| //! 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::subst::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 = self.infcx.tcx.mk_ty_var(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::GeneratorWitnessMIR(..) |
| | 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 = self.infcx.tcx.mk_const(ty::InferConst::Var(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::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_FREE_REGIONS | // `HAS_RE_PLACEHOLDER` implies `HAS_FREE_REGIONS` |
| TypeFlags::HAS_TY_PLACEHOLDER | |
| TypeFlags::HAS_CT_PLACEHOLDER |
| } else { |
| TypeFlags::HAS_INFER |
| | TypeFlags::HAS_RE_PLACEHOLDER |
| | TypeFlags::HAS_TY_PLACEHOLDER |
| | TypeFlags::HAS_CT_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) => { |
| 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(None) }; |
| self.interner().mk_re_late_bound(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()); |
| self.interner().mk_bound(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()); |
| self.interner().mk_const( |
| ty::ConstKind::Bound(self.binder_index, var), |
| self.fold_ty(const_var.ty()), |
| ) |
| } |
| } |
| } |
