Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/hir-ty/src/inhabitedness.rs')
| -rw-r--r-- | crates/hir-ty/src/inhabitedness.rs | 30 |
1 files changed, 23 insertions, 7 deletions
diff --git a/crates/hir-ty/src/inhabitedness.rs b/crates/hir-ty/src/inhabitedness.rs index 36af78153d..e5038543b6 100644 --- a/crates/hir-ty/src/inhabitedness.rs +++ b/crates/hir-ty/src/inhabitedness.rs @@ -6,9 +6,10 @@ use chalk_ir::{ DebruijnIndex, }; use hir_def::{ - adt::VariantData, attr::Attrs, visibility::Visibility, AdtId, EnumVariantId, HasModule, Lookup, - ModuleId, VariantId, + attr::Attrs, data::adt::VariantData, visibility::Visibility, AdtId, EnumVariantId, HasModule, + Lookup, ModuleId, VariantId, }; +use rustc_hash::FxHashSet; use crate::{ consteval::try_const_usize, db::HirDatabase, Binders, Interner, Substitution, Ty, TyKind, @@ -16,7 +17,8 @@ use crate::{ /// Checks whether a type is visibly uninhabited from a particular module. pub(crate) fn is_ty_uninhabited_from(ty: &Ty, target_mod: ModuleId, db: &dyn HirDatabase) -> bool { - let mut uninhabited_from = UninhabitedFrom { target_mod, db }; + let mut uninhabited_from = + UninhabitedFrom { target_mod, db, max_depth: 500, recursive_ty: FxHashSet::default() }; let inhabitedness = ty.visit_with(&mut uninhabited_from, DebruijnIndex::INNERMOST); inhabitedness == BREAK_VISIBLY_UNINHABITED } @@ -32,7 +34,8 @@ pub(crate) fn is_enum_variant_uninhabited_from( let vars_attrs = db.variants_attrs(variant.parent); let is_local = variant.parent.lookup(db.upcast()).container.krate() == target_mod.krate(); - let mut uninhabited_from = UninhabitedFrom { target_mod, db }; + let mut uninhabited_from = + UninhabitedFrom { target_mod, db, max_depth: 500, recursive_ty: FxHashSet::default() }; let inhabitedness = uninhabited_from.visit_variant( variant.into(), &enum_data.variants[variant.local_id].variant_data, @@ -45,6 +48,9 @@ pub(crate) fn is_enum_variant_uninhabited_from( struct UninhabitedFrom<'a> { target_mod: ModuleId, + recursive_ty: FxHashSet<Ty>, + // guard for preventing stack overflow in non trivial non terminating types + max_depth: usize, db: &'a dyn HirDatabase, } @@ -65,17 +71,27 @@ impl TypeVisitor<Interner> for UninhabitedFrom<'_> { ty: &Ty, outer_binder: DebruijnIndex, ) -> ControlFlow<VisiblyUninhabited> { - match ty.kind(Interner) { + if self.recursive_ty.contains(ty) || self.max_depth == 0 { + // rustc considers recursive types always inhabited. I think it is valid to consider + // recursive types as always uninhabited, but we should do what rustc is doing. + return CONTINUE_OPAQUELY_INHABITED; + } + self.recursive_ty.insert(ty.clone()); + self.max_depth -= 1; + let r = match ty.kind(Interner) { TyKind::Adt(adt, subst) => self.visit_adt(adt.0, subst), TyKind::Never => BREAK_VISIBLY_UNINHABITED, TyKind::Tuple(..) => ty.super_visit_with(self, outer_binder), - TyKind::Array(item_ty, len) => match try_const_usize(len) { + TyKind::Array(item_ty, len) => match try_const_usize(self.db, len) { Some(0) | None => CONTINUE_OPAQUELY_INHABITED, Some(1..) => item_ty.super_visit_with(self, outer_binder), }, TyKind::Ref(..) | _ => CONTINUE_OPAQUELY_INHABITED, - } + }; + self.recursive_ty.remove(ty); + self.max_depth += 1; + r } fn interner(&self) -> Interner { |