| use std::cmp::Ordering; |
| |
| use crate::infer::InferCtxt; |
| use rustc_middle::infer::canonical::Canonical; |
| use rustc_middle::infer::canonical::CanonicalTyVarKind; |
| use rustc_middle::infer::canonical::CanonicalVarInfo; |
| use rustc_middle::infer::canonical::CanonicalVarInfos; |
| use rustc_middle::infer::canonical::CanonicalVarKind; |
| use rustc_middle::ty::BoundRegionKind::BrAnon; |
| use rustc_middle::ty::BoundTyKind; |
| use rustc_middle::ty::TyCtxt; |
| use rustc_middle::ty::TypeVisitableExt; |
| use rustc_middle::ty::{self, Ty}; |
| use rustc_middle::ty::{TypeFoldable, TypeFolder, TypeSuperFoldable}; |
| |
| /// Whether we're canonicalizing a query input or the query response. |
| /// |
| /// When canonicalizing an input we're in the context of the caller |
| /// while canonicalizing the response happens in the context of the |
| /// query. |
| #[derive(Debug, Clone, Copy)] |
| pub enum CanonicalizeMode { |
| Input, |
| /// FIXME: We currently return region constraints referring to |
| /// placeholders and inference variables from a binder instantiated |
| /// inside of the query. |
| /// |
| /// In the long term we should eagerly deal with these constraints |
| /// inside of the query and only propagate constraints which are |
| /// actually nameable by the caller. |
| Response { |
| /// The highest universe nameable by the caller. |
| /// |
| /// All variables in a universe nameable by the caller get mapped |
| /// to the root universe in the response and then mapped back to |
| /// their correct universe when applying the query response in the |
| /// context of the caller. |
| /// |
| /// This doesn't work for universes created inside of the query so |
| /// we do remember their universe in the response. |
| max_input_universe: ty::UniverseIndex, |
| }, |
| } |
| |
| pub struct Canonicalizer<'a, 'tcx> { |
| infcx: &'a InferCtxt<'tcx>, |
| canonicalize_mode: CanonicalizeMode, |
| |
| variables: &'a mut Vec<ty::GenericArg<'tcx>>, |
| primitive_var_infos: Vec<CanonicalVarInfo<'tcx>>, |
| binder_index: ty::DebruijnIndex, |
| } |
| |
| impl<'a, 'tcx> Canonicalizer<'a, 'tcx> { |
| #[instrument(level = "debug", skip(infcx), ret)] |
| pub fn canonicalize<T: TypeFoldable<TyCtxt<'tcx>>>( |
| infcx: &'a InferCtxt<'tcx>, |
| canonicalize_mode: CanonicalizeMode, |
| variables: &'a mut Vec<ty::GenericArg<'tcx>>, |
| value: T, |
| ) -> Canonical<'tcx, T> { |
| let mut canonicalizer = Canonicalizer { |
| infcx, |
| canonicalize_mode, |
| |
| variables, |
| primitive_var_infos: Vec::new(), |
| binder_index: ty::INNERMOST, |
| }; |
| |
| let value = value.fold_with(&mut canonicalizer); |
| assert!(!value.has_infer()); |
| assert!(!value.has_placeholders()); |
| |
| let (max_universe, variables) = canonicalizer.finalize(); |
| |
| Canonical { max_universe, variables, value } |
| } |
| |
| fn finalize(self) -> (ty::UniverseIndex, CanonicalVarInfos<'tcx>) { |
| let mut var_infos = self.primitive_var_infos; |
| // See the rustc-dev-guide section about how we deal with universes |
| // during canonicalization in the new solver. |
| match self.canonicalize_mode { |
| // We try to deduplicate as many query calls as possible and hide |
| // all information which should not matter for the solver. |
| // |
| // For this we compress universes as much as possible. |
| CanonicalizeMode::Input => {} |
| // When canonicalizing a response we map a universes already entered |
| // by the caller to the root universe and only return useful universe |
| // information for placeholders and inference variables created inside |
| // of the query. |
| CanonicalizeMode::Response { max_input_universe } => { |
| for var in var_infos.iter_mut() { |
| let uv = var.universe(); |
| let new_uv = ty::UniverseIndex::from( |
| uv.index().saturating_sub(max_input_universe.index()), |
| ); |
| *var = var.with_updated_universe(new_uv); |
| } |
| let max_universe = var_infos |
| .iter() |
| .map(|info| info.universe()) |
| .max() |
| .unwrap_or(ty::UniverseIndex::ROOT); |
| |
| let var_infos = self.infcx.tcx.mk_canonical_var_infos(&var_infos); |
| return (max_universe, var_infos); |
| } |
| } |
| |
| // Given a `var_infos` with existentials `En` and universals `Un` in |
| // universes `n`, this algorithm compresses them in place so that: |
| // |
| // - the new universe indices are as small as possible |
| // - we only create a new universe if we would otherwise put a placeholder in |
| // the same compressed universe as an existential which cannot name it |
| // |
| // Let's walk through an example: |
| // - var_infos: [E0, U1, E5, U2, E2, E6, U6], curr_compressed_uv: 0, next_orig_uv: 0 |
| // - var_infos: [E0, U1, E5, U2, E2, E6, U6], curr_compressed_uv: 0, next_orig_uv: 1 |
| // - var_infos: [E0, U1, E5, U2, E2, E6, U6], curr_compressed_uv: 1, next_orig_uv: 2 |
| // - var_infos: [E0, U1, E5, U1, E1, E6, U6], curr_compressed_uv: 1, next_orig_uv: 5 |
| // - var_infos: [E0, U1, E1, U1, E1, E6, U6], curr_compressed_uv: 1, next_orig_uv: 6 |
| // - var_infos: [E0, U1, E1, U1, E1, E2, U2], curr_compressed_uv: 2, next_orig_uv: - |
| // |
| // This algorithm runs in `O(n²)` where `n` is the number of different universe |
| // indices in the input. This should be fine as `n` is expected to be small. |
| let mut curr_compressed_uv = ty::UniverseIndex::ROOT; |
| let mut existential_in_new_uv = false; |
| let mut next_orig_uv = Some(ty::UniverseIndex::ROOT); |
| while let Some(orig_uv) = next_orig_uv.take() { |
| let mut update_uv = |var: &mut CanonicalVarInfo<'tcx>, orig_uv, is_existential| { |
| let uv = var.universe(); |
| match uv.cmp(&orig_uv) { |
| Ordering::Less => (), // Already updated |
| Ordering::Equal => { |
| if is_existential { |
| existential_in_new_uv = true; |
| } else if existential_in_new_uv { |
| // `var` is a placeholder from a universe which is not nameable |
| // by an existential which we already put into the compressed |
| // universe `curr_compressed_uv`. We therefore have to create a |
| // new universe for `var`. |
| curr_compressed_uv = curr_compressed_uv.next_universe(); |
| existential_in_new_uv = false; |
| } |
| |
| *var = var.with_updated_universe(curr_compressed_uv); |
| } |
| Ordering::Greater => { |
| // We can ignore this variable in this iteration. We only look at |
| // universes which actually occur in the input for performance. |
| // |
| // For this we set `next_orig_uv` to the next smallest, not yet compressed, |
| // universe of the input. |
| if next_orig_uv.map_or(true, |curr_next_uv| uv.cannot_name(curr_next_uv)) { |
| next_orig_uv = Some(uv); |
| } |
| } |
| } |
| }; |
| |
| // For each universe which occurs in the input, we first iterate over all |
| // placeholders and then over all inference variables. |
| // |
| // Whenever we compress the universe of a placeholder, no existential with |
| // an already compressed universe can name that placeholder. |
| for is_existential in [false, true] { |
| for var in var_infos.iter_mut() { |
| // We simply put all regions from the input into the highest |
| // compressed universe, so we only deal with them at the end. |
| if !var.is_region() { |
| if is_existential == var.is_existential() { |
| update_uv(var, orig_uv, is_existential) |
| } |
| } |
| } |
| } |
| } |
| |
| for var in var_infos.iter_mut() { |
| if var.is_region() { |
| assert!(var.is_existential()); |
| *var = var.with_updated_universe(curr_compressed_uv); |
| } |
| } |
| |
| let var_infos = self.infcx.tcx.mk_canonical_var_infos(&var_infos); |
| (curr_compressed_uv, var_infos) |
| } |
| } |
| |
| impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> { |
| fn interner(&self) -> TyCtxt<'tcx> { |
| self.infcx.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> { |
| if let ty::ReVar(vid) = *r { |
| let resolved_region = self |
| .infcx |
| .inner |
| .borrow_mut() |
| .unwrap_region_constraints() |
| .opportunistic_resolve_var(self.infcx.tcx, vid); |
| assert_eq!( |
| r, resolved_region, |
| "region var should have been resolved, {r} -> {resolved_region}" |
| ); |
| } |
| |
| let kind = match *r { |
| ty::ReLateBound(..) => return r, |
| |
| ty::ReStatic => match self.canonicalize_mode { |
| CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), |
| CanonicalizeMode::Response { .. } => return r, |
| }, |
| |
| ty::ReErased | ty::ReFree(_) | ty::ReEarlyBound(_) => match self.canonicalize_mode { |
| CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), |
| CanonicalizeMode::Response { .. } => bug!("unexpected region in response: {r:?}"), |
| }, |
| |
| ty::RePlaceholder(placeholder) => match self.canonicalize_mode { |
| // We canonicalize placeholder regions as existentials in query inputs. |
| CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), |
| CanonicalizeMode::Response { max_input_universe } => { |
| // If we have a placeholder region inside of a query, it must be from |
| // a new universe. |
| if max_input_universe.can_name(placeholder.universe) { |
| bug!("new placeholder in universe {max_input_universe:?}: {r:?}"); |
| } |
| CanonicalVarKind::PlaceholderRegion(placeholder) |
| } |
| }, |
| |
| ty::ReVar(_) => match self.canonicalize_mode { |
| CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), |
| CanonicalizeMode::Response { .. } => { |
| CanonicalVarKind::Region(self.infcx.universe_of_region(r)) |
| } |
| }, |
| |
| ty::ReError(_) => return r, |
| }; |
| |
| let existing_bound_var = match self.canonicalize_mode { |
| CanonicalizeMode::Input => None, |
| CanonicalizeMode::Response { .. } => { |
| self.variables.iter().position(|&v| v == r.into()).map(ty::BoundVar::from) |
| } |
| }; |
| let var = existing_bound_var.unwrap_or_else(|| { |
| let var = ty::BoundVar::from(self.variables.len()); |
| self.variables.push(r.into()); |
| self.primitive_var_infos.push(CanonicalVarInfo { kind }); |
| var |
| }); |
| let br = ty::BoundRegion { var, kind: BrAnon(None) }; |
| ty::Region::new_late_bound(self.interner(), self.binder_index, br) |
| } |
| |
| fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { |
| let kind = match *t.kind() { |
| ty::Infer(ty::TyVar(vid)) => { |
| assert_eq!(self.infcx.root_var(vid), vid, "ty vid should have been resolved"); |
| let Err(ui) = self.infcx.probe_ty_var(vid) else { |
| bug!("ty var should have been resolved: {t}"); |
| }; |
| CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui)) |
| } |
| ty::Infer(ty::IntVar(vid)) => { |
| assert_eq!(self.infcx.opportunistic_resolve_int_var(vid), t); |
| CanonicalVarKind::Ty(CanonicalTyVarKind::Int) |
| } |
| ty::Infer(ty::FloatVar(vid)) => { |
| assert_eq!(self.infcx.opportunistic_resolve_float_var(vid), t); |
| CanonicalVarKind::Ty(CanonicalTyVarKind::Float) |
| } |
| ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { |
| bug!("fresh var during canonicalization: {t:?}") |
| } |
| ty::Placeholder(placeholder) => match self.canonicalize_mode { |
| CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(ty::Placeholder { |
| universe: placeholder.universe, |
| bound: ty::BoundTy { |
| var: ty::BoundVar::from_usize(self.variables.len()), |
| kind: ty::BoundTyKind::Anon, |
| }, |
| }), |
| CanonicalizeMode::Response { .. } => CanonicalVarKind::PlaceholderTy(placeholder), |
| }, |
| ty::Param(_) => match self.canonicalize_mode { |
| CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(ty::Placeholder { |
| universe: ty::UniverseIndex::ROOT, |
| bound: ty::BoundTy { |
| var: ty::BoundVar::from_usize(self.variables.len()), |
| kind: ty::BoundTyKind::Anon, |
| }, |
| }), |
| CanonicalizeMode::Response { .. } => bug!("param ty in response: {t:?}"), |
| }, |
| ty::Bool |
| | ty::Char |
| | ty::Int(_) |
| | ty::Uint(_) |
| | ty::Float(_) |
| | ty::Adt(_, _) |
| | ty::Foreign(_) |
| | ty::Str |
| | ty::Array(_, _) |
| | ty::Slice(_) |
| | ty::RawPtr(_) |
| | ty::Ref(_, _, _) |
| | ty::FnDef(_, _) |
| | ty::FnPtr(_) |
| | ty::Dynamic(_, _, _) |
| | ty::Closure(_, _) |
| | ty::Generator(_, _, _) |
| | ty::GeneratorWitness(_) |
| | ty::GeneratorWitnessMIR(..) |
| | ty::Never |
| | ty::Tuple(_) |
| | ty::Alias(_, _) |
| | ty::Bound(_, _) |
| | ty::Error(_) => return t.super_fold_with(self), |
| }; |
| |
| let var = ty::BoundVar::from( |
| self.variables.iter().position(|&v| v == t.into()).unwrap_or_else(|| { |
| let var = self.variables.len(); |
| self.variables.push(t.into()); |
| self.primitive_var_infos.push(CanonicalVarInfo { kind }); |
| var |
| }), |
| ); |
| let bt = ty::BoundTy { var, kind: BoundTyKind::Anon }; |
| Ty::new_bound(self.infcx.tcx, self.binder_index, bt) |
| } |
| |
| fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> { |
| let kind = match c.kind() { |
| ty::ConstKind::Infer(ty::InferConst::Var(vid)) => { |
| assert_eq!( |
| self.infcx.root_const_var(vid), |
| vid, |
| "const var should have been resolved" |
| ); |
| let Err(ui) = self.infcx.probe_const_var(vid) else { |
| bug!("const var should have been resolved"); |
| }; |
| // FIXME: we should fold this ty eventually |
| CanonicalVarKind::Const(ui, c.ty()) |
| } |
| ty::ConstKind::Infer(ty::InferConst::Fresh(_)) => { |
| bug!("fresh var during canonicalization: {c:?}") |
| } |
| ty::ConstKind::Placeholder(placeholder) => match self.canonicalize_mode { |
| CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst( |
| ty::Placeholder { |
| universe: placeholder.universe, |
| bound: ty::BoundVar::from(self.variables.len()), |
| }, |
| c.ty(), |
| ), |
| CanonicalizeMode::Response { .. } => { |
| CanonicalVarKind::PlaceholderConst(placeholder, c.ty()) |
| } |
| }, |
| ty::ConstKind::Param(_) => match self.canonicalize_mode { |
| CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst( |
| ty::Placeholder { |
| universe: ty::UniverseIndex::ROOT, |
| bound: ty::BoundVar::from(self.variables.len()), |
| }, |
| c.ty(), |
| ), |
| CanonicalizeMode::Response { .. } => bug!("param ty in response: {c:?}"), |
| }, |
| ty::ConstKind::Bound(_, _) |
| | ty::ConstKind::Unevaluated(_) |
| | ty::ConstKind::Value(_) |
| | ty::ConstKind::Error(_) |
| | ty::ConstKind::Expr(_) => return c.super_fold_with(self), |
| }; |
| |
| let var = ty::BoundVar::from( |
| self.variables.iter().position(|&v| v == c.into()).unwrap_or_else(|| { |
| let var = self.variables.len(); |
| self.variables.push(c.into()); |
| self.primitive_var_infos.push(CanonicalVarInfo { kind }); |
| var |
| }), |
| ); |
| ty::Const::new_bound(self.infcx.tcx, self.binder_index, var, c.ty()) |
| } |
| } |
