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Diffstat (limited to 'compiler/rustc_middle/src/ty/visit.rs')
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1 files changed, 745 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/visit.rs b/compiler/rustc_middle/src/ty/visit.rs new file mode 100644 index 000000000..536506720 --- /dev/null +++ b/compiler/rustc_middle/src/ty/visit.rs @@ -0,0 +1,745 @@ +//! 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 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::mir; +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")] + 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_param_types_or_consts(&self) -> bool { + self.has_type_flags(TypeFlags::HAS_TY_PARAM | TypeFlags::HAS_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 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_unevaluated(&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) + } + + fn visit_mir_const(&mut self, c: mir::ConstantKind<'tcx>) -> ControlFlow<Self::BreakTy> { + c.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")] + 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")] + 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: 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")] + fn visit_unevaluated(&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 { + ControlFlow::CONTINUE + } + } + + #[inline] + #[instrument(level = "trace")] + 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(..) = 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 + } +} |