| //! Unification and canonicalization logic. |
| |
| use std::{fmt, iter, mem}; |
| |
| use chalk_ir::{ |
| cast::Cast, fold::TypeFoldable, interner::HasInterner, zip::Zip, CanonicalVarKind, FloatTy, |
| IntTy, TyVariableKind, UniverseIndex, |
| }; |
| use chalk_solve::infer::ParameterEnaVariableExt; |
| use either::Either; |
| use ena::unify::UnifyKey; |
| use hir_expand::name; |
| use triomphe::Arc; |
| |
| use super::{InferOk, InferResult, InferenceContext, TypeError}; |
| use crate::{ |
| consteval::unknown_const, db::HirDatabase, fold_tys_and_consts, static_lifetime, |
| to_chalk_trait_id, traits::FnTrait, AliasEq, AliasTy, BoundVar, Canonical, Const, ConstValue, |
| DebruijnIndex, GenericArg, GenericArgData, Goal, Guidance, InEnvironment, InferenceVar, |
| Interner, Lifetime, ParamKind, ProjectionTy, ProjectionTyExt, Scalar, Solution, Substitution, |
| TraitEnvironment, Ty, TyBuilder, TyExt, TyKind, VariableKind, |
| }; |
| |
| impl InferenceContext<'_> { |
| pub(super) fn canonicalize<T: TypeFoldable<Interner> + HasInterner<Interner = Interner>>( |
| &mut self, |
| t: T, |
| ) -> Canonicalized<T> |
| where |
| T: HasInterner<Interner = Interner>, |
| { |
| self.table.canonicalize(t) |
| } |
| } |
| |
| #[derive(Debug, Clone)] |
| pub(crate) struct Canonicalized<T> |
| where |
| T: HasInterner<Interner = Interner>, |
| { |
| pub(crate) value: Canonical<T>, |
| free_vars: Vec<GenericArg>, |
| } |
| |
| impl<T: HasInterner<Interner = Interner>> Canonicalized<T> { |
| pub(crate) fn apply_solution( |
| &self, |
| ctx: &mut InferenceTable<'_>, |
| solution: Canonical<Substitution>, |
| ) { |
| // the solution may contain new variables, which we need to convert to new inference vars |
| let new_vars = Substitution::from_iter( |
| Interner, |
| solution.binders.iter(Interner).map(|k| match &k.kind { |
| VariableKind::Ty(TyVariableKind::General) => ctx.new_type_var().cast(Interner), |
| VariableKind::Ty(TyVariableKind::Integer) => ctx.new_integer_var().cast(Interner), |
| VariableKind::Ty(TyVariableKind::Float) => ctx.new_float_var().cast(Interner), |
| // Chalk can sometimes return new lifetime variables. We just use the static lifetime everywhere |
| VariableKind::Lifetime => static_lifetime().cast(Interner), |
| VariableKind::Const(ty) => ctx.new_const_var(ty.clone()).cast(Interner), |
| }), |
| ); |
| for (i, v) in solution.value.iter(Interner).enumerate() { |
| let var = self.free_vars[i].clone(); |
| if let Some(ty) = v.ty(Interner) { |
| // eagerly replace projections in the type; we may be getting types |
| // e.g. from where clauses where this hasn't happened yet |
| let ty = ctx.normalize_associated_types_in(new_vars.apply(ty.clone(), Interner)); |
| ctx.unify(var.assert_ty_ref(Interner), &ty); |
| } else { |
| let _ = ctx.try_unify(&var, &new_vars.apply(v.clone(), Interner)); |
| } |
| } |
| } |
| } |
| |
| pub fn could_unify( |
| db: &dyn HirDatabase, |
| env: Arc<TraitEnvironment>, |
| tys: &Canonical<(Ty, Ty)>, |
| ) -> bool { |
| unify(db, env, tys).is_some() |
| } |
| |
| pub(crate) fn unify( |
| db: &dyn HirDatabase, |
| env: Arc<TraitEnvironment>, |
| tys: &Canonical<(Ty, Ty)>, |
| ) -> Option<Substitution> { |
| let mut table = InferenceTable::new(db, env); |
| let vars = Substitution::from_iter( |
| Interner, |
| tys.binders.iter(Interner).map(|it| match &it.kind { |
| chalk_ir::VariableKind::Ty(_) => table.new_type_var().cast(Interner), |
| // FIXME: maybe wrong? |
| chalk_ir::VariableKind::Lifetime => table.new_type_var().cast(Interner), |
| chalk_ir::VariableKind::Const(ty) => table.new_const_var(ty.clone()).cast(Interner), |
| }), |
| ); |
| let ty1_with_vars = vars.apply(tys.value.0.clone(), Interner); |
| let ty2_with_vars = vars.apply(tys.value.1.clone(), Interner); |
| if !table.unify(&ty1_with_vars, &ty2_with_vars) { |
| return None; |
| } |
| // default any type vars that weren't unified back to their original bound vars |
| // (kind of hacky) |
| let find_var = |iv| { |
| vars.iter(Interner).position(|v| match v.data(Interner) { |
| GenericArgData::Ty(ty) => ty.inference_var(Interner), |
| GenericArgData::Lifetime(lt) => lt.inference_var(Interner), |
| GenericArgData::Const(c) => c.inference_var(Interner), |
| } == Some(iv)) |
| }; |
| let fallback = |iv, kind, default, binder| match kind { |
| chalk_ir::VariableKind::Ty(_ty_kind) => find_var(iv) |
| .map_or(default, |i| BoundVar::new(binder, i).to_ty(Interner).cast(Interner)), |
| chalk_ir::VariableKind::Lifetime => find_var(iv) |
| .map_or(default, |i| BoundVar::new(binder, i).to_lifetime(Interner).cast(Interner)), |
| chalk_ir::VariableKind::Const(ty) => find_var(iv) |
| .map_or(default, |i| BoundVar::new(binder, i).to_const(Interner, ty).cast(Interner)), |
| }; |
| Some(Substitution::from_iter( |
| Interner, |
| vars.iter(Interner).map(|v| table.resolve_with_fallback(v.clone(), &fallback)), |
| )) |
| } |
| |
| bitflags::bitflags! { |
| #[derive(Default, Clone, Copy)] |
| pub(crate) struct TypeVariableFlags: u8 { |
| const DIVERGING = 1 << 0; |
| const INTEGER = 1 << 1; |
| const FLOAT = 1 << 2; |
| } |
| } |
| |
| type ChalkInferenceTable = chalk_solve::infer::InferenceTable<Interner>; |
| |
| #[derive(Clone)] |
| pub(crate) struct InferenceTable<'a> { |
| pub(crate) db: &'a dyn HirDatabase, |
| pub(crate) trait_env: Arc<TraitEnvironment>, |
| var_unification_table: ChalkInferenceTable, |
| type_variable_table: Vec<TypeVariableFlags>, |
| pending_obligations: Vec<Canonicalized<InEnvironment<Goal>>>, |
| /// Double buffer used in [`Self::resolve_obligations_as_possible`] to cut down on |
| /// temporary allocations. |
| resolve_obligations_buffer: Vec<Canonicalized<InEnvironment<Goal>>>, |
| } |
| |
| pub(crate) struct InferenceTableSnapshot { |
| var_table_snapshot: chalk_solve::infer::InferenceSnapshot<Interner>, |
| pending_obligations: Vec<Canonicalized<InEnvironment<Goal>>>, |
| type_variable_table_snapshot: Vec<TypeVariableFlags>, |
| } |
| |
| impl<'a> InferenceTable<'a> { |
| pub(crate) fn new(db: &'a dyn HirDatabase, trait_env: Arc<TraitEnvironment>) -> Self { |
| InferenceTable { |
| db, |
| trait_env, |
| var_unification_table: ChalkInferenceTable::new(), |
| type_variable_table: Vec::new(), |
| pending_obligations: Vec::new(), |
| resolve_obligations_buffer: Vec::new(), |
| } |
| } |
| |
| /// Chalk doesn't know about the `diverging` flag, so when it unifies two |
| /// type variables of which one is diverging, the chosen root might not be |
| /// diverging and we have no way of marking it as such at that time. This |
| /// function goes through all type variables and make sure their root is |
| /// marked as diverging if necessary, so that resolving them gives the right |
| /// result. |
| pub(super) fn propagate_diverging_flag(&mut self) { |
| for i in 0..self.type_variable_table.len() { |
| if !self.type_variable_table[i].contains(TypeVariableFlags::DIVERGING) { |
| continue; |
| } |
| let v = InferenceVar::from(i as u32); |
| let root = self.var_unification_table.inference_var_root(v); |
| if let Some(data) = self.type_variable_table.get_mut(root.index() as usize) { |
| *data |= TypeVariableFlags::DIVERGING; |
| } |
| } |
| } |
| |
| pub(super) fn set_diverging(&mut self, iv: InferenceVar, diverging: bool) { |
| self.type_variable_table[iv.index() as usize].set(TypeVariableFlags::DIVERGING, diverging); |
| } |
| |
| fn fallback_value(&self, iv: InferenceVar, kind: TyVariableKind) -> Ty { |
| match kind { |
| _ if self |
| .type_variable_table |
| .get(iv.index() as usize) |
| .map_or(false, |data| data.contains(TypeVariableFlags::DIVERGING)) => |
| { |
| TyKind::Never |
| } |
| TyVariableKind::General => TyKind::Error, |
| TyVariableKind::Integer => TyKind::Scalar(Scalar::Int(IntTy::I32)), |
| TyVariableKind::Float => TyKind::Scalar(Scalar::Float(FloatTy::F64)), |
| } |
| .intern(Interner) |
| } |
| |
| pub(crate) fn canonicalize<T: TypeFoldable<Interner> + HasInterner<Interner = Interner>>( |
| &mut self, |
| t: T, |
| ) -> Canonicalized<T> |
| where |
| T: HasInterner<Interner = Interner>, |
| { |
| // try to resolve obligations before canonicalizing, since this might |
| // result in new knowledge about variables |
| self.resolve_obligations_as_possible(); |
| let result = self.var_unification_table.canonicalize(Interner, t); |
| let free_vars = result |
| .free_vars |
| .into_iter() |
| .map(|free_var| free_var.to_generic_arg(Interner)) |
| .collect(); |
| Canonicalized { value: result.quantified, free_vars } |
| } |
| |
| /// Recurses through the given type, normalizing associated types mentioned |
| /// in it by replacing them by type variables and registering obligations to |
| /// resolve later. This should be done once for every type we get from some |
| /// type annotation (e.g. from a let type annotation, field type or function |
| /// call). `make_ty` handles this already, but e.g. for field types we need |
| /// to do it as well. |
| pub(crate) fn normalize_associated_types_in<T>(&mut self, ty: T) -> T |
| where |
| T: HasInterner<Interner = Interner> + TypeFoldable<Interner>, |
| { |
| fold_tys_and_consts( |
| ty, |
| |e, _| match e { |
| Either::Left(ty) => Either::Left(match ty.kind(Interner) { |
| TyKind::Alias(AliasTy::Projection(proj_ty)) => { |
| self.normalize_projection_ty(proj_ty.clone()) |
| } |
| _ => ty, |
| }), |
| Either::Right(c) => Either::Right(match &c.data(Interner).value { |
| chalk_ir::ConstValue::Concrete(cc) => match &cc.interned { |
| crate::ConstScalar::UnevaluatedConst(c_id, subst) => { |
| // FIXME: Ideally here we should do everything that we do with type alias, i.e. adding a variable |
| // and registering an obligation. But it needs chalk support, so we handle the most basic |
| // case (a non associated const without generic parameters) manually. |
| if subst.len(Interner) == 0 { |
| if let Ok(eval) = self.db.const_eval(*c_id, subst.clone(), None) { |
| eval |
| } else { |
| unknown_const(c.data(Interner).ty.clone()) |
| } |
| } else { |
| unknown_const(c.data(Interner).ty.clone()) |
| } |
| } |
| _ => c, |
| }, |
| _ => c, |
| }), |
| }, |
| DebruijnIndex::INNERMOST, |
| ) |
| } |
| |
| pub(crate) fn normalize_projection_ty(&mut self, proj_ty: ProjectionTy) -> Ty { |
| let var = self.new_type_var(); |
| let alias_eq = AliasEq { alias: AliasTy::Projection(proj_ty), ty: var.clone() }; |
| let obligation = alias_eq.cast(Interner); |
| self.register_obligation(obligation); |
| var |
| } |
| |
| fn extend_type_variable_table(&mut self, to_index: usize) { |
| let count = to_index - self.type_variable_table.len() + 1; |
| self.type_variable_table.extend(iter::repeat(TypeVariableFlags::default()).take(count)); |
| } |
| |
| fn new_var(&mut self, kind: TyVariableKind, diverging: bool) -> Ty { |
| let var = self.var_unification_table.new_variable(UniverseIndex::ROOT); |
| // Chalk might have created some type variables for its own purposes that we don't know about... |
| self.extend_type_variable_table(var.index() as usize); |
| assert_eq!(var.index() as usize, self.type_variable_table.len() - 1); |
| let flags = self.type_variable_table.get_mut(var.index() as usize).unwrap(); |
| if diverging { |
| *flags |= TypeVariableFlags::DIVERGING; |
| } |
| if matches!(kind, TyVariableKind::Integer) { |
| *flags |= TypeVariableFlags::INTEGER; |
| } else if matches!(kind, TyVariableKind::Float) { |
| *flags |= TypeVariableFlags::FLOAT; |
| } |
| var.to_ty_with_kind(Interner, kind) |
| } |
| |
| pub(crate) fn new_type_var(&mut self) -> Ty { |
| self.new_var(TyVariableKind::General, false) |
| } |
| |
| pub(crate) fn new_integer_var(&mut self) -> Ty { |
| self.new_var(TyVariableKind::Integer, false) |
| } |
| |
| pub(crate) fn new_float_var(&mut self) -> Ty { |
| self.new_var(TyVariableKind::Float, false) |
| } |
| |
| pub(crate) fn new_maybe_never_var(&mut self) -> Ty { |
| self.new_var(TyVariableKind::General, true) |
| } |
| |
| pub(crate) fn new_const_var(&mut self, ty: Ty) -> Const { |
| let var = self.var_unification_table.new_variable(UniverseIndex::ROOT); |
| var.to_const(Interner, ty) |
| } |
| |
| pub(crate) fn new_lifetime_var(&mut self) -> Lifetime { |
| let var = self.var_unification_table.new_variable(UniverseIndex::ROOT); |
| var.to_lifetime(Interner) |
| } |
| |
| pub(crate) fn resolve_with_fallback<T>( |
| &mut self, |
| t: T, |
| fallback: &dyn Fn(InferenceVar, VariableKind, GenericArg, DebruijnIndex) -> GenericArg, |
| ) -> T |
| where |
| T: HasInterner<Interner = Interner> + TypeFoldable<Interner>, |
| { |
| self.resolve_with_fallback_inner(&mut Vec::new(), t, &fallback) |
| } |
| |
| pub(crate) fn fresh_subst(&mut self, binders: &[CanonicalVarKind<Interner>]) -> Substitution { |
| Substitution::from_iter( |
| Interner, |
| binders.iter().map(|kind| { |
| let param_infer_var = |
| kind.map_ref(|&ui| self.var_unification_table.new_variable(ui)); |
| param_infer_var.to_generic_arg(Interner) |
| }), |
| ) |
| } |
| |
| pub(crate) fn instantiate_canonical<T>(&mut self, canonical: Canonical<T>) -> T |
| where |
| T: HasInterner<Interner = Interner> + TypeFoldable<Interner> + std::fmt::Debug, |
| { |
| let subst = self.fresh_subst(canonical.binders.as_slice(Interner)); |
| subst.apply(canonical.value, Interner) |
| } |
| |
| fn resolve_with_fallback_inner<T>( |
| &mut self, |
| var_stack: &mut Vec<InferenceVar>, |
| t: T, |
| fallback: &dyn Fn(InferenceVar, VariableKind, GenericArg, DebruijnIndex) -> GenericArg, |
| ) -> T |
| where |
| T: HasInterner<Interner = Interner> + TypeFoldable<Interner>, |
| { |
| t.fold_with( |
| &mut resolve::Resolver { table: self, var_stack, fallback }, |
| DebruijnIndex::INNERMOST, |
| ) |
| } |
| |
| pub(crate) fn resolve_completely<T>(&mut self, t: T) -> T |
| where |
| T: HasInterner<Interner = Interner> + TypeFoldable<Interner>, |
| { |
| self.resolve_with_fallback(t, &|_, _, d, _| d) |
| } |
| |
| /// Apply a fallback to unresolved scalar types. Integer type variables and float type |
| /// variables are replaced with i32 and f64, respectively. |
| /// |
| /// This method is only intended to be called just before returning inference results (i.e. in |
| /// `InferenceContext::resolve_all()`). |
| /// |
| /// FIXME: This method currently doesn't apply fallback to unconstrained general type variables |
| /// whereas rustc replaces them with `()` or `!`. |
| pub(super) fn fallback_if_possible(&mut self) { |
| let int_fallback = TyKind::Scalar(Scalar::Int(IntTy::I32)).intern(Interner); |
| let float_fallback = TyKind::Scalar(Scalar::Float(FloatTy::F64)).intern(Interner); |
| |
| let scalar_vars: Vec<_> = self |
| .type_variable_table |
| .iter() |
| .enumerate() |
| .filter_map(|(index, flags)| { |
| let kind = if flags.contains(TypeVariableFlags::INTEGER) { |
| TyVariableKind::Integer |
| } else if flags.contains(TypeVariableFlags::FLOAT) { |
| TyVariableKind::Float |
| } else { |
| return None; |
| }; |
| |
| // FIXME: This is not really the nicest way to get `InferenceVar`s. Can we get them |
| // without directly constructing them from `index`? |
| let var = InferenceVar::from(index as u32).to_ty(Interner, kind); |
| Some(var) |
| }) |
| .collect(); |
| |
| for var in scalar_vars { |
| let maybe_resolved = self.resolve_ty_shallow(&var); |
| if let TyKind::InferenceVar(_, kind) = maybe_resolved.kind(Interner) { |
| let fallback = match kind { |
| TyVariableKind::Integer => &int_fallback, |
| TyVariableKind::Float => &float_fallback, |
| TyVariableKind::General => unreachable!(), |
| }; |
| self.unify(&var, fallback); |
| } |
| } |
| } |
| |
| /// Unify two relatable values (e.g. `Ty`) and register new trait goals that arise from that. |
| pub(crate) fn unify<T: ?Sized + Zip<Interner>>(&mut self, ty1: &T, ty2: &T) -> bool { |
| let result = match self.try_unify(ty1, ty2) { |
| Ok(r) => r, |
| Err(_) => return false, |
| }; |
| self.register_infer_ok(result); |
| true |
| } |
| |
| /// Unify two relatable values (e.g. `Ty`) and return new trait goals arising from it, so the |
| /// caller needs to deal with them. |
| pub(crate) fn try_unify<T: ?Sized + Zip<Interner>>( |
| &mut self, |
| t1: &T, |
| t2: &T, |
| ) -> InferResult<()> { |
| match self.var_unification_table.relate( |
| Interner, |
| &self.db, |
| &self.trait_env.env, |
| chalk_ir::Variance::Invariant, |
| t1, |
| t2, |
| ) { |
| Ok(result) => Ok(InferOk { goals: result.goals, value: () }), |
| Err(chalk_ir::NoSolution) => Err(TypeError), |
| } |
| } |
| |
| /// If `ty` is a type variable with known type, returns that type; |
| /// otherwise, return ty. |
| pub(crate) fn resolve_ty_shallow(&mut self, ty: &Ty) -> Ty { |
| self.resolve_obligations_as_possible(); |
| self.var_unification_table.normalize_ty_shallow(Interner, ty).unwrap_or_else(|| ty.clone()) |
| } |
| |
| pub(crate) fn snapshot(&mut self) -> InferenceTableSnapshot { |
| let var_table_snapshot = self.var_unification_table.snapshot(); |
| let type_variable_table_snapshot = self.type_variable_table.clone(); |
| let pending_obligations = self.pending_obligations.clone(); |
| InferenceTableSnapshot { |
| var_table_snapshot, |
| pending_obligations, |
| type_variable_table_snapshot, |
| } |
| } |
| |
| pub(crate) fn rollback_to(&mut self, snapshot: InferenceTableSnapshot) { |
| self.var_unification_table.rollback_to(snapshot.var_table_snapshot); |
| self.type_variable_table = snapshot.type_variable_table_snapshot; |
| self.pending_obligations = snapshot.pending_obligations; |
| } |
| |
| pub(crate) fn run_in_snapshot<T>(&mut self, f: impl FnOnce(&mut InferenceTable<'_>) -> T) -> T { |
| let snapshot = self.snapshot(); |
| let result = f(self); |
| self.rollback_to(snapshot); |
| result |
| } |
| |
| /// Checks an obligation without registering it. Useful mostly to check |
| /// whether a trait *might* be implemented before deciding to 'lock in' the |
| /// choice (during e.g. method resolution or deref). |
| pub(crate) fn try_obligation(&mut self, goal: Goal) -> Option<Solution> { |
| let in_env = InEnvironment::new(&self.trait_env.env, goal); |
| let canonicalized = self.canonicalize(in_env); |
| |
| self.db.trait_solve(self.trait_env.krate, self.trait_env.block, canonicalized.value) |
| } |
| |
| pub(crate) fn register_obligation(&mut self, goal: Goal) { |
| let in_env = InEnvironment::new(&self.trait_env.env, goal); |
| self.register_obligation_in_env(in_env) |
| } |
| |
| fn register_obligation_in_env(&mut self, goal: InEnvironment<Goal>) { |
| let canonicalized = self.canonicalize(goal); |
| if !self.try_resolve_obligation(&canonicalized) { |
| self.pending_obligations.push(canonicalized); |
| } |
| } |
| |
| pub(crate) fn register_infer_ok<T>(&mut self, infer_ok: InferOk<T>) { |
| infer_ok.goals.into_iter().for_each(|goal| self.register_obligation_in_env(goal)); |
| } |
| |
| pub(crate) fn resolve_obligations_as_possible(&mut self) { |
| let _span = profile::span("resolve_obligations_as_possible"); |
| let mut changed = true; |
| let mut obligations = mem::take(&mut self.resolve_obligations_buffer); |
| while mem::take(&mut changed) { |
| mem::swap(&mut self.pending_obligations, &mut obligations); |
| |
| for canonicalized in obligations.drain(..) { |
| if !self.check_changed(&canonicalized) { |
| self.pending_obligations.push(canonicalized); |
| continue; |
| } |
| changed = true; |
| let uncanonical = chalk_ir::Substitute::apply( |
| &canonicalized.free_vars, |
| canonicalized.value.value, |
| Interner, |
| ); |
| self.register_obligation_in_env(uncanonical); |
| } |
| } |
| self.resolve_obligations_buffer = obligations; |
| self.resolve_obligations_buffer.clear(); |
| } |
| |
| pub(crate) fn fudge_inference<T: TypeFoldable<Interner>>( |
| &mut self, |
| f: impl FnOnce(&mut Self) -> T, |
| ) -> T { |
| use chalk_ir::fold::TypeFolder; |
| |
| #[derive(chalk_derive::FallibleTypeFolder)] |
| #[has_interner(Interner)] |
| struct VarFudger<'a, 'b> { |
| table: &'a mut InferenceTable<'b>, |
| highest_known_var: InferenceVar, |
| } |
| impl TypeFolder<Interner> for VarFudger<'_, '_> { |
| fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner, Error = Self::Error> { |
| self |
| } |
| |
| fn interner(&self) -> Interner { |
| Interner |
| } |
| |
| fn fold_inference_ty( |
| &mut self, |
| var: chalk_ir::InferenceVar, |
| kind: TyVariableKind, |
| _outer_binder: chalk_ir::DebruijnIndex, |
| ) -> chalk_ir::Ty<Interner> { |
| if var < self.highest_known_var { |
| var.to_ty(Interner, kind) |
| } else { |
| self.table.new_type_var() |
| } |
| } |
| |
| fn fold_inference_lifetime( |
| &mut self, |
| var: chalk_ir::InferenceVar, |
| _outer_binder: chalk_ir::DebruijnIndex, |
| ) -> chalk_ir::Lifetime<Interner> { |
| if var < self.highest_known_var { |
| var.to_lifetime(Interner) |
| } else { |
| self.table.new_lifetime_var() |
| } |
| } |
| |
| fn fold_inference_const( |
| &mut self, |
| ty: chalk_ir::Ty<Interner>, |
| var: chalk_ir::InferenceVar, |
| _outer_binder: chalk_ir::DebruijnIndex, |
| ) -> chalk_ir::Const<Interner> { |
| if var < self.highest_known_var { |
| var.to_const(Interner, ty) |
| } else { |
| self.table.new_const_var(ty) |
| } |
| } |
| } |
| |
| let snapshot = self.snapshot(); |
| let highest_known_var = self.new_type_var().inference_var(Interner).expect("inference_var"); |
| let result = f(self); |
| self.rollback_to(snapshot); |
| result |
| .fold_with(&mut VarFudger { table: self, highest_known_var }, DebruijnIndex::INNERMOST) |
| } |
| |
| /// This checks whether any of the free variables in the `canonicalized` |
| /// have changed (either been unified with another variable, or with a |
| /// value). If this is not the case, we don't need to try to solve the goal |
| /// again -- it'll give the same result as last time. |
| fn check_changed(&mut self, canonicalized: &Canonicalized<InEnvironment<Goal>>) -> bool { |
| canonicalized.free_vars.iter().any(|var| { |
| let iv = match var.data(Interner) { |
| GenericArgData::Ty(ty) => ty.inference_var(Interner), |
| GenericArgData::Lifetime(lt) => lt.inference_var(Interner), |
| GenericArgData::Const(c) => c.inference_var(Interner), |
| } |
| .expect("free var is not inference var"); |
| if self.var_unification_table.probe_var(iv).is_some() { |
| return true; |
| } |
| let root = self.var_unification_table.inference_var_root(iv); |
| iv != root |
| }) |
| } |
| |
| fn try_resolve_obligation( |
| &mut self, |
| canonicalized: &Canonicalized<InEnvironment<Goal>>, |
| ) -> bool { |
| let solution = self.db.trait_solve( |
| self.trait_env.krate, |
| self.trait_env.block, |
| canonicalized.value.clone(), |
| ); |
| |
| match solution { |
| Some(Solution::Unique(canonical_subst)) => { |
| canonicalized.apply_solution( |
| self, |
| Canonical { |
| binders: canonical_subst.binders, |
| // FIXME: handle constraints |
| value: canonical_subst.value.subst, |
| }, |
| ); |
| true |
| } |
| Some(Solution::Ambig(Guidance::Definite(substs))) => { |
| canonicalized.apply_solution(self, substs); |
| false |
| } |
| Some(_) => { |
| // FIXME use this when trying to resolve everything at the end |
| false |
| } |
| None => { |
| // FIXME obligation cannot be fulfilled => diagnostic |
| true |
| } |
| } |
| } |
| |
| pub(crate) fn callable_sig( |
| &mut self, |
| ty: &Ty, |
| num_args: usize, |
| ) -> Option<(Option<FnTrait>, Vec<Ty>, Ty)> { |
| match ty.callable_sig(self.db) { |
| Some(sig) => Some((None, sig.params().to_vec(), sig.ret().clone())), |
| None => { |
| let (f, args_ty, return_ty) = self.callable_sig_from_fn_trait(ty, num_args)?; |
| Some((Some(f), args_ty, return_ty)) |
| } |
| } |
| } |
| |
| fn callable_sig_from_fn_trait( |
| &mut self, |
| ty: &Ty, |
| num_args: usize, |
| ) -> Option<(FnTrait, Vec<Ty>, Ty)> { |
| let krate = self.trait_env.krate; |
| let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?; |
| let trait_data = self.db.trait_data(fn_once_trait); |
| let output_assoc_type = trait_data.associated_type_by_name(&name![Output])?; |
| |
| let mut arg_tys = vec![]; |
| let arg_ty = TyBuilder::tuple(num_args) |
| .fill(|it| { |
| let arg = match it { |
| ParamKind::Type => self.new_type_var(), |
| ParamKind::Const(_) => unreachable!("Tuple with const parameter"), |
| }; |
| arg_tys.push(arg.clone()); |
| arg.cast(Interner) |
| }) |
| .build(); |
| |
| let projection = { |
| let b = TyBuilder::subst_for_def(self.db, fn_once_trait, None); |
| if b.remaining() != 2 { |
| return None; |
| } |
| let fn_once_subst = b.push(ty.clone()).push(arg_ty).build(); |
| |
| TyBuilder::assoc_type_projection(self.db, output_assoc_type, Some(fn_once_subst)) |
| .build() |
| }; |
| |
| let trait_env = self.trait_env.env.clone(); |
| let mut trait_ref = projection.trait_ref(self.db); |
| let obligation = InEnvironment { |
| goal: trait_ref.clone().cast(Interner), |
| environment: trait_env.clone(), |
| }; |
| let canonical = self.canonicalize(obligation.clone()); |
| if self |
| .db |
| .trait_solve(krate, self.trait_env.block, canonical.value.cast(Interner)) |
| .is_some() |
| { |
| self.register_obligation(obligation.goal); |
| let return_ty = self.normalize_projection_ty(projection); |
| for fn_x in [FnTrait::Fn, FnTrait::FnMut, FnTrait::FnOnce] { |
| let fn_x_trait = fn_x.get_id(self.db, krate)?; |
| trait_ref.trait_id = to_chalk_trait_id(fn_x_trait); |
| let obligation: chalk_ir::InEnvironment<chalk_ir::Goal<Interner>> = InEnvironment { |
| goal: trait_ref.clone().cast(Interner), |
| environment: trait_env.clone(), |
| }; |
| let canonical = self.canonicalize(obligation.clone()); |
| if self |
| .db |
| .trait_solve(krate, self.trait_env.block, canonical.value.cast(Interner)) |
| .is_some() |
| { |
| return Some((fn_x, arg_tys, return_ty)); |
| } |
| } |
| unreachable!("It should at least implement FnOnce at this point"); |
| } else { |
| None |
| } |
| } |
| |
| pub(super) fn insert_type_vars<T>(&mut self, ty: T) -> T |
| where |
| T: HasInterner<Interner = Interner> + TypeFoldable<Interner>, |
| { |
| fold_tys_and_consts( |
| ty, |
| |it, _| match it { |
| Either::Left(ty) => Either::Left(self.insert_type_vars_shallow(ty)), |
| Either::Right(c) => Either::Right(self.insert_const_vars_shallow(c)), |
| }, |
| DebruijnIndex::INNERMOST, |
| ) |
| } |
| |
| /// Replaces `Ty::Error` by a new type var, so we can maybe still infer it. |
| pub(super) fn insert_type_vars_shallow(&mut self, ty: Ty) -> Ty { |
| match ty.kind(Interner) { |
| TyKind::Error => self.new_type_var(), |
| TyKind::InferenceVar(..) => { |
| let ty_resolved = self.resolve_ty_shallow(&ty); |
| if ty_resolved.is_unknown() { |
| self.new_type_var() |
| } else { |
| ty |
| } |
| } |
| _ => ty, |
| } |
| } |
| |
| /// Replaces ConstScalar::Unknown by a new type var, so we can maybe still infer it. |
| pub(super) fn insert_const_vars_shallow(&mut self, c: Const) -> Const { |
| let data = c.data(Interner); |
| match &data.value { |
| ConstValue::Concrete(cc) => match &cc.interned { |
| crate::ConstScalar::Unknown => self.new_const_var(data.ty.clone()), |
| // try to evaluate unevaluated const. Replace with new var if const eval failed. |
| crate::ConstScalar::UnevaluatedConst(id, subst) => { |
| if let Ok(eval) = self.db.const_eval(*id, subst.clone(), None) { |
| eval |
| } else { |
| self.new_const_var(data.ty.clone()) |
| } |
| } |
| _ => c, |
| }, |
| _ => c, |
| } |
| } |
| } |
| |
| impl fmt::Debug for InferenceTable<'_> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("InferenceTable").field("num_vars", &self.type_variable_table.len()).finish() |
| } |
| } |
| |
| mod resolve { |
| use super::InferenceTable; |
| use crate::{ |
| ConcreteConst, Const, ConstData, ConstScalar, ConstValue, DebruijnIndex, GenericArg, |
| InferenceVar, Interner, Lifetime, Ty, TyVariableKind, VariableKind, |
| }; |
| use chalk_ir::{ |
| cast::Cast, |
| fold::{TypeFoldable, TypeFolder}, |
| }; |
| |
| #[derive(chalk_derive::FallibleTypeFolder)] |
| #[has_interner(Interner)] |
| pub(super) struct Resolver< |
| 'a, |
| 'b, |
| F: Fn(InferenceVar, VariableKind, GenericArg, DebruijnIndex) -> GenericArg, |
| > { |
| pub(super) table: &'a mut InferenceTable<'b>, |
| pub(super) var_stack: &'a mut Vec<InferenceVar>, |
| pub(super) fallback: F, |
| } |
| impl<F> TypeFolder<Interner> for Resolver<'_, '_, F> |
| where |
| F: Fn(InferenceVar, VariableKind, GenericArg, DebruijnIndex) -> GenericArg, |
| { |
| fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner, Error = Self::Error> { |
| self |
| } |
| |
| fn interner(&self) -> Interner { |
| Interner |
| } |
| |
| fn fold_inference_ty( |
| &mut self, |
| var: InferenceVar, |
| kind: TyVariableKind, |
| outer_binder: DebruijnIndex, |
| ) -> Ty { |
| let var = self.table.var_unification_table.inference_var_root(var); |
| if self.var_stack.contains(&var) { |
| // recursive type |
| let default = self.table.fallback_value(var, kind).cast(Interner); |
| return (self.fallback)(var, VariableKind::Ty(kind), default, outer_binder) |
| .assert_ty_ref(Interner) |
| .clone(); |
| } |
| let result = if let Some(known_ty) = self.table.var_unification_table.probe_var(var) { |
| // known_ty may contain other variables that are known by now |
| self.var_stack.push(var); |
| let result = known_ty.fold_with(self, outer_binder); |
| self.var_stack.pop(); |
| result.assert_ty_ref(Interner).clone() |
| } else { |
| let default = self.table.fallback_value(var, kind).cast(Interner); |
| (self.fallback)(var, VariableKind::Ty(kind), default, outer_binder) |
| .assert_ty_ref(Interner) |
| .clone() |
| }; |
| result |
| } |
| |
| fn fold_inference_const( |
| &mut self, |
| ty: Ty, |
| var: InferenceVar, |
| outer_binder: DebruijnIndex, |
| ) -> Const { |
| let var = self.table.var_unification_table.inference_var_root(var); |
| let default = ConstData { |
| ty: ty.clone(), |
| value: ConstValue::Concrete(ConcreteConst { interned: ConstScalar::Unknown }), |
| } |
| .intern(Interner) |
| .cast(Interner); |
| if self.var_stack.contains(&var) { |
| // recursive |
| return (self.fallback)(var, VariableKind::Const(ty), default, outer_binder) |
| .assert_const_ref(Interner) |
| .clone(); |
| } |
| if let Some(known_ty) = self.table.var_unification_table.probe_var(var) { |
| // known_ty may contain other variables that are known by now |
| self.var_stack.push(var); |
| let result = known_ty.fold_with(self, outer_binder); |
| self.var_stack.pop(); |
| result.assert_const_ref(Interner).clone() |
| } else { |
| (self.fallback)(var, VariableKind::Const(ty), default, outer_binder) |
| .assert_const_ref(Interner) |
| .clone() |
| } |
| } |
| |
| fn fold_inference_lifetime( |
| &mut self, |
| _var: InferenceVar, |
| _outer_binder: DebruijnIndex, |
| ) -> Lifetime { |
| // fall back all lifetimes to 'static -- currently we don't deal |
| // with any lifetimes, but we can sometimes get some lifetime |
| // variables through Chalk's unification, and this at least makes |
| // sure we don't leak them outside of inference |
| crate::static_lifetime() |
| } |
| } |
| } |
