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rust/crates/hir-ty/src/lower.rs

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//! 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 `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, RefMut},
iter,
sync::Arc,
};
use base_db::CrateId;
use chalk_ir::{
cast::Cast, fold::Shift, fold::TypeFoldable, interner::HasInterner, Mutability, Safety,
};
use either::Either;
use hir_def::{
adt::StructKind,
body::{Expander, LowerCtx},
builtin_type::BuiltinType,
generics::{
TypeOrConstParamData, TypeParamProvenance, WherePredicate, WherePredicateTypeTarget,
},
lang_item::{lang_attr, LangItem},
path::{GenericArg, GenericArgs, ModPath, Path, PathKind, PathSegment, PathSegments},
resolver::{HasResolver, Resolver, TypeNs},
type_ref::{ConstRefOrPath, TraitBoundModifier, TraitRef as HirTraitRef, TypeBound, TypeRef},
AdtId, AssocItemId, ConstId, ConstParamId, DefWithBodyId, EnumId, EnumVariantId, FunctionId,
GenericDefId, HasModule, ImplId, ItemContainerId, LocalFieldId, Lookup, ModuleDefId, StaticId,
StructId, TraitId, TypeAliasId, TypeOrConstParamId, TypeParamId, UnionId, VariantId,
};
use hir_expand::{name::Name, ExpandResult};
use intern::Interned;
use la_arena::{Arena, ArenaMap};
use rustc_hash::FxHashSet;
use smallvec::SmallVec;
use stdx::{impl_from, never};
use syntax::ast;
use crate::{
all_super_traits,
consteval::{intern_const_ref, path_to_const, unknown_const, unknown_const_as_generic},
db::HirDatabase,
make_binders,
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},
AliasEq, AliasTy, Binders, BoundVar, CallableSig, Const, DebruijnIndex, DynTy, FnPointer,
FnSig, FnSubst, GenericArgData, ImplTraitId, Interner, ParamKind, PolyFnSig, ProjectionTy,
QuantifiedWhereClause, QuantifiedWhereClauses, ReturnTypeImplTrait, ReturnTypeImplTraits,
Substitution, TraitEnvironment, TraitRef, TraitRefExt, Ty, TyBuilder, TyKind, WhereClause,
};
#[derive(Debug)]
enum ImplTraitLoweringState {
/// 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(RefCell<Arena<ReturnTypeImplTrait>>),
Param(Cell<u16>),
Variable(Cell<u16>),
Disallowed,
}
impl ImplTraitLoweringState {
fn new(impl_trait_mode: ImplTraitLoweringMode) -> ImplTraitLoweringState {
match impl_trait_mode {
ImplTraitLoweringMode::Opaque => Self::Opaque(RefCell::new(Arena::new())),
ImplTraitLoweringMode::Param => Self::Param(Cell::new(0)),
ImplTraitLoweringMode::Variable => Self::Variable(Cell::new(0)),
ImplTraitLoweringMode::Disallowed => Self::Disallowed,
}
}
fn take(&self) -> Self {
match self {
Self::Opaque(x) => Self::Opaque(RefCell::new(x.take())),
Self::Param(x) => Self::Param(Cell::new(x.get())),
Self::Variable(x) => Self::Variable(Cell::new(x.get())),
Self::Disallowed => Self::Disallowed,
}
}
fn swap(&self, impl_trait_mode: &Self) {
match (self, impl_trait_mode) {
(Self::Opaque(x), Self::Opaque(y)) => x.swap(y),
(Self::Param(x), Self::Param(y)) => x.swap(y),
(Self::Variable(x), Self::Variable(y)) => x.swap(y),
(Self::Disallowed, Self::Disallowed) => (),
_ => panic!("mismatched lowering mode"),
}
}
}
#[derive(Debug)]
pub struct TyLoweringContext<'a> {
pub db: &'a dyn HirDatabase,
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: ParamLoweringMode,
impl_trait_mode: ImplTraitLoweringState,
expander: RefCell<Option<Expander>>,
/// Tracks types with explicit `?Sized` bounds.
pub(crate) unsized_types: RefCell<FxHashSet<Ty>>,
}
impl<'a> TyLoweringContext<'a> {
pub fn new(db: &'a dyn HirDatabase, resolver: &'a Resolver) -> Self {
let impl_trait_mode = ImplTraitLoweringState::Disallowed;
let type_param_mode = ParamLoweringMode::Placeholder;
let in_binders = DebruijnIndex::INNERMOST;
Self {
db,
resolver,
in_binders,
impl_trait_mode,
type_param_mode,
expander: RefCell::new(None),
unsized_types: RefCell::default(),
}
}
pub fn with_debruijn<T>(
&self,
debruijn: DebruijnIndex,
f: impl FnOnce(&TyLoweringContext<'_>) -> T,
) -> T {
let impl_trait_mode = self.impl_trait_mode.take();
let expander = self.expander.take();
let unsized_types = self.unsized_types.take();
let new_ctx = Self {
in_binders: debruijn,
impl_trait_mode,
expander: RefCell::new(expander),
unsized_types: RefCell::new(unsized_types),
..*self
};
let result = f(&new_ctx);
self.impl_trait_mode.swap(&new_ctx.impl_trait_mode);
self.expander.replace(new_ctx.expander.into_inner());
self.unsized_types.replace(new_ctx.unsized_types.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: ImplTraitLoweringState::new(impl_trait_mode), ..self }
}
pub fn with_type_param_mode(self, type_param_mode: ParamLoweringMode) -> 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 ParamLoweringMode {
Placeholder,
Variable,
}
impl<'a> TyLoweringContext<'a> {
pub fn lower_ty(&self, type_ref: &TypeRef) -> Ty {
self.lower_ty_ext(type_ref).0
}
fn generics(&self) -> Generics {
generics(
self.db.upcast(),
self.resolver
.generic_def()
.expect("there should be generics if there's a generic param"),
)
}
pub 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, len) => {
let inner_ty = self.lower_ty(inner);
let const_len = const_or_path_to_chalk(
self.db,
self.resolver,
TyBuilder::usize(),
len,
self.type_param_mode,
|| self.generics(),
self.in_binders,
);
TyKind::Array(inner_ty, const_len).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);
let lifetime = static_lifetime();
TyKind::Ref(lower_to_chalk_mutability(*mutability), lifetime, inner_ty)
.intern(Interner)
}
TypeRef::Placeholder => TyKind::Error.intern(Interner),
&TypeRef::Fn(ref params, variadic, is_unsafe) => {
let substs = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
Substitution::from_iter(Interner, params.iter().map(|(_, tr)| ctx.lower_ty(tr)))
});
TyKind::Function(FnPointer {
num_binders: 0, // FIXME lower `for<'a> fn()` correctly
sig: FnSig {
abi: (),
safety: if is_unsafe { Safety::Unsafe } else { Safety::Safe },
variadic,
},
substitution: FnSubst(substs),
})
.intern(Interner)
}
TypeRef::DynTrait(bounds) => self.lower_dyn_trait(bounds),
TypeRef::ImplTrait(bounds) => {
match &self.impl_trait_mode {
ImplTraitLoweringState::Opaque(opaque_type_data) => {
let func = match self.resolver.generic_def() {
Some(GenericDefId::FunctionId(f)) => f,
_ => panic!("opaque impl trait lowering in non-function"),
};
// this dance is to make sure the data is in the right
// place even if we encounter more opaque types while
// lowering the bounds
let idx = opaque_type_data.borrow_mut().alloc(ReturnTypeImplTrait {
bounds: crate::make_single_type_binders(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, func)
});
opaque_type_data.borrow_mut()[idx] = actual_opaque_type_data;
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 = generics.bound_vars_subst(self.db, self.in_binders);
TyKind::OpaqueType(opaque_ty_id, parameters).intern(Interner)
}
ImplTraitLoweringState::Param(counter) => {
let idx = counter.get();
// FIXME we're probably doing something wrong here
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)| {
matches!(
data,
TypeOrConstParamData::TypeParamData(data)
if data.provenance == TypeParamProvenance::ArgumentImplTrait
)
})
.nth(idx as usize)
.map_or(TyKind::Error, |(id, _)| {
TyKind::Placeholder(to_placeholder_idx(self.db, id))
});
param.intern(Interner)
} else {
TyKind::Error.intern(Interner)
}
}
ImplTraitLoweringState::Variable(counter) => {
let idx = counter.get();
// FIXME we're probably doing something wrong here
counter.set(idx + count_impl_traits(type_ref) as u16);
let (
_parent_params,
self_params,
list_params,
const_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, 0)
};
TyKind::BoundVar(BoundVar::new(
self.in_binders,
idx as usize + self_params + list_params + const_params,
))
.intern(Interner)
}
ImplTraitLoweringState::Disallowed => {
// FIXME: report error
TyKind::Error.intern(Interner)
}
}
}
TypeRef::Macro(macro_call) => {
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 = {
let macro_call = macro_call.to_node(self.db.upcast());
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.current_file_id());
let type_ref = TypeRef::from_ast(&ctx, expanded);
drop(expander);
let ty = self.lower_ty(&type_ref);
self.expander
.borrow_mut()
.as_mut()
.unwrap()
.exit(self.db.upcast(), mark);
Some(ty)
}
_ => {
drop(expander);
None
}
}
};
// drop the expander, resetting it to pre-recursion state
if recursion_start {
*self.expander.borrow_mut() = None;
}
ty.unwrap_or_else(|| TyKind::Error.intern(Interner))
}
TypeRef::Error => TyKind::Error.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<TypeOrConstParamId> {
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) {
Some((it, None)) => it,
_ => return None,
};
match resolution {
TypeNs::GenericParam(param_id) => Some(param_id.into()),
_ => 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>) {
match remaining_segments.len() {
0 => (ty, res),
1 => {
// resolve unselected assoc types
let segment = remaining_segments.first().unwrap();
(self.select_associated_type(res, segment), None)
}
_ => {
// FIXME report error (ambiguous associated type)
(TyKind::Error.intern(Interner), None)
}
}
}
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_) => {
let ty = match remaining_segments.len() {
1 => {
let trait_ref =
self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, None);
let segment = remaining_segments.first().unwrap();
let found = self
.db
.trait_data(trait_ref.hir_trait_id())
.associated_type_by_name(segment.name);
match found {
Some(associated_ty) => {
// FIXME: `substs_from_path_segment()` pushes `TyKind::Error` for every parent
// generic params. It's inefficient to splice the `Substitution`s, so we may want
// that method to optionally take parent `Substitution` as we already know them at
// this point (`trait_ref.substitution`).
let substitution = self.substs_from_path_segment(
segment,
Some(associated_ty.into()),
false,
None,
);
let len_self =
generics(self.db.upcast(), associated_ty.into()).len_self();
let substitution = Substitution::from_iter(
Interner,
substitution
.iter(Interner)
.take(len_self)
.chain(trait_ref.substitution.iter(Interner)),
);
TyKind::Alias(AliasTy::Projection(ProjectionTy {
associated_ty_id: to_assoc_type_id(associated_ty),
substitution,
}))
.intern(Interner)
}
None => {
// FIXME: report error (associated type not found)
TyKind::Error.intern(Interner)
}
}
}
0 => {
// 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::Error.intern(Interner)
}
};
return (ty, None);
}
TypeNs::TraitAliasId(_) => {
// FIXME(trait_alias): Implement trait alias.
return (TyKind::Error.intern(Interner), None);
}
TypeNs::GenericParam(param_id) => {
let generics = generics(
self.db.upcast(),
self.resolver.generic_def().expect("generics in scope"),
);
match self.type_param_mode {
ParamLoweringMode::Placeholder => {
TyKind::Placeholder(to_placeholder_idx(self.db, param_id.into()))
}
ParamLoweringMode::Variable => {
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))
}
}
.intern(Interner)
}
TypeNs::SelfType(impl_id) => {
let def =
self.resolver.generic_def().expect("impl should have generic param scope");
let generics = generics(self.db.upcast(), def);
match self.type_param_mode {
ParamLoweringMode::Placeholder => {
// `def` can be either impl itself or item within, and we need impl itself
// now.
let generics = generics.parent_generics().unwrap_or(&generics);
let subst = generics.placeholder_subst(self.db);
self.db.impl_self_ty(impl_id).substitute(Interner, &subst)
}
ParamLoweringMode::Variable => {
let starting_from = match def {
GenericDefId::ImplId(_) => 0,
// `def` is an item within impl. We need to substitute `BoundVar`s but
// remember that they are for parent (i.e. impl) generic params so they
// come after our own params.
_ => generics.len_self(),
};
TyBuilder::impl_self_ty(self.db, impl_id)
.fill_with_bound_vars(self.in_binders, starting_from)
.build()
}
}
}
TypeNs::AdtSelfType(adt) => {
let generics = generics(self.db.upcast(), adt.into());
let substs = match self.type_param_mode {
ParamLoweringMode::Placeholder => generics.placeholder_subst(self.db),
ParamLoweringMode::Variable => {
generics.bound_vars_subst(self.db, self.in_binders)
}
};
self.db.ty(adt.into()).substitute(Interner, &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::Error.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) {
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"),
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 {
let Some((def, res)) = self.resolver.generic_def().zip(res) else {
return TyKind::Error.intern(Interner);
};
let ty = named_associated_type_shorthand_candidates(
self.db,
def,
res,
Some(segment.name.clone()),
move |name, t, associated_ty| {
if name != segment.name {
return None;
}
let parent_subst = t.substitution.clone();
let parent_subst = match self.type_param_mode {
ParamLoweringMode::Placeholder => {
// if we're lowering to placeholders, we have to put them in now.
let generics = generics(self.db.upcast(), def);
let s = generics.placeholder_subst(self.db);
s.apply(parent_subst, Interner)
}
ParamLoweringMode::Variable => {
// We need to shift in the bound vars, since
// `named_associated_type_shorthand_candidates` does not do that.
parent_subst.shifted_in_from(Interner, self.in_binders)
}
};
// FIXME: `substs_from_path_segment()` pushes `TyKind::Error` for every parent
// generic params. It's inefficient to splice the `Substitution`s, so we may want
// that method to optionally take parent `Substitution` as we already know them at
// this point (`t.substitution`).
let substs = self.substs_from_path_segment(
segment.clone(),
Some(associated_ty.into()),
false,
None,
);
let len_self = generics(self.db.upcast(), associated_ty.into()).len_self();
let substs = Substitution::from_iter(
Interner,
substs.iter(Interner).take(len_self).chain(parent_subst.iter(Interner)),
);
Some(
TyKind::Alias(AliasTy::Projection(ProjectionTy {
associated_ty_id: to_assoc_type_id(associated_ty),
substitution: substs,
}))
.intern(Interner),
)
},
);
ty.unwrap_or_else(|| TyKind::Error.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, None);
self.db.ty(typeable).substitute(Interner, &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();
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 = len.checked_sub(2).and_then(|idx| path.segments().get(idx));
let segment = match penultimate {
Some(segment) if segment.args_and_bindings.is_some() => Some(segment),
_ => last,
};
(segment, Some(var.parent.into()))
}
};
if let Some(segment) = segment {
self.substs_from_path_segment(segment, generic_def, infer_args, None)
} else if let Some(generic_def) = generic_def {
// lang item
self.substs_from_args_and_bindings(None, Some(generic_def), infer_args, None)
} else {
Substitution::empty(Interner)
}
}
fn substs_from_path_segment(
&self,
segment: PathSegment<'_>,
def: Option<GenericDefId>,
infer_args: bool,
explicit_self_ty: Option<Ty>,
) -> Substitution {
self.substs_from_args_and_bindings(
segment.args_and_bindings,
def,
infer_args,
explicit_self_ty,
)
}
fn substs_from_args_and_bindings(
&self,
args_and_bindings: Option<&GenericArgs>,
def: Option<GenericDefId>,
infer_args: bool,
explicit_self_ty: Option<Ty>,
) -> Substitution {
// Remember that the item's own generic args come before its parent's.
let mut substs = Vec::new();
let def = if let Some(d) = def {
d
} else {
return Substitution::empty(Interner);
};
let def_generics = generics(self.db.upcast(), def);
let (parent_params, self_params, type_params, const_params, impl_trait_params) =
def_generics.provenance_split();
let item_len = self_params + type_params + const_params + impl_trait_params;
let total_len = parent_params + item_len;
let ty_error = TyKind::Error.intern(Interner).cast(Interner);
let mut def_generic_iter = def_generics.iter_id();
let fill_self_params = || {
for x in explicit_self_ty
.into_iter()
.map(|x| x.cast(Interner))
.chain(iter::repeat(ty_error.clone()))
.take(self_params)
{
if let Some(id) = def_generic_iter.next() {
assert!(id.is_left());
substs.push(x);
}
}
};
let mut had_explicit_args = false;
if let Some(generic_args) = &args_and_bindings {
if !generic_args.has_self_type {
fill_self_params();
}
let expected_num = if generic_args.has_self_type {
self_params + type_params + const_params
} else {
type_params + const_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::Lifetime(_)))
.skip(skip)
.take(expected_num)
{
if let Some(id) = def_generic_iter.next() {
if let Some(x) = generic_arg_to_chalk(
self.db,
id,
arg,
&mut (),
|_, type_ref| self.lower_ty(type_ref),
|_, c, ty| {
const_or_path_to_chalk(
self.db,
self.resolver,
ty,
c,
self.type_param_mode,
|| self.generics(),
self.in_binders,
)
},
) {
had_explicit_args = true;
substs.push(x);
} else {
// we just filtered them out
never!("Unexpected lifetime argument");
}
}
}
} else {
fill_self_params();
}
// These params include those of parent.
let remaining_params: SmallVec<[_; 2]> = def_generic_iter
.map(|eid| match eid {
Either::Left(_) => ty_error.clone(),
Either::Right(x) => unknown_const_as_generic(self.db.const_param_ty(x)),
})
.collect();
assert_eq!(remaining_params.len() + substs.len(), total_len);
// handle defaults. In expression or pattern path segments without
// explicitly specified type arguments, missing type arguments are inferred
// (i.e. defaults aren't used).
// Generic parameters for associated types are not supposed to have defaults, so we just
// ignore them.
let is_assoc_ty = if let GenericDefId::TypeAliasId(id) = def {
let container = id.lookup(self.db.upcast()).container;
matches!(container, ItemContainerId::TraitId(_))
} else {
false
};
if !is_assoc_ty && (!infer_args || had_explicit_args) {
let defaults = self.db.generic_defaults(def);
assert_eq!(total_len, defaults.len());
let parent_from = item_len - substs.len();
for (idx, default_ty) in defaults[substs.len()..item_len].iter().enumerate() {
// each default can depend on the previous parameters
let substs_so_far = Substitution::from_iter(
Interner,
substs.iter().cloned().chain(remaining_params[idx..].iter().cloned()),
);
substs.push(default_ty.clone().substitute(Interner, &substs_so_far));
}
// Keep parent's params as unknown.
let mut remaining_params = remaining_params;
substs.extend(remaining_params.drain(parent_from..));
} else {
substs.extend(remaining_params);
}
assert_eq!(substs.len(), total_len);
Substitution::from_iter(Interner, substs)
}
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)? {
// FIXME(trait_alias): We need to handle trait alias here.
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 substs = self.trait_ref_substs_from_path(segment, resolved, explicit_self_ty);
TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs }
}
fn lower_trait_ref(
&self,
trait_ref: &HirTraitRef,
explicit_self_ty: Option<Ty>,
) -> Option<TraitRef> {
self.lower_trait_ref_from_path(&trait_ref.path, explicit_self_ty)
}
fn trait_ref_substs_from_path(
&self,
segment: PathSegment<'_>,
resolved: TraitId,
explicit_self_ty: Option<Ty>,
) -> Substitution {
self.substs_from_path_segment(segment, Some(resolved.into()), false, explicit_self_ty)
}
pub(crate) fn lower_where_predicate(
&'a self,
where_predicate: &'a WherePredicate,
ignore_bindings: bool,
) -> impl Iterator<Item = QuantifiedWhereClause> + '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::TypeOrConstParam(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::TypeOrConstParamId {
parent: generic_def,
local_id: *param_id,
};
let placeholder = to_placeholder_idx(self.db, param_id);
match self.type_param_mode {
ParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
ParamLoweringMode::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, ignore_bindings)
.collect::<Vec<_>>()
.into_iter()
}
WherePredicate::Lifetime { .. } => vec![].into_iter(),
}
}
pub(crate) fn lower_type_bound(
&'a self,
bound: &'a TypeBound,
self_ty: Ty,
ignore_bindings: bool,
) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
let mut bindings = None;
let trait_ref = match bound {
TypeBound::Path(path, TraitBoundModifier::None) => {
bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
bindings
.clone()
.filter(|tr| {
// ignore `T: Drop` or `T: Destruct` bounds.
// - `T: ~const Drop` has a special meaning in Rust 1.61 that we don't implement.
// (So ideally, we'd only ignore `~const Drop` here)
// - `Destruct` impls are built-in in 1.62 (current nightlies as of 08-04-2022), so until
// the builtin impls are supported by Chalk, we ignore them here.
if let Some(lang) = lang_attr(self.db.upcast(), tr.hir_trait_id()) {
if matches!(lang, LangItem::Drop | LangItem::Destruct) {
return false;
}
}
true
})
.map(WhereClause::Implemented)
.map(crate::wrap_empty_binders)
}
TypeBound::Path(path, TraitBoundModifier::Maybe) => {
let sized_trait = self
.db
.lang_item(self.resolver.krate(), LangItem::Sized)
.and_then(|lang_item| lang_item.as_trait());
// Don't lower associated type bindings as the only possible relaxed trait bound
// `?Sized` has no of them.
// If we got another trait here ignore the bound completely.
let trait_id = self
.lower_trait_ref_from_path(path, Some(self_ty.clone()))
.map(|trait_ref| trait_ref.hir_trait_id());
if trait_id == sized_trait {
self.unsized_types.borrow_mut().insert(self_ty);
}
None
}
TypeBound::ForLifetime(_, path) => {
// FIXME Don't silently drop the hrtb lifetimes here
bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
bindings.clone().map(WhereClause::Implemented).map(crate::wrap_empty_binders)
}
TypeBound::Lifetime(_) => None,
TypeBound::Error => None,
};
trait_ref.into_iter().chain(
bindings
.into_iter()
.filter(move |_| !ignore_bindings)
.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 = QuantifiedWhereClause> + 'a {
let last_segment = match bound {
TypeBound::Path(path, TraitBoundModifier::None) | TypeBound::ForLifetime(_, path) => {
path.segments().last()
}
TypeBound::Path(_, TraitBoundModifier::Maybe)
| TypeBound::Error
| TypeBound::Lifetime(_) => None,
};
last_segment
.into_iter()
.filter_map(|segment| segment.args_and_bindings)
.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::new(),
Some(t) => t,
};
// FIXME: `substs_from_path_segment()` pushes `TyKind::Error` for every parent
// generic params. It's inefficient to splice the `Substitution`s, so we may want
// that method to optionally take parent `Substitution` as we already know them at
// this point (`super_trait_ref.substitution`).
let substitution = self.substs_from_path_segment(
// FIXME: This is hack. We shouldn't really build `PathSegment` directly.
PathSegment { name: &binding.name, args_and_bindings: binding.args.as_deref() },
Some(associated_ty.into()),
false, // this is not relevant
Some(super_trait_ref.self_type_parameter(Interner)),
);
let self_params = generics(self.db.upcast(), associated_ty.into()).len_self();
let substitution = Substitution::from_iter(
Interner,
substitution
.iter(Interner)
.take(self_params)
.chain(super_trait_ref.substitution.iter(Interner)),
);
let projection_ty = ProjectionTy {
associated_ty_id: to_assoc_type_id(associated_ty),
substitution,
};
let mut preds: SmallVec<[_; 1]> = 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(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq)));
}
for bound in binding.bounds.iter() {
preds.extend(self.lower_type_bound(
bound,
TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(Interner),
false,
));
}
preds
})
}
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, if present, 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.
// INVARIANT: If this function returns `DynTy`, there should be at least one trait bound.
// These invariants are utilized 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;
}
if bounds.first().and_then(|b| b.trait_id()).is_none() {
// When there's no trait bound, that's an error. This happens when the trait refs
// are unresolved.
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, associated type rebound, or no resolved trait)
TyKind::Error.intern(Interner)
}
}
fn lower_impl_trait(
&self,
bounds: &[Interned<TypeBound>],
func: FunctionId,
) -> 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| {
let mut predicates: Vec<_> = bounds
.iter()
.flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false))
.collect();
if !ctx.unsized_types.borrow().contains(&self_ty) {
let krate = func.lookup(ctx.db.upcast()).module(ctx.db.upcast()).krate();
let sized_trait = ctx
.db
.lang_item(krate, LangItem::Sized)
.and_then(|lang_item| lang_item.as_trait().map(to_chalk_trait_id));
let sized_clause = sized_trait.map(|trait_id| {
let clause = WhereClause::Implemented(TraitRef {
trait_id,
substitution: Substitution::from1(Interner, self_ty.clone()),
});
crate::wrap_empty_binders(clause)
});
predicates.extend(sized_clause.into_iter());
predicates.shrink_to_fit();
}
predicates
});
ReturnTypeImplTrait { bounds: crate::make_single_type_binders(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(crate) 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,
def: GenericDefId,
res: TypeNs,
mut cb: impl FnMut(&Name, TypeAliasId) -> Option<R>,
) -> Option<R> {
named_associated_type_shorthand_candidates(db, def, res, None, |name, _, id| cb(name, id))
}
fn named_associated_type_shorthand_candidates<R>(
db: &dyn HirDatabase,
// If the type parameter is defined in an impl and we're in a method, there
// might be additional where clauses to consider
def: GenericDefId,
res: TypeNs,
assoc_name: Option<Name>,
// Do NOT let `cb` touch `TraitRef` outside of `TyLoweringContext`. Its substitution contains
// free `BoundVar`s that need to be shifted and only `TyLoweringContext` knows how to do that
// properly (see `TyLoweringContext::select_associated_type()`).
mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
) -> Option<R> {
let mut search = |t| {
all_super_trait_refs(db, t, |t| {
let data = db.trait_data(t.hir_trait_id());
for (name, assoc_id) in &data.items {
if let AssocItemId::TypeAliasId(alias) = assoc_id {
if let Some(result) = cb(name, &t, *alias) {
return Some(result);
}
}
}
None
})
};
match res {
TypeNs::SelfType(impl_id) => {
// we're _in_ the impl -- the binders get added back later. Correct,
// but it would be nice to make this more explicit
let trait_ref = db.impl_trait(impl_id)?.into_value_and_skipped_binders().0;
let impl_id_as_generic_def: GenericDefId = impl_id.into();
if impl_id_as_generic_def != def {
// `trait_ref` contains `BoundVar`s bound by impl's `Binders`, but here we need
// `BoundVar`s from `def`'s point of view.
// FIXME: A `HirDatabase` query may be handy if this process is needed in more
// places. It'd be almost identical as `impl_trait_query` where `resolver` would be
// of `def` instead of `impl_id`.
let starting_idx = generics(db.upcast(), def).len_self();
let subst = TyBuilder::subst_for_def(db, impl_id, None)
.fill_with_bound_vars(DebruijnIndex::INNERMOST, starting_idx)
.build();
let trait_ref = subst.apply(trait_ref, Interner);
search(trait_ref)
} else {
search(trait_ref)
}
}
TypeNs::GenericParam(param_id) => {
let predicates = db.generic_predicates_for_param(def, param_id.into(), assoc_name);
let res = predicates.iter().find_map(|pred| match pred.skip_binders().skip_binders() {
// FIXME: how to correctly handle higher-ranked bounds here?
WhereClause::Implemented(tr) => search(
tr.clone()
.shifted_out_to(Interner, DebruijnIndex::ONE)
.expect("FIXME unexpected higher-ranked trait bound"),
),
_ => None,
});
if let Some(_) = res {
return res;
}
// Handle `Self::Type` referring to own associated type in trait definitions
if let GenericDefId::TraitId(trait_id) = param_id.parent() {
let trait_generics = generics(db.upcast(), trait_id.into());
if trait_generics.params.type_or_consts[param_id.local_id()].is_trait_self() {
let def_generics = generics(db.upcast(), def);
let starting_idx = match def {
GenericDefId::TraitId(_) => 0,
// `def` is an item within trait. We need to substitute `BoundVar`s but
// remember that they are for parent (i.e. trait) generic params so they
// come after our own params.
_ => def_generics.len_self(),
};
let trait_ref = TyBuilder::trait_ref(db, trait_id)
.fill_with_bound_vars(DebruijnIndex::INNERMOST, starting_idx)
.build();
return search(trait_ref);
}
}
None
}
_ => 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_id.variant_data(db.upcast());
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(ParamLoweringMode::Variable);
for (field_id, field_data) in var_data.fields().iter() {
res.insert(field_id, make_binders(db, &generics, 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,
def: GenericDefId,
param_id: TypeOrConstParamId,
assoc_name: Option<Name>,
) -> Arc<[Binders<QuantifiedWhereClause>]> {
let resolver = def.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(ParamLoweringMode::Variable);
let generics = generics(db.upcast(), def);
let mut predicates: Vec<_> = 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, bound, .. }
| WherePredicate::TypeBound { target, bound, .. } => {
match target {
WherePredicateTypeTarget::TypeRef(type_ref) => {
if ctx.lower_ty_only_param(type_ref) != Some(param_id) {
return false;
}
}
&WherePredicateTypeTarget::TypeOrConstParam(local_id) => {
let target_id = TypeOrConstParamId { parent: def, local_id };
if target_id != param_id {
return false;
}
}
};
match &**bound {
TypeBound::ForLifetime(_, path) | TypeBound::Path(path, _) => {
// Only lower the bound if the trait could possibly define the associated
// type we're looking for.
let assoc_name = match &assoc_name {
Some(it) => it,
None => return true,
};
let tr = match resolver.resolve_path_in_type_ns_fully(db.upcast(), path) {
Some(TypeNs::TraitId(tr)) => tr,
_ => return false,
};
all_super_traits(db.upcast(), tr).iter().any(|tr| {
db.trait_data(*tr).items.iter().any(|(name, item)| {
matches!(item, AssocItemId::TypeAliasId(_)) && name == assoc_name
})
})
}
TypeBound::Lifetime(_) | TypeBound::Error => false,
}
}
WherePredicate::Lifetime { .. } => false,
})
.flat_map(|pred| {
ctx.lower_where_predicate(pred, true).map(|p| make_binders(db, &generics, p))
})
.collect();
let subst = generics.bound_vars_subst(db, DebruijnIndex::INNERMOST);
let explicitly_unsized_tys = ctx.unsized_types.into_inner();
let implicitly_sized_predicates =
implicitly_sized_clauses(db, param_id.parent, &explicitly_unsized_tys, &subst, &resolver)
.map(|p| make_binders(db, &generics, crate::wrap_empty_binders(p)));
predicates.extend(implicitly_sized_predicates);
predicates.into()
}
pub(crate) fn generic_predicates_for_param_recover(
_db: &dyn HirDatabase,
_cycle: &[String],
_def: &GenericDefId,
_param_id: &TypeOrConstParamId,
_assoc_name: &Option<Name>,
) -> Arc<[Binders<QuantifiedWhereClause>]> {
Arc::new([])
}
pub(crate) fn trait_environment_for_body_query(
db: &dyn HirDatabase,
def: DefWithBodyId,
) -> Arc<TraitEnvironment> {
let Some(def) = def.as_generic_def_id() else {
let krate = def.module(db.upcast()).krate();
return Arc::new(TraitEnvironment::empty(krate));
};
db.trait_environment(def)
}
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(ParamLoweringMode::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, false) {
if let WhereClause::Implemented(tr) = &pred.skip_binders() {
traits_in_scope.push((tr.self_type_parameter(Interner).clone(), tr.hir_trait_id()));
}
let program_clause: chalk_ir::ProgramClause<Interner> = pred.cast(Interner);
clauses.push(program_clause.into_from_env_clause(Interner));
}
}
let container: Option<ItemContainerId> = 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::TraitAliasId(_) => 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(ItemContainerId::TraitId(trait_id)) = container {
// add `Self: Trait<T1, T2, ...>` to the environment in trait
// function default implementations (and speculative code
// inside consts or type aliases)
cov_mark::hit!(trait_self_implements_self);
let substs = TyBuilder::placeholder_subst(db, trait_id);
let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
let pred = WhereClause::Implemented(trait_ref);
let program_clause: chalk_ir::ProgramClause<Interner> = pred.cast(Interner);
clauses.push(program_clause.into_from_env_clause(Interner));
}
let subst = generics(db.upcast(), def).placeholder_subst(db);
let explicitly_unsized_tys = ctx.unsized_types.into_inner();
let implicitly_sized_clauses =
implicitly_sized_clauses(db, def, &explicitly_unsized_tys, &subst, &resolver).map(|pred| {
let program_clause: chalk_ir::ProgramClause<Interner> = pred.cast(Interner);
program_clause.into_from_env_clause(Interner)
});
clauses.extend(implicitly_sized_clauses);
let krate = def.module(db.upcast()).krate();
let env = chalk_ir::Environment::new(Interner).add_clauses(Interner, clauses);
Arc::new(TraitEnvironment { krate, block: None, 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<QuantifiedWhereClause>]> {
let resolver = def.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(ParamLoweringMode::Variable);
let generics = generics(db.upcast(), def);
let mut predicates = resolver
.where_predicates_in_scope()
.flat_map(|pred| {
ctx.lower_where_predicate(pred, false).map(|p| make_binders(db, &generics, p))
})
.collect::<Vec<_>>();
let subst = generics.bound_vars_subst(db, DebruijnIndex::INNERMOST);
let explicitly_unsized_tys = ctx.unsized_types.into_inner();
let implicitly_sized_predicates =
implicitly_sized_clauses(db, def, &explicitly_unsized_tys, &subst, &resolver)
.map(|p| make_binders(db, &generics, crate::wrap_empty_binders(p)));
predicates.extend(implicitly_sized_predicates);
predicates.into()
}
/// Generate implicit `: Sized` predicates for all generics that has no `?Sized` bound.
/// Exception is Self of a trait def.
fn implicitly_sized_clauses<'a>(
db: &dyn HirDatabase,
def: GenericDefId,
explicitly_unsized_tys: &'a FxHashSet<Ty>,
substitution: &'a Substitution,
resolver: &Resolver,
) -> impl Iterator<Item = WhereClause> + 'a {
let is_trait_def = matches!(def, GenericDefId::TraitId(..));
let generic_args = &substitution.as_slice(Interner)[is_trait_def as usize..];
let sized_trait = db
.lang_item(resolver.krate(), LangItem::Sized)
.and_then(|lang_item| lang_item.as_trait().map(to_chalk_trait_id));
sized_trait.into_iter().flat_map(move |sized_trait| {
let implicitly_sized_tys = generic_args
.iter()
.filter_map(|generic_arg| generic_arg.ty(Interner))
.filter(move |&self_ty| !explicitly_unsized_tys.contains(self_ty));
implicitly_sized_tys.map(move |self_ty| {
WhereClause::Implemented(TraitRef {
trait_id: sized_trait,
substitution: Substitution::from1(Interner, self_ty.clone()),
})
})
})
}
/// Resolve the default type params from generics
pub(crate) fn generic_defaults_query(
db: &dyn HirDatabase,
def: GenericDefId,
) -> Arc<[Binders<chalk_ir::GenericArg<Interner>>]> {
let resolver = def.resolver(db.upcast());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(ParamLoweringMode::Variable);
let generic_params = generics(db.upcast(), def);
let parent_start_idx = generic_params.len_self();
let defaults = generic_params
.iter()
.enumerate()
.map(|(idx, (id, p))| {
let p = match p {
TypeOrConstParamData::TypeParamData(p) => p,
TypeOrConstParamData::ConstParamData(_) => {
// FIXME: implement const generic defaults
let val = unknown_const_as_generic(
db.const_param_ty(ConstParamId::from_unchecked(id)),
);
return make_binders(db, &generic_params, val);
}
};
let mut ty =
p.default.as_ref().map_or(TyKind::Error.intern(Interner), |t| ctx.lower_ty(t));
// Each default can only refer to previous parameters.
// Type variable default referring to parameter coming
// after it is forbidden (FIXME: report diagnostic)
ty = fallback_bound_vars(ty, idx, parent_start_idx);
crate::make_binders(db, &generic_params, ty.cast(Interner))
})
.collect();
defaults
}
pub(crate) fn generic_defaults_recover(
db: &dyn HirDatabase,
_cycle: &[String],
def: &GenericDefId,
) -> Arc<[Binders<crate::GenericArg>]> {
let generic_params = generics(db.upcast(), *def);
// FIXME: this code is not covered in tests.
// we still need one default per parameter
let defaults = generic_params
.iter_id()
.map(|id| {
let val = match id {
Either::Left(_) => {
GenericArgData::Ty(TyKind::Error.intern(Interner)).intern(Interner)
}
Either::Right(id) => unknown_const_as_generic(db.const_param_ty(id)),
};
crate::make_binders(db, &generic_params, val)
})
.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(ParamLoweringMode::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(ParamLoweringMode::Variable);
let ret = ctx_ret.lower_ty(&data.ret_type);
let generics = generics(db.upcast(), def.into());
let sig = CallableSig::from_params_and_return(
params,
ret,
data.is_varargs(),
if data.has_unsafe_kw() { Safety::Unsafe } else { Safety::Safe },
);
make_binders(db, &generics, sig)
}
/// 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 = generics.bound_vars_subst(db, DebruijnIndex::INNERMOST);
make_binders(
db,
&generics,
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(ParamLoweringMode::Variable);
make_binders(db, &generics, 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::empty(Interner, 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(ParamLoweringMode::Variable);
let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
let (ret, binders) = type_for_adt(db, def.into()).into_value_and_skipped_binders();
Binders::new(binders, CallableSig::from_params_and_return(params, ret, false, Safety::Safe))
}
/// 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 = generics.bound_vars_subst(db, DebruijnIndex::INNERMOST);
make_binders(
db,
&generics,
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(ParamLoweringMode::Variable);
let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
let (ret, binders) = type_for_adt(db, def.parent.into()).into_value_and_skipped_binders();
Binders::new(binders, CallableSig::from_params_and_return(params, ret, false, Safety::Safe))
}
/// 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 = generics.bound_vars_subst(db, DebruijnIndex::INNERMOST);
make_binders(
db,
&generics,
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 subst = generics.bound_vars_subst(db, DebruijnIndex::INNERMOST);
let ty = TyKind::Adt(crate::AdtId(adt), subst).intern(Interner);
make_binders(db, &generics, ty)
}
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(ParamLoweringMode::Variable);
if db.type_alias_data(t).is_extern {
Binders::empty(Interner, TyKind::Foreign(crate::to_foreign_def_id(t)).intern(Interner))
} else {
let type_ref = &db.type_alias_data(t).type_ref;
let inner = ctx.lower_ty(type_ref.as_deref().unwrap_or(&TypeRef::Error));
make_binders(db, &generics, 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 From<CallableDefId> for ModuleDefId {
fn from(def: CallableDefId) -> ModuleDefId {
match def {
CallableDefId::FunctionId(f) => ModuleDefId::FunctionId(f),
CallableDefId::StructId(s) => ModuleDefId::AdtId(AdtId::StructId(s)),
CallableDefId::EnumVariantId(e) => ModuleDefId::EnumVariantId(e),
}
}
}
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);
impl ValueTyDefId {
pub(crate) fn to_generic_def_id(self) -> Option<GenericDefId> {
match self {
Self::FunctionId(id) => Some(id.into()),
Self::StructId(id) => Some(id.into()),
Self::UnionId(id) => Some(id.into()),
Self::EnumVariantId(var) => Some(var.into()),
Self::ConstId(id) => Some(id.into()),
Self::StaticId(_) => None,
}
}
}
/// 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::empty(Interner, TyBuilder::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 generics = match *def {
TyDefId::BuiltinType(_) => return Binders::empty(Interner, TyKind::Error.intern(Interner)),
TyDefId::AdtId(it) => generics(db.upcast(), it.into()),
TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()),
};
make_binders(db, &generics, TyKind::Error.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_loc = impl_id.lookup(db.upcast());
let impl_data = db.impl_data(impl_id);
let resolver = impl_id.resolver(db.upcast());
let _cx = stdx::panic_context::enter(format!(
"impl_self_ty_query({impl_id:?} -> {impl_loc:?} -> {impl_data:?})"
));
let generics = generics(db.upcast(), impl_id.into());
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(ParamLoweringMode::Variable);
make_binders(db, &generics, ctx.lower_ty(&impl_data.self_ty))
}
// returns None if def is a type arg
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.type_or_consts[def.local_id()];
let resolver = def.parent().resolver(db.upcast());
let ctx = TyLoweringContext::new(db, &resolver);
match data {
TypeOrConstParamData::TypeParamData(_) => {
never!();
Ty::new(Interner, TyKind::Error)
}
TypeOrConstParamData::ConstParamData(d) => ctx.lower_ty(&d.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());
make_binders(db, &generics, TyKind::Error.intern(Interner))
}
pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
let impl_loc = impl_id.lookup(db.upcast());
let impl_data = db.impl_data(impl_id);
let resolver = impl_id.resolver(db.upcast());
let _cx = stdx::panic_context::enter(format!(
"impl_trait_query({impl_id:?} -> {impl_loc:?} -> {impl_data:?})"
));
let ctx =
TyLoweringContext::new(db, &resolver).with_type_param_mode(ParamLoweringMode::Variable);
let (self_ty, binders) = db.impl_self_ty(impl_id).into_value_and_skipped_binders();
let target_trait = impl_data.target_trait.as_ref()?;
Some(Binders::new(binders, ctx.lower_trait_ref(target_trait, Some(self_ty))?))
}
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(ParamLoweringMode::Variable);
let _ret = ctx_ret.lower_ty(&data.ret_type);
let generics = generics(db.upcast(), def.into());
let return_type_impl_traits = ReturnTypeImplTraits {
impl_traits: match ctx_ret.impl_trait_mode {
ImplTraitLoweringState::Opaque(x) => x.into_inner(),
_ => unreachable!(),
},
};
if return_type_impl_traits.impl_traits.is_empty() {
None
} else {
Some(Arc::new(make_binders(db, &generics, 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,
}
}
/// Checks if the provided generic arg matches its expected kind, then lower them via
/// provided closures. Use unknown if there was kind mismatch.
///
/// Returns `Some` of the lowered generic arg. `None` if the provided arg is a lifetime.
pub(crate) fn generic_arg_to_chalk<'a, T>(
db: &dyn HirDatabase,
kind_id: Either<TypeParamId, ConstParamId>,
arg: &'a GenericArg,
this: &mut T,
for_type: impl FnOnce(&mut T, &TypeRef) -> Ty + 'a,
for_const: impl FnOnce(&mut T, &ConstRefOrPath, Ty) -> Const + 'a,
) -> Option<crate::GenericArg> {
let kind = match kind_id {
Either::Left(_) => ParamKind::Type,
Either::Right(id) => {
let ty = db.const_param_ty(id);
ParamKind::Const(ty)
}
};
Some(match (arg, kind) {
(GenericArg::Type(type_ref), ParamKind::Type) => {
let ty = for_type(this, type_ref);
GenericArgData::Ty(ty).intern(Interner)
}
(GenericArg::Const(c), ParamKind::Const(c_ty)) => {
GenericArgData::Const(for_const(this, c, c_ty)).intern(Interner)
}
(GenericArg::Const(_), ParamKind::Type) => {
GenericArgData::Ty(TyKind::Error.intern(Interner)).intern(Interner)
}
(GenericArg::Type(t), ParamKind::Const(c_ty)) => {
// We want to recover simple idents, which parser detects them
// as types. Maybe here is not the best place to do it, but
// it works.
if let TypeRef::Path(p) = t {
let p = p.mod_path()?;
if p.kind == PathKind::Plain {
if let [n] = p.segments() {
let c = ConstRefOrPath::Path(n.clone());
return Some(
GenericArgData::Const(for_const(this, &c, c_ty)).intern(Interner),
);
}
}
}
unknown_const_as_generic(c_ty)
}
(GenericArg::Lifetime(_), _) => return None,
})
}
pub(crate) fn const_or_path_to_chalk(
db: &dyn HirDatabase,
resolver: &Resolver,
expected_ty: Ty,
value: &ConstRefOrPath,
mode: ParamLoweringMode,
args: impl FnOnce() -> Generics,
debruijn: DebruijnIndex,
) -> Const {
match value {
ConstRefOrPath::Scalar(s) => intern_const_ref(db, s, expected_ty, resolver.krate()),
ConstRefOrPath::Path(n) => {
let path = ModPath::from_segments(PathKind::Plain, Some(n.clone()));
path_to_const(
db,
resolver,
&Path::from_known_path_with_no_generic(path),
mode,
args,
debruijn,
)
.unwrap_or_else(|| unknown_const(expected_ty))
}
}
}
/// Replaces any 'free' `BoundVar`s in `s` by `TyKind::Error` from the perspective of generic
/// parameter whose index is `param_index`. A `BoundVar` is free when it is or (syntactically)
/// appears after the generic parameter of `param_index`.
fn fallback_bound_vars<T: TypeFoldable<Interner> + HasInterner<Interner = Interner>>(
s: T,
param_index: usize,
parent_start: usize,
) -> T {
// Keep in mind that parent generic parameters, if any, come *after* those of the item in
// question. In the diagrams below, `c*` and `p*` represent generic parameters of the item and
// its parent respectively.
let is_allowed = |index| {
if param_index < parent_start {
// The parameter of `param_index` is one from the item in question. Any parent generic
// parameters or the item's generic parameters that come before `param_index` is
// allowed.
// [c1, .., cj, .., ck, p1, .., pl] where cj is `param_index`
// ^^^^^^ ^^^^^^^^^^ these are allowed
!(param_index..parent_start).contains(&index)
} else {
// The parameter of `param_index` is one from the parent generics. Only parent generic
// parameters that come before `param_index` are allowed.
// [c1, .., ck, p1, .., pj, .., pl] where pj is `param_index`
// ^^^^^^ these are allowed
(parent_start..param_index).contains(&index)
}
};
crate::fold_free_vars(
s,
|bound, binders| {
if bound.index_if_innermost().map_or(true, is_allowed) {
bound.shifted_in_from(binders).to_ty(Interner)
} else {
TyKind::Error.intern(Interner)
}
},
|ty, bound, binders| {
if bound.index_if_innermost().map_or(true, is_allowed) {
bound.shifted_in_from(binders).to_const(Interner, ty)
} else {
unknown_const(ty)
}
},
)
}
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