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//! This module contains the "canonicalizer" itself.
//!
//! For an overview of what canonicalization is and how it fits into
//! rustc, check out the [chapter in the rustc dev guide][c].
//!
//! [c]: https://rust-lang.github.io/chalk/book/canonical_queries/canonicalization.html
use crate::infer::canonical::{
Canonical, CanonicalTyVarKind, CanonicalVarInfo, CanonicalVarKind, OriginalQueryValues,
};
use crate::infer::InferCtxt;
use rustc_middle::ty::flags::FlagComputation;
use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
use rustc_middle::ty::GenericArg;
use rustc_middle::ty::{self, BoundVar, InferConst, List, Ty, TyCtxt, TypeFlags, TypeVisitableExt};
use std::sync::atomic::Ordering;
use rustc_data_structures::fx::FxHashMap;
use rustc_index::Idx;
use smallvec::SmallVec;
impl<'tcx> InferCtxt<'tcx> {
/// Canonicalizes a query value `V`. When we canonicalize a query,
/// we not only canonicalize unbound inference variables, but we
/// *also* replace all free regions whatsoever. So for example a
/// query like `T: Trait<'static>` would be canonicalized to
///
/// ```text
/// T: Trait<'?0>
/// ```
///
/// with a mapping M that maps `'?0` to `'static`.
///
/// To get a good understanding of what is happening here, check
/// out the [chapter in the rustc dev guide][c].
///
/// [c]: https://rust-lang.github.io/chalk/book/canonical_queries/canonicalization.html#canonicalizing-the-query
pub fn canonicalize_query<V>(
&self,
value: V,
query_state: &mut OriginalQueryValues<'tcx>,
) -> Canonical<'tcx, V>
where
V: TypeFoldable<TyCtxt<'tcx>>,
{
self.tcx.sess.perf_stats.queries_canonicalized.fetch_add(1, Ordering::Relaxed);
Canonicalizer::canonicalize(value, self, self.tcx, &CanonicalizeAllFreeRegions, query_state)
}
/// Like [Self::canonicalize_query], but preserves distinct universes. For
/// example, canonicalizing `&'?0: Trait<'?1>`, where `'?0` is in `U1` and
/// `'?1` is in `U3` would be canonicalized to have `?0` in `U1` and `'?1`
/// in `U2`.
///
/// This is used for Chalk integration.
pub fn canonicalize_query_preserving_universes<V>(
&self,
value: V,
query_state: &mut OriginalQueryValues<'tcx>,
) -> Canonical<'tcx, V>
where
V: TypeFoldable<TyCtxt<'tcx>>,
{
self.tcx.sess.perf_stats.queries_canonicalized.fetch_add(1, Ordering::Relaxed);
Canonicalizer::canonicalize(
value,
self,
self.tcx,
&CanonicalizeAllFreeRegionsPreservingUniverses,
query_state,
)
}
/// Canonicalizes a query *response* `V`. When we canonicalize a
/// query response, we only canonicalize unbound inference
/// variables, and we leave other free regions alone. So,
/// continuing with the example from `canonicalize_query`, if
/// there was an input query `T: Trait<'static>`, it would have
/// been canonicalized to
///
/// ```text
/// T: Trait<'?0>
/// ```
///
/// with a mapping M that maps `'?0` to `'static`. But if we found that there
/// exists only one possible impl of `Trait`, and it looks like
/// ```ignore (illustrative)
/// impl<T> Trait<'static> for T { .. }
/// ```
/// then we would prepare a query result R that (among other
/// things) includes a mapping to `'?0 := 'static`. When
/// canonicalizing this query result R, we would leave this
/// reference to `'static` alone.
///
/// To get a good understanding of what is happening here, check
/// out the [chapter in the rustc dev guide][c].
///
/// [c]: https://rust-lang.github.io/chalk/book/canonical_queries/canonicalization.html#canonicalizing-the-query-result
pub fn canonicalize_response<V>(&self, value: V) -> Canonical<'tcx, V>
where
V: TypeFoldable<TyCtxt<'tcx>>,
{
let mut query_state = OriginalQueryValues::default();
Canonicalizer::canonicalize(
value,
self,
self.tcx,
&CanonicalizeQueryResponse,
&mut query_state,
)
}
pub fn canonicalize_user_type_annotation<V>(&self, value: V) -> Canonical<'tcx, V>
where
V: TypeFoldable<TyCtxt<'tcx>>,
{
let mut query_state = OriginalQueryValues::default();
Canonicalizer::canonicalize(
value,
self,
self.tcx,
&CanonicalizeUserTypeAnnotation,
&mut query_state,
)
}
/// A variant of `canonicalize_query` that does not
/// canonicalize `'static`. This is useful when
/// the query implementation can perform more efficient
/// handling of `'static` regions (e.g. trait evaluation).
pub fn canonicalize_query_keep_static<V>(
&self,
value: V,
query_state: &mut OriginalQueryValues<'tcx>,
) -> Canonical<'tcx, V>
where
V: TypeFoldable<TyCtxt<'tcx>>,
{
self.tcx.sess.perf_stats.queries_canonicalized.fetch_add(1, Ordering::Relaxed);
Canonicalizer::canonicalize(
value,
self,
self.tcx,
&CanonicalizeFreeRegionsOtherThanStatic,
query_state,
)
}
}
/// Controls how we canonicalize "free regions" that are not inference
/// variables. This depends on what we are canonicalizing *for* --
/// e.g., if we are canonicalizing to create a query, we want to
/// replace those with inference variables, since we want to make a
/// maximally general query. But if we are canonicalizing a *query
/// response*, then we don't typically replace free regions, as they
/// must have been introduced from other parts of the system.
trait CanonicalizeMode {
fn canonicalize_free_region<'tcx>(
&self,
canonicalizer: &mut Canonicalizer<'_, 'tcx>,
r: ty::Region<'tcx>,
) -> ty::Region<'tcx>;
fn any(&self) -> bool;
// Do we preserve universe of variables.
fn preserve_universes(&self) -> bool;
}
struct CanonicalizeQueryResponse;
impl CanonicalizeMode for CanonicalizeQueryResponse {
fn canonicalize_free_region<'tcx>(
&self,
canonicalizer: &mut Canonicalizer<'_, 'tcx>,
r: ty::Region<'tcx>,
) -> ty::Region<'tcx> {
match *r {
ty::ReFree(_) | ty::ReErased | ty::ReStatic | ty::ReEarlyBound(..) => r,
ty::RePlaceholder(placeholder) => canonicalizer.canonical_var_for_region(
CanonicalVarInfo { kind: CanonicalVarKind::PlaceholderRegion(placeholder) },
r,
),
ty::ReVar(vid) => {
let universe = canonicalizer.region_var_universe(vid);
canonicalizer.canonical_var_for_region(
CanonicalVarInfo { kind: CanonicalVarKind::Region(universe) },
r,
)
}
_ => {
// Other than `'static` or `'empty`, the query
// response should be executing in a fully
// canonicalized environment, so there shouldn't be
// any other region names it can come up.
//
// rust-lang/rust#57464: `impl Trait` can leak local
// scopes (in manner violating typeck). Therefore, use
// `delay_span_bug` to allow type error over an ICE.
canonicalizer.tcx.sess.delay_span_bug(
rustc_span::DUMMY_SP,
format!("unexpected region in query response: `{r:?}`"),
);
r
}
}
}
fn any(&self) -> bool {
false
}
fn preserve_universes(&self) -> bool {
true
}
}
struct CanonicalizeUserTypeAnnotation;
impl CanonicalizeMode for CanonicalizeUserTypeAnnotation {
fn canonicalize_free_region<'tcx>(
&self,
canonicalizer: &mut Canonicalizer<'_, 'tcx>,
r: ty::Region<'tcx>,
) -> ty::Region<'tcx> {
match *r {
ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReErased | ty::ReStatic | ty::ReError(_) => r,
ty::ReVar(_) => canonicalizer.canonical_var_for_region_in_root_universe(r),
ty::RePlaceholder(..) | ty::ReLateBound(..) => {
// We only expect region names that the user can type.
bug!("unexpected region in query response: `{:?}`", r)
}
}
}
fn any(&self) -> bool {
false
}
fn preserve_universes(&self) -> bool {
false
}
}
struct CanonicalizeAllFreeRegions;
impl CanonicalizeMode for CanonicalizeAllFreeRegions {
fn canonicalize_free_region<'tcx>(
&self,
canonicalizer: &mut Canonicalizer<'_, 'tcx>,
r: ty::Region<'tcx>,
) -> ty::Region<'tcx> {
canonicalizer.canonical_var_for_region_in_root_universe(r)
}
fn any(&self) -> bool {
true
}
fn preserve_universes(&self) -> bool {
false
}
}
struct CanonicalizeAllFreeRegionsPreservingUniverses;
impl CanonicalizeMode for CanonicalizeAllFreeRegionsPreservingUniverses {
fn canonicalize_free_region<'tcx>(
&self,
canonicalizer: &mut Canonicalizer<'_, 'tcx>,
r: ty::Region<'tcx>,
) -> ty::Region<'tcx> {
let universe = canonicalizer.infcx.universe_of_region(r);
canonicalizer.canonical_var_for_region(
CanonicalVarInfo { kind: CanonicalVarKind::Region(universe) },
r,
)
}
fn any(&self) -> bool {
true
}
fn preserve_universes(&self) -> bool {
true
}
}
struct CanonicalizeFreeRegionsOtherThanStatic;
impl CanonicalizeMode for CanonicalizeFreeRegionsOtherThanStatic {
fn canonicalize_free_region<'tcx>(
&self,
canonicalizer: &mut Canonicalizer<'_, 'tcx>,
r: ty::Region<'tcx>,
) -> ty::Region<'tcx> {
if r.is_static() { r } else { canonicalizer.canonical_var_for_region_in_root_universe(r) }
}
fn any(&self) -> bool {
true
}
fn preserve_universes(&self) -> bool {
false
}
}
struct Canonicalizer<'cx, 'tcx> {
infcx: &'cx InferCtxt<'tcx>,
tcx: TyCtxt<'tcx>,
variables: SmallVec<[CanonicalVarInfo<'tcx>; 8]>,
query_state: &'cx mut OriginalQueryValues<'tcx>,
// Note that indices is only used once `var_values` is big enough to be
// heap-allocated.
indices: FxHashMap<GenericArg<'tcx>, BoundVar>,
canonicalize_mode: &'cx dyn CanonicalizeMode,
needs_canonical_flags: TypeFlags,
binder_index: ty::DebruijnIndex,
}
impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
fn interner(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_binder<T>(&mut self, t: ty::Binder<'tcx, T>) -> ty::Binder<'tcx, T>
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
self.binder_index.shift_in(1);
let t = t.super_fold_with(self);
self.binder_index.shift_out(1);
t
}
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
match *r {
ty::ReLateBound(index, ..) => {
if index >= self.binder_index {
bug!("escaping late-bound region during canonicalization");
} else {
r
}
}
ty::ReVar(vid) => {
let resolved = self
.infcx
.inner
.borrow_mut()
.unwrap_region_constraints()
.opportunistic_resolve_var(self.tcx, vid);
debug!(
"canonical: region var found with vid {vid:?}, \
opportunistically resolved to {resolved:?}",
);
self.canonicalize_mode.canonicalize_free_region(self, resolved)
}
ty::ReStatic
| ty::ReEarlyBound(..)
| ty::ReError(_)
| ty::ReFree(_)
| ty::RePlaceholder(..)
| ty::ReErased => self.canonicalize_mode.canonicalize_free_region(self, r),
}
}
fn fold_ty(&mut self, mut t: Ty<'tcx>) -> Ty<'tcx> {
match *t.kind() {
ty::Infer(ty::TyVar(mut vid)) => {
// We need to canonicalize the *root* of our ty var.
// This is so that our canonical response correctly reflects
// any equated inference vars correctly!
let root_vid = self.infcx.root_var(vid);
if root_vid != vid {
t = Ty::new_var(self.infcx.tcx, root_vid);
vid = root_vid;
}
debug!("canonical: type var found with vid {:?}", vid);
match self.infcx.probe_ty_var(vid) {
// `t` could be a float / int variable; canonicalize that instead.
Ok(t) => {
debug!("(resolved to {:?})", t);
self.fold_ty(t)
}
// `TyVar(vid)` is unresolved, track its universe index in the canonicalized
// result.
Err(mut ui) => {
if !self.canonicalize_mode.preserve_universes() {
// FIXME: perf problem described in #55921.
ui = ty::UniverseIndex::ROOT;
}
self.canonicalize_ty_var(
CanonicalVarInfo {
kind: CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui)),
},
t,
)
}
}
}
ty::Infer(ty::IntVar(vid)) => {
let nt = self.infcx.opportunistic_resolve_int_var(vid);
if nt != t {
return self.fold_ty(nt);
} else {
self.canonicalize_ty_var(
CanonicalVarInfo { kind: CanonicalVarKind::Ty(CanonicalTyVarKind::Int) },
t,
)
}
}
ty::Infer(ty::FloatVar(vid)) => {
let nt = self.infcx.opportunistic_resolve_float_var(vid);
if nt != t {
return self.fold_ty(nt);
} else {
self.canonicalize_ty_var(
CanonicalVarInfo { kind: CanonicalVarKind::Ty(CanonicalTyVarKind::Float) },
t,
)
}
}
ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
bug!("encountered a fresh type during canonicalization")
}
ty::Placeholder(mut placeholder) => {
if !self.canonicalize_mode.preserve_universes() {
placeholder.universe = ty::UniverseIndex::ROOT;
}
self.canonicalize_ty_var(
CanonicalVarInfo { kind: CanonicalVarKind::PlaceholderTy(placeholder) },
t,
)
}
ty::Bound(debruijn, _) => {
if debruijn >= self.binder_index {
bug!("escaping bound type during canonicalization")
} else {
t
}
}
ty::Closure(..)
| ty::Generator(..)
| ty::GeneratorWitness(..)
| ty::Bool
| ty::Char
| ty::Int(..)
| ty::Uint(..)
| ty::Float(..)
| ty::Adt(..)
| ty::Str
| ty::Error(_)
| ty::Array(..)
| ty::Slice(..)
| ty::RawPtr(..)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(_)
| ty::Dynamic(..)
| ty::Never
| ty::Tuple(..)
| ty::Alias(..)
| ty::Foreign(..)
| ty::Param(..) => {
if t.flags().intersects(self.needs_canonical_flags) {
t.super_fold_with(self)
} else {
t
}
}
}
}
fn fold_const(&mut self, mut ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
match ct.kind() {
ty::ConstKind::Infer(InferConst::Var(mut vid)) => {
// We need to canonicalize the *root* of our const var.
// This is so that our canonical response correctly reflects
// any equated inference vars correctly!
let root_vid = self.infcx.root_const_var(vid);
if root_vid != vid {
ct = ty::Const::new_var(self.infcx.tcx, root_vid, ct.ty());
vid = root_vid;
}
debug!("canonical: const var found with vid {:?}", vid);
match self.infcx.probe_const_var(vid) {
Ok(c) => {
debug!("(resolved to {:?})", c);
return self.fold_const(c);
}
// `ConstVar(vid)` is unresolved, track its universe index in the
// canonicalized result
Err(mut ui) => {
if !self.canonicalize_mode.preserve_universes() {
// FIXME: perf problem described in #55921.
ui = ty::UniverseIndex::ROOT;
}
return self.canonicalize_const_var(
CanonicalVarInfo { kind: CanonicalVarKind::Const(ui, ct.ty()) },
ct,
);
}
}
}
ty::ConstKind::Infer(InferConst::EffectVar(vid)) => {
match self.infcx.probe_effect_var(vid) {
Some(value) => return self.fold_const(value.as_const(self.infcx.tcx)),
None => {
return self.canonicalize_const_var(
CanonicalVarInfo { kind: CanonicalVarKind::Effect },
ct,
);
}
}
}
ty::ConstKind::Infer(InferConst::Fresh(_)) => {
bug!("encountered a fresh const during canonicalization")
}
ty::ConstKind::Bound(debruijn, _) => {
if debruijn >= self.binder_index {
bug!("escaping bound const during canonicalization")
} else {
return ct;
}
}
ty::ConstKind::Placeholder(placeholder) => {
return self.canonicalize_const_var(
CanonicalVarInfo {
kind: CanonicalVarKind::PlaceholderConst(placeholder, ct.ty()),
},
ct,
);
}
_ => {}
}
let flags = FlagComputation::for_const(ct);
if flags.intersects(self.needs_canonical_flags) { ct.super_fold_with(self) } else { ct }
}
}
impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
/// The main `canonicalize` method, shared impl of
/// `canonicalize_query` and `canonicalize_response`.
fn canonicalize<V>(
value: V,
infcx: &InferCtxt<'tcx>,
tcx: TyCtxt<'tcx>,
canonicalize_region_mode: &dyn CanonicalizeMode,
query_state: &mut OriginalQueryValues<'tcx>,
) -> Canonical<'tcx, V>
where
V: TypeFoldable<TyCtxt<'tcx>>,
{
let needs_canonical_flags = if canonicalize_region_mode.any() {
TypeFlags::HAS_INFER | TypeFlags::HAS_PLACEHOLDER | TypeFlags::HAS_FREE_REGIONS
} else {
TypeFlags::HAS_INFER | TypeFlags::HAS_PLACEHOLDER
};
// Fast path: nothing that needs to be canonicalized.
if !value.has_type_flags(needs_canonical_flags) {
let canon_value = Canonical {
max_universe: ty::UniverseIndex::ROOT,
variables: List::empty(),
value,
};
return canon_value;
}
let mut canonicalizer = Canonicalizer {
infcx,
tcx,
canonicalize_mode: canonicalize_region_mode,
needs_canonical_flags,
variables: SmallVec::new(),
query_state,
indices: FxHashMap::default(),
binder_index: ty::INNERMOST,
};
let out_value = value.fold_with(&mut canonicalizer);
// Once we have canonicalized `out_value`, it should not
// contain anything that ties it to this inference context
// anymore.
debug_assert!(!out_value.has_infer() && !out_value.has_placeholders());
let canonical_variables =
tcx.mk_canonical_var_infos(&canonicalizer.universe_canonicalized_variables());
let max_universe = canonical_variables
.iter()
.map(|cvar| cvar.universe())
.max()
.unwrap_or(ty::UniverseIndex::ROOT);
Canonical { max_universe, variables: canonical_variables, value: out_value }
}
/// Creates a canonical variable replacing `kind` from the input,
/// or returns an existing variable if `kind` has already been
/// seen. `kind` is expected to be an unbound variable (or
/// potentially a free region).
fn canonical_var(&mut self, info: CanonicalVarInfo<'tcx>, kind: GenericArg<'tcx>) -> BoundVar {
let Canonicalizer { variables, query_state, indices, .. } = self;
let var_values = &mut query_state.var_values;
let universe = info.universe();
if universe != ty::UniverseIndex::ROOT {
assert!(self.canonicalize_mode.preserve_universes());
// Insert universe into the universe map. To preserve the order of the
// universes in the value being canonicalized, we don't update the
// universe in `info` until we have finished canonicalizing.
match query_state.universe_map.binary_search(&universe) {
Err(idx) => query_state.universe_map.insert(idx, universe),
Ok(_) => {}
}
}
// This code is hot. `variables` and `var_values` are usually small
// (fewer than 8 elements ~95% of the time). They are SmallVec's to
// avoid allocations in those cases. We also don't use `indices` to
// determine if a kind has been seen before until the limit of 8 has
// been exceeded, to also avoid allocations for `indices`.
if !var_values.spilled() {
// `var_values` is stack-allocated. `indices` isn't used yet. Do a
// direct linear search of `var_values`.
if let Some(idx) = var_values.iter().position(|&k| k == kind) {
// `kind` is already present in `var_values`.
BoundVar::new(idx)
} else {
// `kind` isn't present in `var_values`. Append it. Likewise
// for `info` and `variables`.
variables.push(info);
var_values.push(kind);
assert_eq!(variables.len(), var_values.len());
// If `var_values` has become big enough to be heap-allocated,
// fill up `indices` to facilitate subsequent lookups.
if var_values.spilled() {
assert!(indices.is_empty());
*indices = var_values
.iter()
.enumerate()
.map(|(i, &kind)| (kind, BoundVar::new(i)))
.collect();
}
// The cv is the index of the appended element.
BoundVar::new(var_values.len() - 1)
}
} else {
// `var_values` is large. Do a hashmap search via `indices`.
*indices.entry(kind).or_insert_with(|| {
variables.push(info);
var_values.push(kind);
assert_eq!(variables.len(), var_values.len());
BoundVar::new(variables.len() - 1)
})
}
}
/// Replaces the universe indexes used in `var_values` with their index in
/// `query_state.universe_map`. This minimizes the maximum universe used in
/// the canonicalized value.
fn universe_canonicalized_variables(self) -> SmallVec<[CanonicalVarInfo<'tcx>; 8]> {
if self.query_state.universe_map.len() == 1 {
return self.variables;
}
let reverse_universe_map: FxHashMap<ty::UniverseIndex, ty::UniverseIndex> = self
.query_state
.universe_map
.iter()
.enumerate()
.map(|(idx, universe)| (*universe, ty::UniverseIndex::from_usize(idx)))
.collect();
self.variables
.iter()
.map(|v| CanonicalVarInfo {
kind: match v.kind {
CanonicalVarKind::Ty(CanonicalTyVarKind::Int | CanonicalTyVarKind::Float)
| CanonicalVarKind::Effect => {
return *v;
}
CanonicalVarKind::Ty(CanonicalTyVarKind::General(u)) => {
CanonicalVarKind::Ty(CanonicalTyVarKind::General(reverse_universe_map[&u]))
}
CanonicalVarKind::Region(u) => {
CanonicalVarKind::Region(reverse_universe_map[&u])
}
CanonicalVarKind::Const(u, t) => {
CanonicalVarKind::Const(reverse_universe_map[&u], t)
}
CanonicalVarKind::PlaceholderTy(placeholder) => {
CanonicalVarKind::PlaceholderTy(ty::Placeholder {
universe: reverse_universe_map[&placeholder.universe],
..placeholder
})
}
CanonicalVarKind::PlaceholderRegion(placeholder) => {
CanonicalVarKind::PlaceholderRegion(ty::Placeholder {
universe: reverse_universe_map[&placeholder.universe],
..placeholder
})
}
CanonicalVarKind::PlaceholderConst(placeholder, t) => {
CanonicalVarKind::PlaceholderConst(
ty::Placeholder {
universe: reverse_universe_map[&placeholder.universe],
..placeholder
},
t,
)
}
},
})
.collect()
}
/// Shorthand helper that creates a canonical region variable for
/// `r` (always in the root universe). The reason that we always
/// put these variables into the root universe is because this
/// method is used during **query construction:** in that case, we
/// are taking all the regions and just putting them into the most
/// generic context we can. This may generate solutions that don't
/// fit (e.g., that equate some region variable with a placeholder
/// it can't name) on the caller side, but that's ok, the caller
/// can figure that out. In the meantime, it maximizes our
/// caching.
///
/// (This works because unification never fails -- and hence trait
/// selection is never affected -- due to a universe mismatch.)
fn canonical_var_for_region_in_root_universe(
&mut self,
r: ty::Region<'tcx>,
) -> ty::Region<'tcx> {
self.canonical_var_for_region(
CanonicalVarInfo { kind: CanonicalVarKind::Region(ty::UniverseIndex::ROOT) },
r,
)
}
/// Returns the universe in which `vid` is defined.
fn region_var_universe(&self, vid: ty::RegionVid) -> ty::UniverseIndex {
self.infcx.inner.borrow_mut().unwrap_region_constraints().var_universe(vid)
}
/// Creates a canonical variable (with the given `info`)
/// representing the region `r`; return a region referencing it.
fn canonical_var_for_region(
&mut self,
info: CanonicalVarInfo<'tcx>,
r: ty::Region<'tcx>,
) -> ty::Region<'tcx> {
let var = self.canonical_var(info, r.into());
let br = ty::BoundRegion { var, kind: ty::BrAnon };
ty::Region::new_late_bound(self.interner(), self.binder_index, br)
}
/// Given a type variable `ty_var` of the given kind, first check
/// if `ty_var` is bound to anything; if so, canonicalize
/// *that*. Otherwise, create a new canonical variable for
/// `ty_var`.
fn canonicalize_ty_var(&mut self, info: CanonicalVarInfo<'tcx>, ty_var: Ty<'tcx>) -> Ty<'tcx> {
let infcx = self.infcx;
let bound_to = infcx.shallow_resolve(ty_var);
if bound_to != ty_var {
self.fold_ty(bound_to)
} else {
let var = self.canonical_var(info, ty_var.into());
Ty::new_bound(self.tcx, self.binder_index, var.into())
}
}
/// Given a type variable `const_var` of the given kind, first check
/// if `const_var` is bound to anything; if so, canonicalize
/// *that*. Otherwise, create a new canonical variable for
/// `const_var`.
fn canonicalize_const_var(
&mut self,
info: CanonicalVarInfo<'tcx>,
const_var: ty::Const<'tcx>,
) -> ty::Const<'tcx> {
let infcx = self.infcx;
let bound_to = infcx.shallow_resolve(const_var);
if bound_to != const_var {
self.fold_const(bound_to)
} else {
let var = self.canonical_var(info, const_var.into());
ty::Const::new_bound(self.tcx, self.binder_index, var, self.fold_ty(const_var.ty()))
}
}
}