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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::ops::ControlFlow;
pub use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
pub trait TypeVisitableExt<'tcx>: TypeVisitable<TyCtxt<'tcx>> {
/// 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 type 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))
}
/// Return `true` if this type has regions that are not a part of the type.
/// For example, `for<'a> fn(&'a i32)` return `false`, while `fn(&'a i32)`
/// would return `true`. The latter can occur when traversing through the
/// former.
///
/// See [`HasEscapingVarsVisitor`] for more information.
fn has_escaping_bound_vars(&self) -> bool {
self.has_vars_bound_at_or_above(ty::INNERMOST)
}
fn has_type_flags(&self, flags: TypeFlags) -> bool {
let res =
self.visit_with(&mut HasTypeFlagsVisitor { flags }).break_value() == Some(FoundFlags);
trace!(?self, ?flags, ?res, "has_type_flags");
res
}
fn has_projections(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_PROJECTION)
}
fn has_inherent_projections(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_TY_INHERENT)
}
fn has_opaque_types(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_TY_OPAQUE)
}
fn has_generators(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_TY_GENERATOR)
}
fn references_error(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_ERROR)
}
fn error_reported(&self) -> Result<(), ErrorGuaranteed> {
if self.references_error() {
if let Some(reported) = ty::tls::with(|tcx| tcx.sess.is_compilation_going_to_fail()) {
Err(reported)
} else {
bug!("expect tcx.sess.is_compilation_going_to_fail return `Some`");
}
} else {
Ok(())
}
}
fn has_non_region_param(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_PARAM - 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::HAS_INFER - TypeFlags::HAS_RE_INFER)
}
fn has_infer(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_INFER)
}
fn has_placeholders(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_PLACEHOLDER)
}
fn has_non_region_placeholders(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_PLACEHOLDER - TypeFlags::HAS_RE_PLACEHOLDER)
}
fn has_param(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_PARAM)
}
/// "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)
}
/// True if there are any late-bound non-region variables
fn has_non_region_late_bound(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_LATE_BOUND - TypeFlags::HAS_RE_LATE_BOUND)
}
/// True if there are any late-bound variables
fn has_late_bound_vars(&self) -> bool {
self.has_type_flags(TypeFlags::HAS_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, T: TypeVisitable<TyCtxt<'tcx>>> TypeVisitableExt<'tcx> for T {}
///////////////////////////////////////////////////////////////////////////
// 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<TyCtxt<'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<TyCtxt<'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<TyCtxt<'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<TyCtxt<'tcx>> for RegionVisitor<F>
where
F: FnMut(ty::Region<'tcx>) -> bool,
{
type BreakTy = ();
fn visit_binder<T: TypeVisitable<TyCtxt<'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<TyCtxt<'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<TyCtxt<'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<TyCtxt<'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<TyCtxt<'tcx>> for ValidateBoundVars<'tcx> {
type BreakTy = ();
fn visit_binder<T: TypeVisitable<TyCtxt<'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
),
}
}
_ => (),
};
ControlFlow::Continue(())
}
}
#[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<TyCtxt<'tcx>> for HasEscapingVarsVisitor {
type BreakTy = FoundEscapingVars;
fn visit_binder<T: TypeVisitable<TyCtxt<'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)
}
}
// Note: this visitor traverses values down to the level of
// `Ty`/`Const`/`Predicate`, but not within those types. This is because the
// type flags at the outer layer are enough. So it's faster than it first
// looks, particular for `Ty`/`Predicate` where it's just a field access.
//
// N.B. The only case where this isn't totally true is binders, which also
// add `HAS_{RE,TY,CT}_LATE_BOUND` flag depending on the *bound variables* that
// are present, regardless of whether those bound variables are used. This
// is important for anonymization of binders in `TyCtxt::erase_regions`. We
// specifically detect this case in `visit_binder`.
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for HasTypeFlagsVisitor {
type BreakTy = FoundFlags;
fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
&mut self,
t: &Binder<'tcx, T>,
) -> ControlFlow<Self::BreakTy> {
// If we're looking for any of the HAS_*_LATE_BOUND flags, we need to
// additionally consider the bound vars on the binder itself, even if
// the contents of a the binder (e.g. a `TraitRef`) doesn't reference
// the bound vars.
if self.flags.intersects(TypeFlags::HAS_LATE_BOUND) {
let bound_var_flags = FlagComputation::bound_var_flags(t.bound_vars());
if bound_var_flags.flags.intersects(self.flags) {
return ControlFlow::Break(FoundFlags);
}
}
t.super_visit_with(self)
}
#[inline]
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
// Note: no `super_visit_with` call.
let flags = t.flags();
if flags.intersects(self.flags) {
ControlFlow::Break(FoundFlags)
} else {
ControlFlow::Continue(())
}
}
#[inline]
fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
// Note: no `super_visit_with` call, as usual for `Region`.
let flags = r.type_flags();
if flags.intersects(self.flags) {
ControlFlow::Break(FoundFlags)
} else {
ControlFlow::Continue(())
}
}
#[inline]
fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
// Note: no `super_visit_with` call.
let flags = FlagComputation::for_const(c);
trace!(r.flags=?flags);
if flags.intersects(self.flags) {
ControlFlow::Break(FoundFlags)
} else {
ControlFlow::Continue(())
}
}
#[inline]
fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> {
// Note: no `super_visit_with` call.
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<TyCtxt<'tcx>> for LateBoundRegionsCollector {
fn visit_binder<T: TypeVisitable<TyCtxt<'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::Alias(..) = 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<TyCtxt<'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(())
}
}