//! Methods for lowering the HIR to types. There are two main cases here:
//!
//! - Lowering a type reference like `&usize` or `Option<foo::bar::Baz>` to a
-//! type: The entry point for this is `Ty::from_hir`.
-//! - Building the type for an item: This happens through the `type_for_def` query.
+//! type: The entry point for this is `TyLoweringContext::lower_ty`.
+//! - Building the type for an item: This happens through the `ty` query.
//!
//! This usually involves resolving names, collecting generic arguments etc.
use std::{
- cell::{Cell, RefCell},
+ cell::{Cell, RefCell, RefMut},
iter,
sync::Arc,
};
consteval::{intern_const_scalar, path_to_const, unknown_const, unknown_const_as_generic},
db::HirDatabase,
make_binders,
- mapping::ToChalk,
+ mapping::{from_chalk_trait_id, ToChalk},
static_lifetime, to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
utils::Generics,
utils::{all_super_trait_refs, associated_type_by_name_including_super_traits, generics},
})
.intern(Interner)
}
- TypeRef::DynTrait(bounds) => {
- let self_ty =
- TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(Interner);
- let bounds = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
- QuantifiedWhereClauses::from_iter(
- Interner,
- bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)),
- )
- });
- let bounds = crate::make_single_type_binders(bounds);
- TyKind::Dyn(DynTy { bounds, lifetime: static_lifetime() }).intern(Interner)
- }
+ TypeRef::DynTrait(bounds) => self.lower_dyn_trait(bounds),
TypeRef::ImplTrait(bounds) => {
match self.impl_trait_mode {
ImplTraitLoweringMode::Opaque => {
}
}
TypeRef::Macro(macro_call) => {
- let (expander, recursion_start) = {
- let mut expander = self.expander.borrow_mut();
- if expander.is_some() {
- (Some(expander), false)
- } else {
- *expander = Some(Expander::new(
- self.db.upcast(),
- macro_call.file_id,
- self.resolver.module(),
- ));
- (Some(expander), true)
+ let (mut expander, recursion_start) = {
+ match RefMut::filter_map(self.expander.borrow_mut(), Option::as_mut) {
+ // There already is an expander here, this means we are already recursing
+ Ok(expander) => (expander, false),
+ // No expander was created yet, so we are at the start of the expansion recursion
+ // and therefore have to create an expander.
+ Err(expander) => (
+ RefMut::map(expander, |it| {
+ it.insert(Expander::new(
+ self.db.upcast(),
+ macro_call.file_id,
+ self.resolver.module(),
+ ))
+ }),
+ true,
+ ),
}
};
- let ty = if let Some(mut expander) = expander {
- let expander_mut = expander.as_mut().unwrap();
+ let ty = {
let macro_call = macro_call.to_node(self.db.upcast());
- match expander
_mut.enter_expand::<ast::Type>(self.db.upcast(), macro_call) {
+ match expander.enter_expand::<ast::Type>(self.db.upcast(), macro_call) {
Ok(ExpandResult { value: Some((mark, expanded)), .. }) => {
- let ctx =
- LowerCtx::new(self.db.upcast(), expander_mut.current_file_id());
+ let ctx = LowerCtx::new(self.db.upcast(), expander.current_file_id());
let type_ref = TypeRef::from_ast(&ctx, expanded);
drop(expander);
.exit(self.db.upcast(), mark);
Some(ty)
}
- _ => None,
+ _ => {
+ drop(expander);
+ None
+ }
}
- } else {
- None
};
+
+ // drop the expander, resetting it to pre-recursion state
if recursion_start {
*self.expander.borrow_mut() = None;
}
}
}
0 => {
- let self_ty = Some(
- TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
- .intern(Interner),
- );
- let trait_ref = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
- ctx.lower_trait_ref_from_resolved_path(
- trait_,
- resolved_segment,
- self_ty,
- )
- });
- let dyn_ty = DynTy {
- bounds: crate::make_single_type_binders(
- QuantifiedWhereClauses::from_iter(
- Interner,
- Some(crate::wrap_empty_binders(WhereClause::Implemented(
- trait_ref,
- ))),
- ),
- ),
- lifetime: static_lifetime(),
- };
- TyKind::Dyn(dyn_ty).intern(Interner)
+ // Trait object type without dyn; this should be handled in upstream. See
+ // `lower_path()`.
+ stdx::never!("unexpected fully resolved trait path");
+ TyKind::Error.intern(Interner)
}
_ => {
// FIXME report error (ambiguous associated type)
TyKind::Placeholder(to_placeholder_idx(self.db, param_id.into()))
}
ParamLoweringMode::Variable => {
- let idx = generics.param_idx(param_id.into()).expect("matching generics");
+ let idx = match generics.param_idx(param_id.into()) {
+ None => {
+ never!("no matching generics");
+ return (TyKind::Error.intern(Interner), None);
+ }
+ Some(idx) => idx,
+ };
+
TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
}
}
let (ty, res) = self.lower_ty_ext(type_ref);
return self.lower_ty_relative_path(ty, res, path.segments());
}
+
let (resolution, remaining_index) =
match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
Some(it) => it,
None => return (TyKind::Error.intern(Interner), None),
};
+
+ if matches!(resolution, TypeNs::TraitId(_)) && remaining_index.is_none() {
+ // trait object type without dyn
+ let bound = TypeBound::Path(path.clone(), TraitBoundModifier::None);
+ let ty = self.lower_dyn_trait(&[Interned::new(bound)]);
+ return (ty, None);
+ }
+
let (resolved_segment, remaining_segments) = match remaining_index {
None => (
path.segments().last().expect("resolved path has at least one element"),
})
}
+ fn lower_dyn_trait(&self, bounds: &[Interned<TypeBound>]) -> Ty {
+ let self_ty = TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(Interner);
+ // INVARIANT: The principal trait bound must come first. Others may be in any order but
+ // should be in the same order for the same set but possibly different order of bounds in
+ // the input.
+ // This invariant is used by `TyExt::dyn_trait()` and chalk.
+ let bounds = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
+ let mut bounds: Vec<_> = bounds
+ .iter()
+ .flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false))
+ .collect();
+
+ let mut multiple_regular_traits = false;
+ let mut multiple_same_projection = false;
+ bounds.sort_unstable_by(|lhs, rhs| {
+ use std::cmp::Ordering;
+ match (lhs.skip_binders(), rhs.skip_binders()) {
+ (WhereClause::Implemented(lhs), WhereClause::Implemented(rhs)) => {
+ let lhs_id = lhs.trait_id;
+ let lhs_is_auto = ctx.db.trait_data(from_chalk_trait_id(lhs_id)).is_auto;
+ let rhs_id = rhs.trait_id;
+ let rhs_is_auto = ctx.db.trait_data(from_chalk_trait_id(rhs_id)).is_auto;
+
+ if !lhs_is_auto && !rhs_is_auto {
+ multiple_regular_traits = true;
+ }
+ // Note that the ordering here is important; this ensures the invariant
+ // mentioned above.
+ (lhs_is_auto, lhs_id).cmp(&(rhs_is_auto, rhs_id))
+ }
+ (WhereClause::Implemented(_), _) => Ordering::Less,
+ (_, WhereClause::Implemented(_)) => Ordering::Greater,
+ (WhereClause::AliasEq(lhs), WhereClause::AliasEq(rhs)) => {
+ match (&lhs.alias, &rhs.alias) {
+ (AliasTy::Projection(lhs_proj), AliasTy::Projection(rhs_proj)) => {
+ // We only compare the `associated_ty_id`s. We shouldn't have
+ // multiple bounds for an associated type in the correct Rust code,
+ // and if we do, we error out.
+ if lhs_proj.associated_ty_id == rhs_proj.associated_ty_id {
+ multiple_same_projection = true;
+ }
+ lhs_proj.associated_ty_id.cmp(&rhs_proj.associated_ty_id)
+ }
+ // We don't produce `AliasTy::Opaque`s yet.
+ _ => unreachable!(),
+ }
+ }
+ // We don't produce `WhereClause::{TypeOutlives, LifetimeOutlives}` yet.
+ _ => unreachable!(),
+ }
+ });
+
+ if multiple_regular_traits || multiple_same_projection {
+ return None;
+ }
+
+ // As multiple occurrences of the same auto traits *are* permitted, we dedulicate the
+ // bounds. We shouldn't have repeated elements besides auto traits at this point.
+ bounds.dedup();
+
+ Some(QuantifiedWhereClauses::from_iter(Interner, bounds))
+ });
+
+ if let Some(bounds) = bounds {
+ let bounds = crate::make_single_type_binders(bounds);
+ TyKind::Dyn(DynTy { bounds, lifetime: static_lifetime() }).intern(Interner)
+ } else {
+ // FIXME: report error (additional non-auto traits or associated type rebound)
+ TyKind::Error.intern(Interner)
+ }
+ }
+
fn lower_impl_trait(
&self,
bounds: &[Interned<TypeBound>],
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