//! 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.
//!
//! This usually involves resolving names, collecting generic arguments etc.
use std::{iter, sync::Arc};
use base_db::CrateId;
use chalk_ir::{cast::Cast, Mutability, Safety};
use hir_def::{
adt::StructKind,
builtin_type::BuiltinType,
generics::{TypeParamProvenance, WherePredicate, WherePredicateTypeTarget},
path::{GenericArg, Path, PathSegment, PathSegments},
resolver::{HasResolver, Resolver, TypeNs},
type_ref::{TypeBound, TypeRef},
AdtId, AssocContainerId, AssocItemId, ConstId, ConstParamId, EnumId, EnumVariantId, FunctionId,
GenericDefId, HasModule, ImplId, LocalFieldId, Lookup, StaticId, StructId, TraitId,
TypeAliasId, TypeParamId, UnionId, VariantId,
};
use hir_expand::name::Name;
use la_arena::ArenaMap;
use smallvec::SmallVec;
use stdx::impl_from;
use crate::{
db::HirDatabase,
to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
traits::chalk::{Interner, ToChalk},
utils::{
all_super_trait_refs, associated_type_by_name_including_super_traits, generics,
variant_data,
},
AliasEq, AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, FnPointer, FnSig,
GenericPredicate, ImplTraitId, OpaqueTy, PolyFnSig, ProjectionTy, ReturnTypeImplTrait,
ReturnTypeImplTraits, Substitution, TraitEnvironment, TraitRef, Ty, TyKind, TypeWalk,
};
#[derive(Debug)]
pub struct TyLoweringContext<'a> {
pub db: &'a dyn HirDatabase,
pub resolver: &'a Resolver,
in_binders: DebruijnIndex,
/// Note: Conceptually, it's thinkable that we could be in a location where
/// some type params should be represented as placeholders, and others
/// should be converted to variables. I think in practice, this isn't
/// possible currently, so this should be fine for now.
pub type_param_mode: TypeParamLoweringMode,
pub impl_trait_mode: ImplTraitLoweringMode,
impl_trait_counter: std::cell::Cell<u16>,
/// When turning `impl Trait` into opaque types, we have to collect the
/// bounds at the same time to get the IDs correct (without becoming too
/// complicated). I don't like using interior mutability (as for the
/// counter), but I've tried and failed to make the lifetimes work for
/// passing around a `&mut TyLoweringContext`. The core problem is that
/// we're grouping the mutable data (the counter and this field) together
/// with the immutable context (the references to the DB and resolver).
/// Splitting this up would be a possible fix.
opaque_type_data: std::cell::RefCell<Vec<ReturnTypeImplTrait>>,
}
impl<'a> TyLoweringContext<'a> {
pub fn new(db: &'a dyn HirDatabase, resolver: &'a Resolver) -> Self {
let impl_trait_counter = std::cell::Cell::new(0);
let impl_trait_mode = ImplTraitLoweringMode::Disallowed;
let type_param_mode = TypeParamLoweringMode::Placeholder;
let in_binders = DebruijnIndex::INNERMOST;
let opaque_type_data = std::cell::RefCell::new(Vec::new());
Self {
db,
resolver,
in_binders,
impl_trait_mode,
impl_trait_counter,
type_param_mode,
opaque_type_data,
}
}
pub fn with_debruijn<T>(
&self,
debruijn: DebruijnIndex,
f: impl FnOnce(&TyLoweringContext) -> T,
) -> T {
let opaque_ty_data_vec = self.opaque_type_data.replace(Vec::new());
let new_ctx = Self {
in_binders: debruijn,
impl_trait_counter: std::cell::Cell::new(self.impl_trait_counter.get()),
opaque_type_data: std::cell::RefCell::new(opaque_ty_data_vec),
..*self
};
let result = f(&new_ctx);
self.impl_trait_counter.set(new_ctx.impl_trait_counter.get());
self.opaque_type_data.replace(new_ctx.opaque_type_data.into_inner());
result
}
pub fn with_shifted_in<T>(
&self,
debruijn: DebruijnIndex,
f: impl FnOnce(&TyLoweringContext) -> T,
) -> T {
self.with_debruijn(self.in_binders.shifted_in_from(debruijn), f)
}
pub fn with_impl_trait_mode(self, impl_trait_mode: ImplTraitLoweringMode) -> Self {
Self { impl_trait_mode, ..self }
}
pub fn with_type_param_mode(self, type_param_mode: TypeParamLoweringMode) -> Self {
Self { type_param_mode, ..self }
}
}
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum ImplTraitLoweringMode {
/// `impl Trait` gets lowered into an opaque type that doesn't unify with
/// anything except itself. This is used in places where values flow 'out',
/// i.e. for arguments of the function we're currently checking, and return
/// types of functions we're calling.
Opaque,
/// `impl Trait` gets lowered into a type variable. Used for argument
/// position impl Trait when inside the respective function, since it allows
/// us to support that without Chalk.
Param,
/// `impl Trait` gets lowered into a variable that can unify with some
/// type. This is used in places where values flow 'in', i.e. for arguments
/// of functions we're calling, and the return type of the function we're
/// currently checking.
Variable,
/// `impl Trait` is disallowed and will be an error.
Disallowed,
}
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum TypeParamLoweringMode {
Placeholder,
Variable,
}
impl<'a> TyLoweringContext<'a> {
pub fn lower_ty(&self, type_ref: &TypeRef) -> Ty {
self.lower_ty_ext(type_ref).0
}
fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
let mut res = None;
let ty = match type_ref {
TypeRef::Never => TyKind::Never.intern(&Interner),
TypeRef::Tuple(inner) => {
let inner_tys = inner.iter().map(|tr| self.lower_ty(tr));
TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys))
.intern(&Interner)
}
TypeRef::Path(path) => {
let (ty, res_) = self.lower_path(path);
res = res_;
ty
}
TypeRef::RawPtr(inner, mutability) => {
let inner_ty = self.lower_ty(inner);
TyKind::Raw(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner)
}
TypeRef::Array(inner) => {
let inner_ty = self.lower_ty(inner);
TyKind::Array(inner_ty).intern(&Interner)
}
TypeRef::Slice(inner) => {
let inner_ty = self.lower_ty(inner);
TyKind::Slice(inner_ty).intern(&Interner)
}
TypeRef::Reference(inner, _, mutability) => {
let inner_ty = self.lower_ty(inner);
TyKind::Ref(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner)
}
TypeRef::Placeholder => TyKind::Unknown.intern(&Interner),
TypeRef::Fn(params, is_varargs) => {
let substs = Substitution(params.iter().map(|tr| self.lower_ty(tr)).collect());
TyKind::Function(FnPointer {
num_args: substs.len() - 1,
sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs },
substs,
})
.intern(&Interner)
}
TypeRef::DynTrait(bounds) => {
let self_ty =
TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone())).collect()
});
TyKind::Dyn(predicates).intern(&Interner)
}
TypeRef::ImplTrait(bounds) => {
match self.impl_trait_mode {
ImplTraitLoweringMode::Opaque => {
let idx = self.impl_trait_counter.get();
self.impl_trait_counter.set(idx + 1);
assert!(idx as usize == self.opaque_type_data.borrow().len());
// this dance is to make sure the data is in the right
// place even if we encounter more opaque types while
// lowering the bounds
self.opaque_type_data
.borrow_mut()
.push(ReturnTypeImplTrait { bounds: Binders::new(1, Vec::new()) });
// We don't want to lower the bounds inside the binders
// we're currently in, because they don't end up inside
// those binders. E.g. when we have `impl Trait<impl
// OtherTrait<T>>`, the `impl OtherTrait<T>` can't refer
// to the self parameter from `impl Trait`, and the
// bounds aren't actually stored nested within each
// other, but separately. So if the `T` refers to a type
// parameter of the outer function, it's just one binder
// away instead of two.
let actual_opaque_type_data = self
.with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
ctx.lower_impl_trait(&bounds)
});
self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
let func = match self.resolver.generic_def() {
Some(GenericDefId::FunctionId(f)) => f,
_ => panic!("opaque impl trait lowering in non-function"),
};
let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
let generics = generics(self.db.upcast(), func.into());
let parameters = Substitution::bound_vars(&generics, self.in_binders);
TyKind::Alias(AliasTy::Opaque(OpaqueTy {
opaque_ty_id,
substitution: parameters,
}))
.intern(&Interner)
}
ImplTraitLoweringMode::Param => {
let idx = self.impl_trait_counter.get();
// FIXME we're probably doing something wrong here
self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
if let Some(def) = self.resolver.generic_def() {
let generics = generics(self.db.upcast(), def);
let param = generics
.iter()
.filter(|(_, data)| {
data.provenance == TypeParamProvenance::ArgumentImplTrait
})
.nth(idx as usize)
.map_or(TyKind::Unknown, |(id, _)| {
TyKind::Placeholder(to_placeholder_idx(self.db, id))
});
param.intern(&Interner)
} else {
TyKind::Unknown.intern(&Interner)
}
}
ImplTraitLoweringMode::Variable => {
let idx = self.impl_trait_counter.get();
// FIXME we're probably doing something wrong here
self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
let (parent_params, self_params, list_params, _impl_trait_params) =
if let Some(def) = self.resolver.generic_def() {
let generics = generics(self.db.upcast(), def);
generics.provenance_split()
} else {
(0, 0, 0, 0)
};
TyKind::BoundVar(BoundVar::new(
self.in_binders,
idx as usize + parent_params + self_params + list_params,
))
.intern(&Interner)
}
ImplTraitLoweringMode::Disallowed => {
// FIXME: report error
TyKind::Unknown.intern(&Interner)
}
}
}
TypeRef::Error => TyKind::Unknown.intern(&Interner),
};
(ty, res)
}
/// This is only for `generic_predicates_for_param`, where we can't just
/// lower the self types of the predicates since that could lead to cycles.
/// So we just check here if the `type_ref` resolves to a generic param, and which.
fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option<TypeParamId> {
let path = match type_ref {
TypeRef::Path(path) => path,
_ => return None,
};
if path.type_anchor().is_some() {
return None;
}
if path.segments().len() > 1 {
return None;
}
let resolution =
match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
Some((it, None)) => it,
_ => return None,
};
if let TypeNs::GenericParam(param_id) = resolution {
Some(param_id)
} else {
None
}
}
pub(crate) fn lower_ty_relative_path(
&self,
ty: Ty,
// We need the original resolution to lower `Self::AssocTy` correctly
res: Option<TypeNs>,
remaining_segments: PathSegments<'_>,
) -> (Ty, Option<TypeNs>) {
if remaining_segments.len() == 1 {
// resolve unselected assoc types
let segment = remaining_segments.first().unwrap();
(self.select_associated_type(res, segment), None)
} else if remaining_segments.len() > 1 {
// FIXME report error (ambiguous associated type)
(TyKind::Unknown.intern(&Interner), None)
} else {
(ty, res)
}
}
pub(crate) fn lower_partly_resolved_path(
&self,
resolution: TypeNs,
resolved_segment: PathSegment<'_>,
remaining_segments: PathSegments<'_>,
infer_args: bool,
) -> (Ty, Option<TypeNs>) {
let ty = match resolution {
TypeNs::TraitId(trait_) => {
// if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
let self_ty = if remaining_segments.len() == 0 {
Some(
TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
.intern(&Interner),
)
} else {
None
};
let trait_ref =
self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty);
let ty = if remaining_segments.len() == 1 {
let segment = remaining_segments.first().unwrap();
let found = associated_type_by_name_including_super_traits(
self.db,
trait_ref,
&segment.name,
);
match found {
Some((super_trait_ref, associated_ty)) => {
// FIXME handle type parameters on the segment
TyKind::Alias(AliasTy::Projection(ProjectionTy {
associated_ty_id: to_assoc_type_id(associated_ty),
substitution: super_trait_ref.substitution,
}))
.intern(&Interner)
}
None => {
// FIXME: report error (associated type not found)
TyKind::Unknown.intern(&Interner)
}
}
} else if remaining_segments.len() > 1 {
// FIXME report error (ambiguous associated type)
TyKind::Unknown.intern(&Interner)
} else {
TyKind::Dyn(Arc::new([GenericPredicate::Implemented(trait_ref)]))
.intern(&Interner)
};
return (ty, None);
}
TypeNs::GenericParam(param_id) => {
let generics = generics(
self.db.upcast(),
self.resolver.generic_def().expect("generics in scope"),
);
match self.type_param_mode {
TypeParamLoweringMode::Placeholder => {
TyKind::Placeholder(to_placeholder_idx(self.db, param_id))
}
TypeParamLoweringMode::Variable => {
let idx = generics.param_idx(param_id).expect("matching generics");
TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
}
}
.intern(&Interner)
}
TypeNs::SelfType(impl_id) => {
let generics = generics(self.db.upcast(), impl_id.into());
let substs = match self.type_param_mode {
TypeParamLoweringMode::Placeholder => {
Substitution::type_params_for_generics(self.db, &generics)
}
TypeParamLoweringMode::Variable => {
Substitution::bound_vars(&generics, self.in_binders)
}
};
self.db.impl_self_ty(impl_id).subst(&substs)
}
TypeNs::AdtSelfType(adt) => {
let generics = generics(self.db.upcast(), adt.into());
let substs = match self.type_param_mode {
TypeParamLoweringMode::Placeholder => {
Substitution::type_params_for_generics(self.db, &generics)
}
TypeParamLoweringMode::Variable => {
Substitution::bound_vars(&generics, self.in_binders)
}
};
self.db.ty(adt.into()).subst(&substs)
}
TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
TypeNs::BuiltinType(it) => {
self.lower_path_inner(resolved_segment, it.into(), infer_args)
}
TypeNs::TypeAliasId(it) => {
self.lower_path_inner(resolved_segment, it.into(), infer_args)
}
// FIXME: report error
TypeNs::EnumVariantId(_) => return (TyKind::Unknown.intern(&Interner), None),
};
self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
}
pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option<TypeNs>) {
// Resolve the path (in type namespace)
if let Some(type_ref) = path.type_anchor() {
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::Unknown.intern(&Interner), None),
};
let (resolved_segment, remaining_segments) = match remaining_index {
None => (
path.segments().last().expect("resolved path has at least one element"),
PathSegments::EMPTY,
),
Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
};
self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false)
}
fn select_associated_type(&self, res: Option<TypeNs>, segment: PathSegment<'_>) -> Ty {
if let Some(res) = res {
let ty = associated_type_shorthand_candidates(
self.db,
res,
move |name, t, associated_ty| {
if name == segment.name {
let substs = match self.type_param_mode {
TypeParamLoweringMode::Placeholder => {
// if we're lowering to placeholders, we have to put
// them in now
let s = Substitution::type_params(
self.db,
self.resolver.generic_def().expect(
"there should be generics if there's a generic param",
),
);
t.substitution.clone().subst_bound_vars(&s)
}
TypeParamLoweringMode::Variable => t.substitution.clone(),
};
// We need to shift in the bound vars, since
// associated_type_shorthand_candidates does not do that
let substs = substs.shift_bound_vars(self.in_binders);
// FIXME handle type parameters on the segment
return Some(
TyKind::Alias(AliasTy::Projection(ProjectionTy {
associated_ty_id: to_assoc_type_id(associated_ty),
substitution: substs,
}))
.intern(&Interner),
);
}
None
},
);
ty.unwrap_or(TyKind::Unknown.intern(&Interner))
} else {
TyKind::Unknown.intern(&Interner)
}
}
fn lower_path_inner(
&self,
segment: PathSegment<'_>,
typeable: TyDefId,
infer_args: bool,
) -> Ty {
let generic_def = match typeable {
TyDefId::BuiltinType(_) => None,
TyDefId::AdtId(it) => Some(it.into()),
TyDefId::TypeAliasId(it) => Some(it.into()),
};
let substs = self.substs_from_path_segment(segment, generic_def, infer_args);
self.db.ty(typeable).subst(&substs)
}
/// Collect generic arguments from a path into a `Substs`. See also
/// `create_substs_for_ast_path` and `def_to_ty` in rustc.
pub(super) fn substs_from_path(
&self,
path: &Path,
// Note that we don't call `db.value_type(resolved)` here,
// `ValueTyDefId` is just a convenient way to pass generics and
// special-case enum variants
resolved: ValueTyDefId,
infer_args: bool,
) -> Substitution {
let last = path.segments().last().expect("path should have at least one segment");
let (segment, generic_def) = match resolved {
ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
ValueTyDefId::StructId(it) => (last, Some(it.into())),
ValueTyDefId::UnionId(it) => (last, Some(it.into())),
ValueTyDefId::ConstId(it) => (last, Some(it.into())),
ValueTyDefId::StaticId(_) => (last, None),
ValueTyDefId::EnumVariantId(var) => {
// the generic args for an enum variant may be either specified
// on the segment referring to the enum, or on the segment
// referring to the variant. So `Option::<T>::None` and
// `Option::None::<T>` are both allowed (though the former is
// preferred). See also `def_ids_for_path_segments` in rustc.
let len = path.segments().len();
let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None };
let segment = match penultimate {
Some(segment) if segment.args_and_bindings.is_some() => segment,
_ => last,
};
(segment, Some(var.parent.into()))
}
};
self.substs_from_path_segment(segment, generic_def, infer_args)
}
fn substs_from_path_segment(
&self,
segment: PathSegment<'_>,
def_generic: Option<GenericDefId>,
infer_args: bool,
) -> Substitution {
let mut substs = Vec::new();
let def_generics = def_generic.map(|def| generics(self.db.upcast(), def));
let (parent_params, self_params, type_params, impl_trait_params) =
def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
let total_len = parent_params + self_params + type_params + impl_trait_params;
substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(parent_params));
let mut had_explicit_type_args = false;
if let Some(generic_args) = &segment.args_and_bindings {
if !generic_args.has_self_type {
substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(self_params));
}
let expected_num =
if generic_args.has_self_type { self_params + type_params } else { type_params };
let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
// if args are provided, it should be all of them, but we can't rely on that
for arg in generic_args
.args
.iter()
.filter(|arg| matches!(arg, GenericArg::Type(_)))
.skip(skip)
.take(expected_num)
{
match arg {
GenericArg::Type(type_ref) => {
had_explicit_type_args = true;
let ty = self.lower_ty(type_ref);
substs.push(ty);
}
GenericArg::Lifetime(_) => {}
}
}
}
// handle defaults. In expression or pattern path segments without
// explicitly specified type arguments, missing type arguments are inferred
// (i.e. defaults aren't used).
if !infer_args || had_explicit_type_args {
if let Some(def_generic) = def_generic {
let defaults = self.db.generic_defaults(def_generic);
assert_eq!(total_len, defaults.len());
for default_ty in defaults.iter().skip(substs.len()) {
// each default can depend on the previous parameters
let substs_so_far = Substitution(substs.clone().into());
substs.push(default_ty.clone().subst(&substs_so_far));
}
}
}
// add placeholders for args that were not provided
// FIXME: emit diagnostics in contexts where this is not allowed
for _ in substs.len()..total_len {
substs.push(TyKind::Unknown.intern(&Interner));
}
assert_eq!(substs.len(), total_len);
Substitution(substs.into())
}
fn lower_trait_ref_from_path(
&self,
path: &Path,
explicit_self_ty: Option<Ty>,
) -> Option<TraitRef> {
let resolved =
match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? {
TypeNs::TraitId(tr) => tr,
_ => return None,
};
let segment = path.segments().last().expect("path should have at least one segment");
Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty))
}
pub(crate) fn lower_trait_ref_from_resolved_path(
&self,
resolved: TraitId,
segment: PathSegment<'_>,
explicit_self_ty: Option<Ty>,
) -> TraitRef {
let mut substs = self.trait_ref_substs_from_path(segment, resolved);
if let Some(self_ty) = explicit_self_ty {
substs.0[0] = self_ty;
}
TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs }
}
fn lower_trait_ref(
&self,
type_ref: &TypeRef,
explicit_self_ty: Option<Ty>,
) -> Option<TraitRef> {
let path = match type_ref {
TypeRef::Path(path) => path,
_ => return None,
};
self.lower_trait_ref_from_path(path, explicit_self_ty)
}
fn trait_ref_substs_from_path(
&self,
segment: PathSegment<'_>,
resolved: TraitId,
) -> Substitution {
self.substs_from_path_segment(segment, Some(resolved.into()), false)
}
pub(crate) fn lower_where_predicate(
&'a self,
where_predicate: &'a WherePredicate,
) -> impl Iterator<Item = GenericPredicate> + 'a {
match where_predicate {
WherePredicate::ForLifetime { target, bound, .. }
| WherePredicate::TypeBound { target, bound } => {
let self_ty = match target {
WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref),
WherePredicateTypeTarget::TypeParam(param_id) => {
let generic_def = self.resolver.generic_def().expect("generics in scope");
let generics = generics(self.db.upcast(), generic_def);
let param_id =
hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
let placeholder = to_placeholder_idx(self.db, param_id);
match self.type_param_mode {
TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
TypeParamLoweringMode::Variable => {
let idx = generics.param_idx(param_id).expect("matching generics");
TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
}
}
.intern(&Interner)
}
};
self.lower_type_bound(bound, self_ty).collect::<Vec<_>>().into_iter()
}
WherePredicate::Lifetime { .. } => vec![].into_iter(),
}
}
pub(crate) fn lower_type_bound(
&'a self,
bound: &'a TypeBound,
self_ty: Ty,
) -> impl Iterator<Item = GenericPredicate> + 'a {
let mut bindings = None;
let trait_ref = match bound {
TypeBound::Path(path) => {
bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
Some(
bindings.clone().map_or(GenericPredicate::Error, GenericPredicate::Implemented),
)
}
TypeBound::Lifetime(_) => None,
TypeBound::Error => Some(GenericPredicate::Error),
};
trait_ref.into_iter().chain(
bindings
.into_iter()
.flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)),
)
}
fn assoc_type_bindings_from_type_bound(
&'a self,
bound: &'a TypeBound,
trait_ref: TraitRef,
) -> impl Iterator<Item = GenericPredicate> + 'a {
let last_segment = match bound {
TypeBound::Path(path) => path.segments().last(),
TypeBound::Error | TypeBound::Lifetime(_) => None,
};
last_segment
.into_iter()
.flat_map(|segment| segment.args_and_bindings.into_iter())
.flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
.flat_map(move |binding| {
let found = associated_type_by_name_including_super_traits(
self.db,
trait_ref.clone(),
&binding.name,
);
let (super_trait_ref, associated_ty) = match found {
None => return SmallVec::<[GenericPredicate; 1]>::new(),
Some(t) => t,
};
let projection_ty = ProjectionTy {
associated_ty_id: to_assoc_type_id(associated_ty),
substitution: super_trait_ref.substitution,
};
let mut preds = SmallVec::with_capacity(
binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
);
if let Some(type_ref) = &binding.type_ref {
let ty = self.lower_ty(type_ref);
let alias_eq =
AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
preds.push(GenericPredicate::AliasEq(alias_eq));
}
for bound in &binding.bounds {
preds.extend(self.lower_type_bound(
bound,
TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner),
));
}
preds
})
}
fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
cov_mark::hit!(lower_rpit);
let self_ty =
TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone())).collect()
});
ReturnTypeImplTrait { bounds: Binders::new(1, predicates) }
}
}
fn count_impl_traits(type_ref: &TypeRef) -> usize {
let mut count = 0;
type_ref.walk(&mut |type_ref| {
if matches!(type_ref, TypeRef::ImplTrait(_)) {
count += 1;
}
});
count
}
/// Build the signature of a callable item (function, struct or enum variant).
pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig {
match def {
CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f),
CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s),
CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e),
}
}
pub fn associated_type_shorthand_candidates<R>(
db: &dyn HirDatabase,
res: TypeNs,
mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
) -> Option<R> {
let traits_from_env: Vec<_> = match res {
TypeNs::SelfType(impl_id) => match db.impl_trait(impl_id) {
None => vec![],
Some(trait_ref) => vec![trait_ref.value],
},
TypeNs::GenericParam(param_id) => {
let predicates = db.generic_predicates_for_param(param_id);
let mut traits_: Vec<_> = predicates
.iter()
.filter_map(|pred| match &pred.value {
GenericPredicate::Implemented(tr) => Some(tr.clone()),
_ => None,
})
.collect();
// Handle `Self::Type` referring to own associated type in trait definitions
if let GenericDefId::TraitId(trait_id) = param_id.parent {
let generics = generics(db.upcast(), trait_id.into());
if generics.params.types[param_id.local_id].provenance
== TypeParamProvenance::TraitSelf
{
let trait_ref = TraitRef {
trait_id: to_chalk_trait_id(trait_id),
substitution: Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST),
};
traits_.push(trait_ref);
}
}
traits_
}
_ => vec![],
};
for t in traits_from_env.into_iter().flat_map(move |t| all_super_trait_refs(db, t)) {
let data = db.trait_data(t.hir_trait_id());
for (name, assoc_id) in &data.items {
match assoc_id {
AssocItemId::TypeAliasId(alias) => {
if let Some(result) = cb(name, &t, *alias) {
return Some(result);
}
}
AssocItemId::FunctionId(_) | AssocItemId::ConstId(_) => {}
}
}
}
None
}
/// Build the type of all specific fields of a struct or enum variant.
pub(crate) fn field_types_query(
db: &dyn HirDatabase,
variant_id: VariantId,
) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
let var_data = variant_data(db.upcast(), variant_id);
let (resolver, def): (_, GenericDefId) = match variant_id {
VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
};
let generics = generics(db.upcast(), def);
let mut res = ArenaMap::default();
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
for (field_id, field_data) in var_data.fields().iter() {
res.insert(field_id, Binders::new(generics.len(), ctx.lower_ty(&field_data.type_ref)))
}
Arc::new(res)
}
/// This query exists only to be used when resolving short-hand associated types
/// like `T::Item`.
///
/// See the analogous query in rustc and its comment:
/// https://github.com/rust-lang/rust/blob/9150f844e2624eb013ec78ca08c1d416e6644026/src/librustc_typeck/astconv.rs#L46
/// This is a query mostly to handle cycles somewhat gracefully; e.g. the
/// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
/// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
pub(crate) fn generic_predicates_for_param_query(
db: &dyn HirDatabase,
param_id: TypeParamId,
) -> Arc<[Binders<GenericPredicate>]> {
let resolver = param_id.parent.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
let generics = generics(db.upcast(), param_id.parent);
resolver
.where_predicates_in_scope()
// we have to filter out all other predicates *first*, before attempting to lower them
.filter(|pred| match pred {
WherePredicate::ForLifetime { target, .. }
| WherePredicate::TypeBound { target, .. } => match target {
WherePredicateTypeTarget::TypeRef(type_ref) => {
ctx.lower_ty_only_param(type_ref) == Some(param_id)
}
WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id,
},
WherePredicate::Lifetime { .. } => false,
})
.flat_map(|pred| ctx.lower_where_predicate(pred).map(|p| Binders::new(generics.len(), p)))
.collect()
}
pub(crate) fn generic_predicates_for_param_recover(
_db: &dyn HirDatabase,
_cycle: &[String],
_param_id: &TypeParamId,
) -> Arc<[Binders<GenericPredicate>]> {
Arc::new([])
}
pub(crate) fn trait_environment_query(
db: &dyn HirDatabase,
def: GenericDefId,
) -> Arc<TraitEnvironment> {
let resolver = def.resolver(db.upcast());
let ctx = TyLoweringContext::new(db, &resolver)
.with_type_param_mode(TypeParamLoweringMode::Placeholder);
let mut traits_in_scope = Vec::new();
let mut clauses = Vec::new();
for pred in resolver.where_predicates_in_scope() {
for pred in ctx.lower_where_predicate(pred) {
if pred.is_error() {
continue;
}
if let GenericPredicate::Implemented(tr) = &pred {
traits_in_scope.push((tr.self_type_parameter().clone(), tr.hir_trait_id()));
}
let program_clause: chalk_ir::ProgramClause<Interner> =
pred.clone().to_chalk(db).cast(&Interner);
clauses.push(program_clause.into_from_env_clause(&Interner));
}
}
let container: Option<AssocContainerId> = match def {
// FIXME: is there a function for this?
GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
GenericDefId::AdtId(_) => None,
GenericDefId::TraitId(_) => None,
GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
GenericDefId::ImplId(_) => None,
GenericDefId::EnumVariantId(_) => None,
GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
};
if let Some(AssocContainerId::TraitId(trait_id)) = container {
// add `Self: Trait<T1, T2, ...>` to the environment in trait
// function default implementations (and hypothetical code
// inside consts or type aliases)
cov_mark::hit!(trait_self_implements_self);
let substs = Substitution::type_params(db, trait_id);
let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
let pred = GenericPredicate::Implemented(trait_ref);
let program_clause: chalk_ir::ProgramClause<Interner> =
pred.clone().to_chalk(db).cast(&Interner);
clauses.push(program_clause.into_from_env_clause(&Interner));
}
let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses);
Arc::new(TraitEnvironment { traits_from_clauses: traits_in_scope, env })
}
/// Resolve the where clause(s) of an item with generics.
pub(crate) fn generic_predicates_query(
db: &dyn HirDatabase,
def: GenericDefId,
) -> Arc<[Binders<GenericPredicate>]> {
let resolver = def.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
let generics = generics(db.upcast(), def);
resolver
.where_predicates_in_scope()
.flat_map(|pred| ctx.lower_where_predicate(pred).map(|p| Binders::new(generics.len(), p)))
.collect()
}
/// Resolve the default type params from generics
pub(crate) fn generic_defaults_query(
db: &dyn HirDatabase,
def: GenericDefId,
) -> Arc<[Binders<Ty>]> {
let resolver = def.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
let generic_params = generics(db.upcast(), def);
let defaults = generic_params
.iter()
.enumerate()
.map(|(idx, (_, p))| {
let mut ty =
p.default.as_ref().map_or(TyKind::Unknown.intern(&Interner), |t| ctx.lower_ty(t));
// Each default can only refer to previous parameters.
ty.walk_mut_binders(
&mut |ty, binders| match ty.interned_mut() {
TyKind::BoundVar(BoundVar { debruijn, index }) if *debruijn == binders => {
if *index >= idx {
// type variable default referring to parameter coming
// after it. This is forbidden (FIXME: report
// diagnostic)
*ty = TyKind::Unknown.intern(&Interner);
}
}
_ => {}
},
DebruijnIndex::INNERMOST,
);
Binders::new(idx, ty)
})
.collect();
defaults
}
fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
let data = db.function_data(def);
let resolver = def.resolver(db.upcast());
let ctx_params = TyLoweringContext::new(db, &resolver)
.with_impl_trait_mode(ImplTraitLoweringMode::Variable)
.with_type_param_mode(TypeParamLoweringMode::Variable);
let params = data.params.iter().map(|tr| (&ctx_params).lower_ty(tr)).collect::<Vec<_>>();
let ctx_ret = TyLoweringContext::new(db, &resolver)
.with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
.with_type_param_mode(TypeParamLoweringMode::Variable);
let ret = (&ctx_ret).lower_ty(&data.ret_type);
let generics = generics(db.upcast(), def.into());
let num_binders = generics.len();
Binders::new(num_binders, CallableSig::from_params_and_return(params, ret, data.is_varargs))
}
/// Build the declared type of a function. This should not need to look at the
/// function body.
fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
let generics = generics(db.upcast(), def.into());
let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
Binders::new(
substs.len(),
TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
)
}
/// Build the declared type of a const.
fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
let data = db.const_data(def);
let generics = generics(db.upcast(), def.into());
let resolver = def.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
Binders::new(generics.len(), ctx.lower_ty(&data.type_ref))
}
/// Build the declared type of a static.
fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
let data = db.static_data(def);
let resolver = def.resolver(db.upcast());
let ctx = TyLoweringContext::new(db, &resolver);
Binders::new(0, ctx.lower_ty(&data.type_ref))
}
fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
let struct_data = db.struct_data(def);
let fields = struct_data.variant_data.fields();
let resolver = def.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
let ret = type_for_adt(db, def.into());
Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
}
/// Build the type of a tuple struct constructor.
fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
let struct_data = db.struct_data(def);
if let StructKind::Unit = struct_data.variant_data.kind() {
return type_for_adt(db, def.into());
}
let generics = generics(db.upcast(), def.into());
let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
Binders::new(
substs.len(),
TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
)
}
fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
let enum_data = db.enum_data(def.parent);
let var_data = &enum_data.variants[def.local_id];
let fields = var_data.variant_data.fields();
let resolver = def.parent.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
let ret = type_for_adt(db, def.parent.into());
Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
}
/// Build the type of a tuple enum variant constructor.
fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
let enum_data = db.enum_data(def.parent);
let var_data = &enum_data.variants[def.local_id].variant_data;
if let StructKind::Unit = var_data.kind() {
return type_for_adt(db, def.parent.into());
}
let generics = generics(db.upcast(), def.parent.into());
let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
Binders::new(
substs.len(),
TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
)
}
fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
let generics = generics(db.upcast(), adt.into());
let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
Binders::new(substs.len(), Ty::adt_ty(adt, substs))
}
fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
let generics = generics(db.upcast(), t.into());
let resolver = t.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
if db.type_alias_data(t).is_extern {
Binders::new(0, TyKind::ForeignType(crate::to_foreign_def_id(t)).intern(&Interner))
} else {
let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
let type_ref = &db.type_alias_data(t).type_ref;
let inner = ctx.lower_ty(type_ref.as_ref().unwrap_or(&TypeRef::Error));
Binders::new(substs.len(), inner)
}
}
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub enum CallableDefId {
FunctionId(FunctionId),
StructId(StructId),
EnumVariantId(EnumVariantId),
}
impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId);
impl CallableDefId {
pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
let db = db.upcast();
match self {
CallableDefId::FunctionId(f) => f.lookup(db).module(db),
CallableDefId::StructId(s) => s.lookup(db).container,
CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container,
}
.krate()
}
}
impl From<CallableDefId> for GenericDefId {
fn from(def: CallableDefId) -> GenericDefId {
match def {
CallableDefId::FunctionId(f) => f.into(),
CallableDefId::StructId(s) => s.into(),
CallableDefId::EnumVariantId(e) => e.into(),
}
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum TyDefId {
BuiltinType(BuiltinType),
AdtId(AdtId),
TypeAliasId(TypeAliasId),
}
impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId);
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum ValueTyDefId {
FunctionId(FunctionId),
StructId(StructId),
UnionId(UnionId),
EnumVariantId(EnumVariantId),
ConstId(ConstId),
StaticId(StaticId),
}
impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId);
/// Build the declared type of an item. This depends on the namespace; e.g. for
/// `struct Foo(usize)`, we have two types: The type of the struct itself, and
/// the constructor function `(usize) -> Foo` which lives in the values
/// namespace.
pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
match def {
TyDefId::BuiltinType(it) => Binders::new(0, Ty::builtin(it)),
TyDefId::AdtId(it) => type_for_adt(db, it),
TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
}
}
pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
let num_binders = match *def {
TyDefId::BuiltinType(_) => 0,
TyDefId::AdtId(it) => generics(db.upcast(), it.into()).len(),
TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()).len(),
};
Binders::new(num_binders, TyKind::Unknown.intern(&Interner))
}
pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
match def {
ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()),
ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
ValueTyDefId::ConstId(it) => type_for_const(db, it),
ValueTyDefId::StaticId(it) => type_for_static(db, it),
}
}
pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
let impl_data = db.impl_data(impl_id);
let resolver = impl_id.resolver(db.upcast());
let generics = generics(db.upcast(), impl_id.into());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
Binders::new(generics.len(), ctx.lower_ty(&impl_data.target_type))
}
pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
let parent_data = db.generic_params(def.parent);
let data = &parent_data.consts[def.local_id];
let resolver = def.parent.resolver(db.upcast());
let ctx = TyLoweringContext::new(db, &resolver);
ctx.lower_ty(&data.ty)
}
pub(crate) fn impl_self_ty_recover(
db: &dyn HirDatabase,
_cycle: &[String],
impl_id: &ImplId,
) -> Binders<Ty> {
let generics = generics(db.upcast(), (*impl_id).into());
Binders::new(generics.len(), TyKind::Unknown.intern(&Interner))
}
pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
let impl_data = db.impl_data(impl_id);
let resolver = impl_id.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
let self_ty = db.impl_self_ty(impl_id);
let target_trait = impl_data.target_trait.as_ref()?;
Some(Binders::new(self_ty.num_binders, ctx.lower_trait_ref(target_trait, Some(self_ty.value))?))
}
pub(crate) fn return_type_impl_traits(
db: &dyn HirDatabase,
def: hir_def::FunctionId,
) -> Option<Arc<Binders<ReturnTypeImplTraits>>> {
// FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe
let data = db.function_data(def);
let resolver = def.resolver(db.upcast());
let ctx_ret = TyLoweringContext::new(db, &resolver)
.with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
.with_type_param_mode(TypeParamLoweringMode::Variable);
let _ret = (&ctx_ret).lower_ty(&data.ret_type);
let generics = generics(db.upcast(), def.into());
let num_binders = generics.len();
let return_type_impl_traits =
ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
if return_type_impl_traits.impl_traits.is_empty() {
None
} else {
Some(Arc::new(Binders::new(num_binders, return_type_impl_traits)))
}
}
pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mutability {
match m {
hir_def::type_ref::Mutability::Shared => Mutability::Not,
hir_def::type_ref::Mutability::Mut => Mutability::Mut,
}
}