| //! A visiting traversal mechanism for complex data structures that contain type |
| //! information. |
| //! |
| //! This is a read-only traversal of the data structure. |
| //! |
| //! This traversal has limited flexibility. Only a small number of "types of |
| //! interest" within the complex data structures can receive custom |
| //! visitation. These are the ones containing the most important type-related |
| //! information, such as `Ty`, `Predicate`, `Region`, and `Const`. |
| //! |
| //! There are three groups of traits involved in each traversal. |
| //! - `TypeVisitable`. This is implemented once for many types, including: |
| //! - Types of interest, for which the methods delegate to the visitor. |
| //! - All other types, including generic containers like `Vec` and `Option`. |
| //! It defines a "skeleton" of how they should be visited. |
| //! - `TypeSuperVisitable`. This is implemented only for each type of interest, |
| //! and defines the visiting "skeleton" for these types. |
| //! - `TypeVisitor`. This is implemented for each visitor. This defines how |
| //! types of interest are visited. |
| //! |
| //! This means each visit is a mixture of (a) generic visiting operations, and (b) |
| //! custom visit operations that are specific to the visitor. |
| //! - The `TypeVisitable` impls handle most of the traversal, and call into |
| //! `TypeVisitor` when they encounter a type of interest. |
| //! - A `TypeVisitor` may call into another `TypeVisitable` impl, because some of |
| //! the types of interest are recursive and can contain other types of interest. |
| //! - A `TypeVisitor` may also call into a `TypeSuperVisitable` impl, because each |
| //! visitor might provide custom handling only for some types of interest, or |
| //! only for some variants of each type of interest, and then use default |
| //! traversal for the remaining cases. |
| //! |
| //! For example, if you have `struct S(Ty, U)` where `S: TypeVisitable` and `U: |
| //! TypeVisitable`, and an instance `s = S(ty, u)`, it would be visited like so: |
| //! ```text |
| //! s.visit_with(visitor) calls |
| //! - ty.visit_with(visitor) calls |
| //! - visitor.visit_ty(ty) may call |
| //! - ty.super_visit_with(visitor) |
| //! - u.visit_with(visitor) |
| //! ``` |
| use crate::ty::{self, flags::FlagComputation, Binder, Ty, TyCtxt, TypeFlags}; |
| use rustc_errors::ErrorGuaranteed; |
| |
| use rustc_data_structures::fx::FxHashSet; |
| use rustc_data_structures::sso::SsoHashSet; |
| use std::fmt; |
| use std::ops::ControlFlow; |
| |
| /// This trait is implemented for every type that can be visited, |
| /// providing the skeleton of the traversal. |
| /// |
| /// To implement this conveniently, use the derive macro located in |
| /// `rustc_macros`. |
| pub trait TypeVisitable<'tcx>: fmt::Debug + Clone { |
| /// The entry point for visiting. To visit a value `t` with a visitor `v` |
| /// call: `t.visit_with(v)`. |
| /// |
| /// For most types, this just traverses the value, calling `visit_with` on |
| /// each field/element. |
| /// |
| /// For types of interest (such as `Ty`), the implementation of this method |
| /// that calls a visitor method specifically for that type (such as |
| /// `V::visit_ty`). This is where control transfers from `TypeFoldable` to |
| /// `TypeVisitor`. |
| fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy>; |
| |
| /// 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) |
| } |
| |
| #[instrument(level = "trace", ret)] |
| fn has_type_flags(&self, flags: TypeFlags) -> bool { |
| self.visit_with(&mut HasTypeFlagsVisitor { 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 error_reported(&self) -> Option<ErrorGuaranteed> { |
| if self.references_error() { |
| Some(ErrorGuaranteed::unchecked_claim_error_was_emitted()) |
| } else { |
| None |
| } |
| } |
| fn has_non_region_param(&self) -> bool { |
| self.has_type_flags(TypeFlags::NEEDS_SUBST - TypeFlags::HAS_RE_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_non_region_infer(&self) -> bool { |
| self.has_type_flags(TypeFlags::NEEDS_INFER - TypeFlags::HAS_RE_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 needs_subst(&self) -> bool { |
| self.has_type_flags(TypeFlags::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) -> bool { |
| self.has_type_flags(TypeFlags::HAS_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) -> bool { |
| self.has_type_flags(TypeFlags::HAS_FREE_REGIONS) |
| } |
| |
| /// 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) -> bool { |
| !self.has_type_flags(TypeFlags::HAS_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) |
| } |
| } |
| |
| pub trait TypeSuperVisitable<'tcx>: TypeVisitable<'tcx> { |
| /// Provides a default visit for a type of interest. This should only be |
| /// called within `TypeVisitor` methods, when a non-custom traversal is |
| /// desired for the value of the type of interest passed to that method. |
| /// For example, in `MyVisitor::visit_ty(ty)`, it is valid to call |
| /// `ty.super_visit_with(self)`, but any other visiting should be done |
| /// with `xyz.visit_with(self)`. |
| fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy>; |
| } |
| |
| /// This trait is implemented for every visiting traversal. There is a visit |
| /// method defined for every type of interest. Each such method has a default |
| /// that recurses into the type's fields in a non-custom fashion. |
| pub trait TypeVisitor<'tcx>: Sized { |
| type BreakTy = !; |
| |
| fn visit_binder<T: TypeVisitable<'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: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> { |
| c.super_visit_with(self) |
| } |
| |
| fn visit_predicate(&mut self, p: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> { |
| p.super_visit_with(self) |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Region folder |
| |
| impl<'tcx> TyCtxt<'tcx> { |
| /// Invoke `callback` on every region appearing free in `value`. |
| pub fn for_each_free_region( |
| self, |
| value: &impl TypeVisitable<'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 TypeVisitable<'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 TypeVisitable<'tcx>, |
| callback: impl FnMut(ty::Region<'tcx>) -> bool, |
| ) -> bool { |
| struct RegionVisitor<F> { |
| /// 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: |
| /// |
| /// ```ignore (illustrative) |
| /// 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<F> |
| where |
| F: FnMut(ty::Region<'tcx>) -> bool, |
| { |
| type BreakTy = (); |
| |
| fn visit_binder<T: TypeVisitable<'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 |
| } |
| |
| 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_FREE_REGIONS) { |
| ty.super_visit_with(self) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| } |
| |
| value.visit_with(&mut RegionVisitor { outer_index: ty::INNERMOST, callback }).is_break() |
| } |
| |
| /// 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: TypeVisitable<'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: TypeVisitable<'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: TypeVisitable<'tcx>, |
| { |
| let mut collector = LateBoundRegionsCollector::new(just_constraint); |
| let result = value.as_ref().skip_binder().visit_with(&mut collector); |
| assert!(result.is_continue()); // should never have stopped early |
| collector.regions |
| } |
| } |
| |
| 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 visit_binder<T: TypeVisitable<'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) |
| } |
| } |
| |
| #[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 visit_binder<T: TypeVisitable<'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: 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.kind() { |
| 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.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 { |
| flags: ty::TypeFlags, |
| } |
| |
| impl std::fmt::Debug for HasTypeFlagsVisitor { |
| fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { |
| self.flags.fmt(fmt) |
| } |
| } |
| |
| impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor { |
| type BreakTy = FoundFlags; |
| |
| #[inline] |
| #[instrument(skip(self), level = "trace", ret)] |
| 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 { |
| ControlFlow::CONTINUE |
| } |
| } |
| |
| #[inline] |
| #[instrument(skip(self), level = "trace", ret)] |
| 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", ret)] |
| fn visit_const(&mut self, c: 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 { |
| ControlFlow::CONTINUE |
| } |
| } |
| |
| #[inline] |
| #[instrument(level = "trace", ret)] |
| fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> { |
| debug!( |
| "HasTypeFlagsVisitor: predicate={:?} predicate.flags={:?} self.flags={:?}", |
| predicate, |
| predicate.flags(), |
| self.flags |
| ); |
| if predicate.flags().intersects(self.flags) { |
| ControlFlow::Break(FoundFlags) |
| } else { |
| ControlFlow::CONTINUE |
| } |
| } |
| } |
| |
| /// Collects all the late-bound regions at the innermost binding level |
| /// into a hash set. |
| struct LateBoundRegionsCollector { |
| 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 LateBoundRegionsCollector { |
| fn new(just_constrained: bool) -> Self { |
| LateBoundRegionsCollector { |
| current_index: ty::INNERMOST, |
| regions: Default::default(), |
| just_constrained, |
| } |
| } |
| } |
| |
| impl<'tcx> TypeVisitor<'tcx> for LateBoundRegionsCollector { |
| fn visit_binder<T: TypeVisitable<'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: 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.kind() { |
| 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 |
| } |
| } |
| |
| /// Finds the max universe present |
| pub struct MaxUniverse { |
| max_universe: ty::UniverseIndex, |
| } |
| |
| impl MaxUniverse { |
| pub fn new() -> Self { |
| MaxUniverse { max_universe: ty::UniverseIndex::ROOT } |
| } |
| |
| pub fn max_universe(self) -> ty::UniverseIndex { |
| self.max_universe |
| } |
| } |
| |
| impl<'tcx> TypeVisitor<'tcx> for MaxUniverse { |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if let ty::Placeholder(placeholder) = t.kind() { |
| self.max_universe = ty::UniverseIndex::from_u32( |
| self.max_universe.as_u32().max(placeholder.universe.as_u32()), |
| ); |
| } |
| |
| t.super_visit_with(self) |
| } |
| |
| fn visit_const(&mut self, c: ty::consts::Const<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if let ty::ConstKind::Placeholder(placeholder) = c.kind() { |
| self.max_universe = ty::UniverseIndex::from_u32( |
| self.max_universe.as_u32().max(placeholder.universe.as_u32()), |
| ); |
| } |
| |
| c.super_visit_with(self) |
| } |
| |
| fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if let ty::RePlaceholder(placeholder) = *r { |
| self.max_universe = ty::UniverseIndex::from_u32( |
| self.max_universe.as_u32().max(placeholder.universe.as_u32()), |
| ); |
| } |
| |
| ControlFlow::CONTINUE |
| } |
| } |
