bound_ct), ty }) |
| } |
| } else { |
| ct.super_fold_with(self) |
| } |
| } |
| } |
| |
| pub fn shift_region<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| region: ty::Region<'tcx>, |
| amount: u32, |
| ) -> ty::Region<'tcx> { |
| match region { |
| ty::ReLateBound(debruijn, br) if amount > 0 => { |
| tcx.mk_region(ty::ReLateBound(debruijn.shifted_in(amount), *br)) |
| } |
| _ => region, |
| } |
| } |
| |
| pub fn shift_vars<'tcx, T>(tcx: TyCtxt<'tcx>, value: T, amount: u32) -> T |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| debug!("shift_vars(value={:?}, amount={})", value, amount); |
| |
| value.fold_with(&mut Shifter::new(tcx, amount)) |
| } |
| |
| #[derive(Debug, PartialEq, Eq, Copy, Clone)] |
| struct FoundEscapingVars; |
| |
| /// An "escaping var" is a bound var whose binder is not part of `t`. A bound var can be a |
| /// bound region or a bound type. |
| /// |
| /// So, for example, consider a type like the following, which has two binders: |
| /// |
| /// for<'a> fn(x: for<'b> fn(&'a isize, &'b isize)) |
| /// ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ outer scope |
| /// ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ inner scope |
| /// |
| /// This type has *bound regions* (`'a`, `'b`), but it does not have escaping regions, because the |
| /// binders of both `'a` and `'b` are part of the type itself. However, if we consider the *inner |
| /// fn type*, that type has an escaping region: `'a`. |
| /// |
| /// Note that what I'm calling an "escaping var" is often just called a "free var". However, |
| /// we already use the term "free var". It refers to the regions or types that we use to represent |
| /// bound regions or type params on a fn definition while we are type checking its body. |
| /// |
| /// To clarify, conceptually there is no particular difference between |
| /// an "escaping" var and a "free" var. However, there is a big |
| /// difference in practice. Basically, when "entering" a binding |
| /// level, one is generally required to do some sort of processing to |
| /// a bound var, such as replacing it with a fresh/placeholder |
| /// var, or making an entry in the environment to represent the |
| /// scope to which it is attached, etc. An escaping var represents |
| /// a bound var for which this processing has not yet been done. |
| struct HasEscapingVarsVisitor { |
| /// Anything bound by `outer_index` or "above" is escaping. |
| outer_index: ty::DebruijnIndex, |
| } |
| |
| impl<'tcx> TypeVisitor<'tcx> for HasEscapingVarsVisitor { |
| type BreakTy = FoundEscapingVars; |
| |
| fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> { |
| // Anonymous constants do not contain bound vars in their substs by default. |
| None |
| } |
| |
| fn visit_binder<T: TypeFoldable<'tcx>>( |
| &mut self, |
| t: &Binder<'tcx, T>, |
| ) -> ControlFlow<Self::BreakTy> { |
| self.outer_index.shift_in(1); |
| let result = t.super_visit_with(self); |
| self.outer_index.shift_out(1); |
| result |
| } |
| |
| #[inline] |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| // If the outer-exclusive-binder is *strictly greater* than |
| // `outer_index`, that means that `t` contains some content |
| // bound at `outer_index` or above (because |
| // `outer_exclusive_binder` is always 1 higher than the |
| // content in `t`). Therefore, `t` has some escaping vars. |
| if t.outer_exclusive_binder > self.outer_index { |
| ControlFlow::Break(FoundEscapingVars) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| |
| #[inline] |
| fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { |
| // If the region is bound by `outer_index` or anything outside |
| // of outer index, then it escapes the binders we have |
| // visited. |
| if r.bound_at_or_above_binder(self.outer_index) { |
| ControlFlow::Break(FoundEscapingVars) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| |
| fn visit_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> { |
| // we don't have a `visit_infer_const` callback, so we have to |
| // hook in here to catch this case (annoying...), but |
| // otherwise we do want to remember to visit the rest of the |
| // const, as it has types/regions embedded in a lot of other |
| // places. |
| match ct.val { |
| ty::ConstKind::Bound(debruijn, _) if debruijn >= self.outer_index => { |
| ControlFlow::Break(FoundEscapingVars) |
| } |
| _ => ct.super_visit_with(self), |
| } |
| } |
| |
| #[inline] |
| fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if predicate.inner.outer_exclusive_binder > self.outer_index { |
| ControlFlow::Break(FoundEscapingVars) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| } |
| |
| #[derive(Debug, PartialEq, Eq, Copy, Clone)] |
| struct FoundFlags; |
| |
| // FIXME: Optimize for checking for infer flags |
| struct HasTypeFlagsVisitor<'tcx> { |
| tcx: Option<TyCtxt<'tcx>>, |
| flags: ty::TypeFlags, |
| } |
| |
| impl<'tcx> std::fmt::Debug for HasTypeFlagsVisitor<'tcx> { |
| fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { |
| self.flags.fmt(fmt) |
| } |
| } |
| |
| impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor<'tcx> { |
| type BreakTy = FoundFlags; |
| fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> { |
| bug!("we shouldn't call this method as we manually look at ct substs"); |
| } |
| |
| #[inline] |
| #[instrument(level = "trace")] |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| let flags = t.flags(); |
| trace!(t.flags=?t.flags()); |
| if flags.intersects(self.flags) { |
| ControlFlow::Break(FoundFlags) |
| } else { |
| match flags.intersects(TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS) { |
| true if self.tcx.is_some() => UnknownConstSubstsVisitor::search(&self, t), |
| _ => ControlFlow::CONTINUE, |
| } |
| } |
| } |
| |
| #[inline] |
| #[instrument(skip(self), level = "trace")] |
| fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { |
| let flags = r.type_flags(); |
| trace!(r.flags=?flags); |
| if flags.intersects(self.flags) { |
| ControlFlow::Break(FoundFlags) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| |
| #[inline] |
| #[instrument(level = "trace")] |
| fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> { |
| let flags = FlagComputation::for_const(c); |
| trace!(r.flags=?flags); |
| if flags.intersects(self.flags) { |
| ControlFlow::Break(FoundFlags) |
| } else { |
| match flags.intersects(TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS) { |
| true if self.tcx.is_some() => UnknownConstSubstsVisitor::search(&self, c), |
| _ => ControlFlow::CONTINUE, |
| } |
| } |
| } |
| |
| #[inline] |
| #[instrument(level = "trace")] |
| fn visit_unevaluated_const(&mut self, uv: ty::Unevaluated<'tcx>) -> ControlFlow<Self::BreakTy> { |
| let flags = FlagComputation::for_unevaluated_const(uv); |
| trace!(r.flags=?flags); |
| if flags.intersects(self.flags) { |
| ControlFlow::Break(FoundFlags) |
| } else { |
| match flags.intersects(TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS) { |
| true if self.tcx.is_some() => UnknownConstSubstsVisitor::search(&self, uv), |
| _ => ControlFlow::CONTINUE, |
| } |
| } |
| } |
| |
| #[inline] |
| #[instrument(level = "trace")] |
| fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> { |
| let flags = predicate.inner.flags; |
| trace!(predicate.flags=?flags); |
| if flags.intersects(self.flags) { |
| ControlFlow::Break(FoundFlags) |
| } else { |
| match flags.intersects(TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS) { |
| true if self.tcx.is_some() => UnknownConstSubstsVisitor::search(&self, predicate), |
| _ => ControlFlow::CONTINUE, |
| } |
| } |
| } |
| } |
| |
| struct UnknownConstSubstsVisitor<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| flags: ty::TypeFlags, |
| } |
| |
| impl<'tcx> UnknownConstSubstsVisitor<'tcx> { |
| /// This is fairly cold and we don't want to |
| /// bloat the size of the `HasTypeFlagsVisitor`. |
| #[inline(never)] |
| pub fn search<T: TypeFoldable<'tcx>>( |
| visitor: &HasTypeFlagsVisitor<'tcx>, |
| v: T, |
| ) -> ControlFlow<FoundFlags> { |
| if visitor.flags.intersects(TypeFlags::MAY_NEED_DEFAULT_CONST_SUBSTS) { |
| v.super_visit_with(&mut UnknownConstSubstsVisitor { |
| tcx: visitor.tcx.unwrap(), |
| flags: visitor.flags, |
| }) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| } |
| |
| impl<'tcx> TypeVisitor<'tcx> for UnknownConstSubstsVisitor<'tcx> { |
| type BreakTy = FoundFlags; |
| fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> { |
| bug!("we shouldn't call this method as we manually look at ct substs"); |
| } |
| |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if t.flags().intersects(TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS) { |
| t.super_visit_with(self) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| |
| #[inline] |
| fn visit_unevaluated_const(&mut self, uv: ty::Unevaluated<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if uv.substs_.is_none() { |
| self.tcx |
| .default_anon_const_substs(uv.def.did) |
| .visit_with(&mut HasTypeFlagsVisitor { tcx: Some(self.tcx), flags: self.flags }) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| |
| #[inline] |
| fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if predicate.inner.flags.intersects(TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS) { |
| predicate.super_visit_with(self) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| } |
| |
| impl<'tcx> TyCtxt<'tcx> { |
| /// This is a HACK(const_generics) and should probably not be needed. |
| /// Might however be perf relevant, so who knows. |
| /// |
| /// FIXME(@lcnr): explain this function a bit more |
| pub fn expose_default_const_substs<T: TypeFoldable<'tcx>>(self, v: T) -> T { |
| v.fold_with(&mut ExposeDefaultConstSubstsFolder { tcx: self }) |
| } |
| } |
| |
| struct ExposeDefaultConstSubstsFolder<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| } |
| |
| impl<'tcx> TypeFolder<'tcx> for ExposeDefaultConstSubstsFolder<'tcx> { |
| fn tcx(&self) -> TyCtxt<'tcx> { |
| self.tcx |
| } |
| |
| fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { |
| if ty.flags().intersects(TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS) { |
| ty.super_fold_with(self) |
| } else { |
| ty |
| } |
| } |
| |
| fn fold_predicate(&mut self, pred: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> { |
| if pred.inner.flags.intersects(TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS) { |
| pred.super_fold_with(self) |
| } else { |
| pred |
| } |
| } |
| } |
| |
| /// Collects all the late-bound regions at the innermost binding level |
| /// into a hash set. |
| struct LateBoundRegionsCollector<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| current_index: ty::DebruijnIndex, |
| regions: FxHashSet<ty::BoundRegionKind>, |
| |
| /// `true` if we only want regions that are known to be |
| /// "constrained" when you equate this type with another type. In |
| /// particular, if you have e.g., `&'a u32` and `&'b u32`, equating |
| /// them constraints `'a == 'b`. But if you have `<&'a u32 as |
| /// Trait>::Foo` and `<&'b u32 as Trait>::Foo`, normalizing those |
| /// types may mean that `'a` and `'b` don't appear in the results, |
| /// so they are not considered *constrained*. |
| just_constrained: bool, |
| } |
| |
| impl<'tcx> LateBoundRegionsCollector<'tcx> { |
| fn new(tcx: TyCtxt<'tcx>, just_constrained: bool) -> Self { |
| LateBoundRegionsCollector { |
| tcx, |
| current_index: ty::INNERMOST, |
| regions: Default::default(), |
| just_constrained, |
| } |
| } |
| } |
| |
| impl<'tcx> TypeVisitor<'tcx> for LateBoundRegionsCollector<'tcx> { |
| fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> { |
| Some(self.tcx) |
| } |
| |
| fn visit_binder<T: TypeFoldable<'tcx>>( |
| &mut self, |
| t: &Binder<'tcx, T>, |
| ) -> ControlFlow<Self::BreakTy> { |
| self.current_index.shift_in(1); |
| let result = t.super_visit_with(self); |
| self.current_index.shift_out(1); |
| result |
| } |
| |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| // if we are only looking for "constrained" region, we have to |
| // ignore the inputs to a projection, as they may not appear |
| // in the normalized form |
| if self.just_constrained { |
| if let ty::Projection(..) | ty::Opaque(..) = t.kind() { |
| return ControlFlow::CONTINUE; |
| } |
| } |
| |
| t.super_visit_with(self) |
| } |
| |
| fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> { |
| // if we are only looking for "constrained" region, we have to |
| // ignore the inputs of an unevaluated const, as they may not appear |
| // in the normalized form |
| if self.just_constrained { |
| if let ty::ConstKind::Unevaluated(..) = c.val { |
| return ControlFlow::CONTINUE; |
| } |
| } |
| |
| c.super_visit_with(self) |
| } |
| |
| fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if let ty::ReLateBound(debruijn, br) = *r { |
| if debruijn == self.current_index { |
| self.regions.insert(br.kind); |
| } |
| } |
| ControlFlow::CONTINUE |
| } |
| } |
