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rust/compiler/rustc_ast_lowering/src/item.rs
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aerooneqq 2e6a082513 Use per-parent disambiguators
2026-04-21 18:23:40 +03:00

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use std::mem;
use std::sync::Arc;
use rustc_abi::ExternAbi;
use rustc_ast::visit::AssocCtxt;
use rustc_ast::*;
use rustc_data_structures::fx::FxIndexMap;
use rustc_data_structures::steal::Steal;
use rustc_errors::{E0570, ErrorGuaranteed, struct_span_code_err};
use rustc_hir::attrs::{AttributeKind, EiiImplResolution};
use rustc_hir::def::{DefKind, PerNS, Res};
use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId, LocalDefIdMap};
use rustc_hir::definitions::PerParentDisambiguatorState;
use rustc_hir::{
self as hir, HirId, ImplItemImplKind, LifetimeSource, PredicateOrigin, Target, find_attr,
};
use rustc_index::{IndexSlice, IndexVec};
use rustc_middle::span_bug;
use rustc_middle::ty::TyCtxt;
use rustc_span::def_id::DefId;
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::{DUMMY_SP, DesugaringKind, Ident, Span, Symbol, kw, sym};
use smallvec::{SmallVec, smallvec};
use thin_vec::ThinVec;
use tracing::instrument;
use super::errors::{InvalidAbi, InvalidAbiSuggestion, TupleStructWithDefault, UnionWithDefault};
use super::stability::{enabled_names, gate_unstable_abi};
use super::{
AstOwner, FnDeclKind, GenericArgsMode, ImplTraitContext, ImplTraitPosition, LoweringContext,
ParamMode, RelaxedBoundForbiddenReason, RelaxedBoundPolicy, ResolverAstLoweringExt,
};
/// Wraps either IndexVec (during `hir_crate`), which acts like a primary
/// storage for most of the MaybeOwners, or FxIndexMap during delayed AST -> HIR
/// lowering of delegations (`lower_delayed_owner`),
/// in this case we can not modify already created IndexVec, so we use other map.
pub(super) enum Owners<'a, 'hir> {
IndexVec(&'a mut IndexVec<LocalDefId, hir::MaybeOwner<'hir>>),
Map(&'a mut FxIndexMap<LocalDefId, hir::MaybeOwner<'hir>>),
}
impl<'hir> Owners<'_, 'hir> {
fn get_or_insert_mut(&mut self, def_id: LocalDefId) -> &mut hir::MaybeOwner<'hir> {
match self {
Owners::IndexVec(index_vec) => {
index_vec.ensure_contains_elem(def_id, || hir::MaybeOwner::Phantom)
}
Owners::Map(map) => map.entry(def_id).or_insert(hir::MaybeOwner::Phantom),
}
}
}
/// Default disambiguators are used during default lowering, when we lower
/// AST owners in a loop we can use the whole map, in contrast delayed lowering
/// lowers each AST owner separately, so we use readonly disambiguators map
/// with `Steal`s to get disambiguators.
pub(super) enum Disambiguators {
Default(LocalDefIdMap<PerParentDisambiguatorState>),
Delayed(Arc<LocalDefIdMap<Steal<PerParentDisambiguatorState>>>),
}
pub(super) struct ItemLowerer<'a, 'hir, R> {
pub(super) tcx: TyCtxt<'hir>,
pub(super) resolver: &'a mut R,
pub(super) ast_index: &'a IndexSlice<LocalDefId, AstOwner<'a>>,
pub(super) owners: Owners<'a, 'hir>,
pub(super) disambiguators: &'a mut Disambiguators,
}
/// When we have a ty alias we *may* have two where clauses. To give the best diagnostics, we set the span
/// to the where clause that is preferred, if it exists. Otherwise, it sets the span to the other where
/// clause if it exists.
fn add_ty_alias_where_clause(
generics: &mut ast::Generics,
after_where_clause: &ast::WhereClause,
prefer_first: bool,
) {
generics.where_clause.predicates.extend_from_slice(&after_where_clause.predicates);
let mut before = (generics.where_clause.has_where_token, generics.where_clause.span);
let mut after = (after_where_clause.has_where_token, after_where_clause.span);
if !prefer_first {
(before, after) = (after, before);
}
(generics.where_clause.has_where_token, generics.where_clause.span) =
if before.0 || !after.0 { before } else { after };
}
impl<'hir, R: ResolverAstLoweringExt<'hir>> ItemLowerer<'_, 'hir, R> {
fn with_lctx(
&mut self,
owner: NodeId,
f: impl FnOnce(&mut LoweringContext<'_, 'hir, R>) -> hir::OwnerNode<'hir>,
) {
let mut lctx = LoweringContext::new(self.tcx, self.resolver, self.disambiguators);
lctx.with_hir_id_owner(owner, |lctx| f(lctx));
for (def_id, info) in lctx.children {
let owner = self.owners.get_or_insert_mut(def_id);
assert!(
matches!(owner, hir::MaybeOwner::Phantom),
"duplicate copy of {def_id:?} in lctx.children"
);
*owner = info;
}
}
pub(super) fn lower_node(&mut self, def_id: LocalDefId) {
let owner = self.owners.get_or_insert_mut(def_id);
if let hir::MaybeOwner::Phantom = owner {
let node = self.ast_index[def_id];
match node {
AstOwner::NonOwner => {}
AstOwner::Crate(c) => {
assert_eq!(self.resolver.local_def_id(CRATE_NODE_ID), CRATE_DEF_ID);
self.with_lctx(CRATE_NODE_ID, |lctx| {
let module = lctx.lower_mod(&c.items, &c.spans);
// FIXME(jdonszelman): is dummy span ever a problem here?
lctx.lower_attrs(hir::CRATE_HIR_ID, &c.attrs, DUMMY_SP, Target::Crate);
hir::OwnerNode::Crate(module)
})
}
AstOwner::Item(item) => {
self.with_lctx(item.id, |lctx| hir::OwnerNode::Item(lctx.lower_item(item)))
}
AstOwner::AssocItem(item, ctxt) => {
self.with_lctx(item.id, |lctx| lctx.lower_assoc_item(item, ctxt))
}
AstOwner::ForeignItem(item) => self.with_lctx(item.id, |lctx| {
hir::OwnerNode::ForeignItem(lctx.lower_foreign_item(item))
}),
}
}
}
}
impl<'hir, R: ResolverAstLoweringExt<'hir>> LoweringContext<'_, 'hir, R> {
pub(super) fn lower_mod(
&mut self,
items: &[Box<Item>],
spans: &ModSpans,
) -> &'hir hir::Mod<'hir> {
self.arena.alloc(hir::Mod {
spans: hir::ModSpans {
inner_span: self.lower_span(spans.inner_span),
inject_use_span: self.lower_span(spans.inject_use_span),
},
item_ids: self.arena.alloc_from_iter(items.iter().flat_map(|x| self.lower_item_ref(x))),
})
}
pub(super) fn lower_item_ref(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
let mut node_ids = smallvec![hir::ItemId { owner_id: self.owner_id(i.id) }];
if let ItemKind::Use(use_tree) = &i.kind {
self.lower_item_id_use_tree(use_tree, &mut node_ids);
}
node_ids
}
fn lower_item_id_use_tree(&mut self, tree: &UseTree, vec: &mut SmallVec<[hir::ItemId; 1]>) {
match &tree.kind {
UseTreeKind::Nested { items, .. } => {
for &(ref nested, id) in items {
vec.push(hir::ItemId { owner_id: self.owner_id(id) });
self.lower_item_id_use_tree(nested, vec);
}
}
UseTreeKind::Simple(..) | UseTreeKind::Glob(_) => {}
}
}
fn lower_eii_decl(
&mut self,
id: NodeId,
name: Ident,
EiiDecl { foreign_item, impl_unsafe }: &EiiDecl,
) -> Option<hir::attrs::EiiDecl> {
self.lower_path_simple_eii(id, foreign_item).map(|did| hir::attrs::EiiDecl {
foreign_item: did,
impl_unsafe: *impl_unsafe,
name,
})
}
fn lower_eii_impl(
&mut self,
EiiImpl {
node_id,
eii_macro_path,
impl_safety,
span,
inner_span,
is_default,
known_eii_macro_resolution,
}: &EiiImpl,
) -> hir::attrs::EiiImpl {
let resolution = if let Some(target) = known_eii_macro_resolution
&& let Some(decl) = self.lower_eii_decl(
*node_id,
// the expect is ok here since we always generate this path in the eii macro.
eii_macro_path.segments.last().expect("at least one segment").ident,
target,
) {
EiiImplResolution::Known(decl)
} else if let Some(macro_did) = self.lower_path_simple_eii(*node_id, eii_macro_path) {
EiiImplResolution::Macro(macro_did)
} else {
EiiImplResolution::Error(
self.dcx().span_delayed_bug(*span, "eii never resolved without errors given"),
)
};
hir::attrs::EiiImpl {
span: self.lower_span(*span),
inner_span: self.lower_span(*inner_span),
impl_marked_unsafe: self.lower_safety(*impl_safety, hir::Safety::Safe).is_unsafe(),
is_default: *is_default,
resolution,
}
}
fn generate_extra_attrs_for_item_kind(
&mut self,
id: NodeId,
i: &ItemKind,
) -> Vec<hir::Attribute> {
match i {
ItemKind::Fn(box Fn { eii_impls, .. })
| ItemKind::Static(box StaticItem { eii_impls, .. })
if eii_impls.is_empty() =>
{
Vec::new()
}
ItemKind::Fn(box Fn { eii_impls, .. })
| ItemKind::Static(box StaticItem { eii_impls, .. }) => {
vec![hir::Attribute::Parsed(AttributeKind::EiiImpls(
eii_impls.iter().map(|i| self.lower_eii_impl(i)).collect(),
))]
}
ItemKind::MacroDef(name, MacroDef { eii_declaration: Some(target), .. }) => self
.lower_eii_decl(id, *name, target)
.map(|decl| vec![hir::Attribute::Parsed(AttributeKind::EiiDeclaration(decl))])
.unwrap_or_default(),
ItemKind::ExternCrate(..)
| ItemKind::Use(..)
| ItemKind::Const(..)
| ItemKind::ConstBlock(..)
| ItemKind::Mod(..)
| ItemKind::ForeignMod(..)
| ItemKind::GlobalAsm(..)
| ItemKind::TyAlias(..)
| ItemKind::Enum(..)
| ItemKind::Struct(..)
| ItemKind::Union(..)
| ItemKind::Trait(..)
| ItemKind::TraitAlias(..)
| ItemKind::Impl(..)
| ItemKind::MacCall(..)
| ItemKind::MacroDef(..)
| ItemKind::Delegation(..)
| ItemKind::DelegationMac(..) => Vec::new(),
}
}
fn lower_item(&mut self, i: &Item) -> &'hir hir::Item<'hir> {
let vis_span = self.lower_span(i.vis.span);
let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
let extra_hir_attributes = self.generate_extra_attrs_for_item_kind(i.id, &i.kind);
let attrs = self.lower_attrs_with_extra(
hir_id,
&i.attrs,
i.span,
Target::from_ast_item(i),
&extra_hir_attributes,
);
let kind = self.lower_item_kind(i.span, i.id, hir_id, attrs, vis_span, &i.kind);
let item = hir::Item {
owner_id: hir_id.expect_owner(),
kind,
vis_span,
span: self.lower_span(i.span),
has_delayed_lints: !self.delayed_lints.is_empty(),
eii: find_attr!(attrs, EiiImpls(..) | EiiDeclaration(..)),
};
self.arena.alloc(item)
}
fn lower_item_kind(
&mut self,
span: Span,
id: NodeId,
hir_id: hir::HirId,
attrs: &'hir [hir::Attribute],
vis_span: Span,
i: &ItemKind,
) -> hir::ItemKind<'hir> {
match i {
ItemKind::ExternCrate(orig_name, ident) => {
let ident = self.lower_ident(*ident);
hir::ItemKind::ExternCrate(*orig_name, ident)
}
ItemKind::Use(use_tree) => {
// Start with an empty prefix.
let prefix = Path {
segments: ThinVec::new(),
span: use_tree.prefix.span.shrink_to_lo(),
tokens: None,
};
self.lower_use_tree(use_tree, &prefix, id, vis_span, attrs)
}
ItemKind::Static(box ast::StaticItem {
ident,
ty,
safety: _,
mutability: m,
expr: e,
define_opaque,
eii_impls: _,
}) => {
let ident = self.lower_ident(*ident);
let ty = self
.lower_ty_alloc(ty, ImplTraitContext::Disallowed(ImplTraitPosition::StaticTy));
let body_id = self.lower_const_body(span, e.as_deref());
self.lower_define_opaque(hir_id, define_opaque);
hir::ItemKind::Static(*m, ident, ty, body_id)
}
ItemKind::Const(box ConstItem {
defaultness: _,
ident,
generics,
ty,
rhs_kind,
define_opaque,
}) => {
let ident = self.lower_ident(*ident);
let (generics, (ty, rhs)) = self.lower_generics(
generics,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
let ty = this.lower_ty_alloc(
ty,
ImplTraitContext::Disallowed(ImplTraitPosition::ConstTy),
);
let rhs = this.lower_const_item_rhs(rhs_kind, span);
(ty, rhs)
},
);
self.lower_define_opaque(hir_id, &define_opaque);
hir::ItemKind::Const(ident, generics, ty, rhs)
}
ItemKind::ConstBlock(ConstBlockItem { span, id, block }) => hir::ItemKind::Const(
self.lower_ident(ConstBlockItem::IDENT),
hir::Generics::empty(),
self.arena.alloc(self.ty_tup(DUMMY_SP, &[])),
hir::ConstItemRhs::Body({
let body = hir::Expr {
hir_id: self.lower_node_id(*id),
kind: hir::ExprKind::Block(self.lower_block(block, false), None),
span: self.lower_span(*span),
};
self.record_body(&[], body)
}),
),
ItemKind::Fn(box Fn {
sig: FnSig { decl, header, span: fn_sig_span },
ident,
generics,
body,
contract,
define_opaque,
..
}) => {
self.with_new_scopes(*fn_sig_span, |this| {
// Note: we don't need to change the return type from `T` to
// `impl Future<Output = T>` here because lower_body
// only cares about the input argument patterns in the function
// declaration (decl), not the return types.
let coroutine_kind = header.coroutine_kind;
let body_id = this.lower_maybe_coroutine_body(
*fn_sig_span,
span,
hir_id,
decl,
coroutine_kind,
body.as_deref(),
attrs,
contract.as_deref(),
header.constness,
);
let itctx = ImplTraitContext::Universal;
let (generics, decl) = this.lower_generics(generics, id, itctx, |this| {
this.lower_fn_decl(decl, id, *fn_sig_span, FnDeclKind::Fn, coroutine_kind)
});
let sig = hir::FnSig {
decl,
header: this.lower_fn_header(*header, hir::Safety::Safe, attrs),
span: this.lower_span(*fn_sig_span),
};
this.lower_define_opaque(hir_id, define_opaque);
let ident = this.lower_ident(*ident);
hir::ItemKind::Fn {
ident,
sig,
generics,
body: body_id,
has_body: body.is_some(),
}
})
}
ItemKind::Mod(_, ident, mod_kind) => {
let ident = self.lower_ident(*ident);
match mod_kind {
ModKind::Loaded(items, _, spans) => {
hir::ItemKind::Mod(ident, self.lower_mod(items, spans))
}
ModKind::Unloaded => panic!("`mod` items should have been loaded by now"),
}
}
ItemKind::ForeignMod(fm) => hir::ItemKind::ForeignMod {
abi: fm.abi.map_or(ExternAbi::FALLBACK, |abi| self.lower_abi(abi)),
items: self
.arena
.alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))),
},
ItemKind::GlobalAsm(asm) => {
let asm = self.lower_inline_asm(span, asm);
let fake_body =
self.lower_body(|this| (&[], this.expr(span, hir::ExprKind::InlineAsm(asm))));
hir::ItemKind::GlobalAsm { asm, fake_body }
}
ItemKind::TyAlias(box TyAlias { ident, generics, after_where_clause, ty, .. }) => {
// We lower
//
// type Foo = impl Trait
//
// to
//
// type Foo = Foo1
// opaque type Foo1: Trait
let ident = self.lower_ident(*ident);
let mut generics = generics.clone();
add_ty_alias_where_clause(&mut generics, after_where_clause, true);
let (generics, ty) = self.lower_generics(
&generics,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| match ty {
None => {
let guar = this.dcx().span_delayed_bug(
span,
"expected to lower type alias type, but it was missing",
);
this.arena.alloc(this.ty(span, hir::TyKind::Err(guar)))
}
Some(ty) => this.lower_ty_alloc(
ty,
ImplTraitContext::OpaqueTy {
origin: hir::OpaqueTyOrigin::TyAlias {
parent: this.local_def_id(id),
in_assoc_ty: false,
},
},
),
},
);
hir::ItemKind::TyAlias(ident, generics, ty)
}
ItemKind::Enum(ident, generics, enum_definition) => {
let ident = self.lower_ident(*ident);
let (generics, variants) = self.lower_generics(
generics,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
this.arena.alloc_from_iter(
enum_definition.variants.iter().map(|x| this.lower_variant(i, x)),
)
},
);
hir::ItemKind::Enum(ident, generics, hir::EnumDef { variants })
}
ItemKind::Struct(ident, generics, struct_def) => {
let ident = self.lower_ident(*ident);
let (generics, struct_def) = self.lower_generics(
generics,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| this.lower_variant_data(hir_id, i, struct_def),
);
hir::ItemKind::Struct(ident, generics, struct_def)
}
ItemKind::Union(ident, generics, vdata) => {
let ident = self.lower_ident(*ident);
let (generics, vdata) = self.lower_generics(
generics,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| this.lower_variant_data(hir_id, i, vdata),
);
hir::ItemKind::Union(ident, generics, vdata)
}
ItemKind::Impl(Impl {
generics: ast_generics,
of_trait,
self_ty: ty,
items: impl_items,
constness,
}) => {
// Lower the "impl header" first. This ordering is important
// for in-band lifetimes! Consider `'a` here:
//
// impl Foo<'a> for u32 {
// fn method(&'a self) { .. }
// }
//
// Because we start by lowering the `Foo<'a> for u32`
// part, we will add `'a` to the list of generics on
// the impl. When we then encounter it later in the
// method, it will not be considered an in-band
// lifetime to be added, but rather a reference to a
// parent lifetime.
let itctx = ImplTraitContext::Universal;
let (generics, (of_trait, lowered_ty)) =
self.lower_generics(ast_generics, id, itctx, |this| {
let of_trait = of_trait
.as_deref()
.map(|of_trait| this.lower_trait_impl_header(of_trait));
let lowered_ty = this.lower_ty_alloc(
ty,
ImplTraitContext::Disallowed(ImplTraitPosition::ImplSelf),
);
(of_trait, lowered_ty)
});
let new_impl_items = self
.arena
.alloc_from_iter(impl_items.iter().map(|item| self.lower_impl_item_ref(item)));
let constness = self.lower_constness(*constness);
hir::ItemKind::Impl(hir::Impl {
generics,
of_trait,
self_ty: lowered_ty,
items: new_impl_items,
constness,
})
}
ItemKind::Trait(box Trait {
constness,
is_auto,
safety,
impl_restriction,
ident,
generics,
bounds,
items,
}) => {
let constness = self.lower_constness(*constness);
let impl_restriction = self.lower_impl_restriction(impl_restriction);
let ident = self.lower_ident(*ident);
let (generics, (safety, items, bounds)) = self.lower_generics(
generics,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
let bounds = this.lower_param_bounds(
bounds,
RelaxedBoundPolicy::Forbidden(RelaxedBoundForbiddenReason::SuperTrait),
ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
);
let items = this.arena.alloc_from_iter(
items.iter().map(|item| this.lower_trait_item_ref(item)),
);
let safety = this.lower_safety(*safety, hir::Safety::Safe);
(safety, items, bounds)
},
);
hir::ItemKind::Trait(
constness,
*is_auto,
safety,
impl_restriction,
ident,
generics,
bounds,
items,
)
}
ItemKind::TraitAlias(box TraitAlias { constness, ident, generics, bounds }) => {
let constness = self.lower_constness(*constness);
let ident = self.lower_ident(*ident);
let (generics, bounds) = self.lower_generics(
generics,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
this.lower_param_bounds(
bounds,
RelaxedBoundPolicy::Forbidden(RelaxedBoundForbiddenReason::TraitAlias),
ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
)
},
);
hir::ItemKind::TraitAlias(constness, ident, generics, bounds)
}
ItemKind::MacroDef(ident, MacroDef { body, macro_rules, eii_declaration: _ }) => {
let ident = self.lower_ident(*ident);
let body = Box::new(self.lower_delim_args(body));
let def_id = self.local_def_id(id);
let def_kind = self.tcx.def_kind(def_id);
let DefKind::Macro(macro_kinds) = def_kind else {
unreachable!(
"expected DefKind::Macro for macro item, found {}",
def_kind.descr(def_id.to_def_id())
);
};
let macro_def = self.arena.alloc(ast::MacroDef {
body,
macro_rules: *macro_rules,
eii_declaration: None,
});
hir::ItemKind::Macro(ident, macro_def, macro_kinds)
}
ItemKind::Delegation(box delegation) => {
let delegation_results = self.lower_delegation(delegation, id);
hir::ItemKind::Fn {
sig: delegation_results.sig,
ident: delegation_results.ident,
generics: delegation_results.generics,
body: delegation_results.body_id,
has_body: true,
}
}
ItemKind::MacCall(..) | ItemKind::DelegationMac(..) => {
panic!("macros should have been expanded by now")
}
}
}
fn lower_path_simple_eii(&mut self, id: NodeId, path: &Path) -> Option<DefId> {
let res = self.resolver.get_partial_res(id)?;
let Some(did) = res.expect_full_res().opt_def_id() else {
self.dcx().span_delayed_bug(path.span, "should have errored in resolve");
return None;
};
Some(did)
}
#[instrument(level = "debug", skip(self))]
fn lower_use_tree(
&mut self,
tree: &UseTree,
prefix: &Path,
id: NodeId,
vis_span: Span,
attrs: &'hir [hir::Attribute],
) -> hir::ItemKind<'hir> {
let path = &tree.prefix;
let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
match tree.kind {
UseTreeKind::Simple(rename) => {
let mut ident = tree.ident();
// First, apply the prefix to the path.
let mut path = Path { segments, span: path.span, tokens: None };
// Correctly resolve `self` imports.
if path.segments.len() > 1
&& path.segments.last().unwrap().ident.name == kw::SelfLower
{
let _ = path.segments.pop();
if rename.is_none() {
ident = path.segments.last().unwrap().ident;
}
}
let res = self.lower_import_res(id, path.span);
let path = self.lower_use_path(res, &path, ParamMode::Explicit);
let ident = self.lower_ident(ident);
hir::ItemKind::Use(path, hir::UseKind::Single(ident))
}
UseTreeKind::Glob(_) => {
let res = self.expect_full_res(id);
let res = self.lower_res(res);
// Put the result in the appropriate namespace.
let res = match res {
Res::Def(DefKind::Mod | DefKind::Trait, _) => {
PerNS { type_ns: Some(res), value_ns: None, macro_ns: None }
}
Res::Def(DefKind::Enum, _) => {
PerNS { type_ns: None, value_ns: Some(res), macro_ns: None }
}
Res::Err => {
// Propagate the error to all namespaces, just to be sure.
let err = Some(Res::Err);
PerNS { type_ns: err, value_ns: err, macro_ns: err }
}
_ => span_bug!(path.span, "bad glob res {:?}", res),
};
let path = Path { segments, span: path.span, tokens: None };
let path = self.lower_use_path(res, &path, ParamMode::Explicit);
hir::ItemKind::Use(path, hir::UseKind::Glob)
}
UseTreeKind::Nested { items: ref trees, .. } => {
// Nested imports are desugared into simple imports.
// So, if we start with
//
// ```
// pub(x) use foo::{a, b};
// ```
//
// we will create three items:
//
// ```
// pub(x) use foo::a;
// pub(x) use foo::b;
// pub(x) use foo::{}; // <-- this is called the `ListStem`
// ```
//
// The first two are produced by recursively invoking
// `lower_use_tree` (and indeed there may be things
// like `use foo::{a::{b, c}}` and so forth). They
// wind up being directly added to
// `self.items`. However, the structure of this
// function also requires us to return one item, and
// for that we return the `{}` import (called the
// `ListStem`).
let span = prefix.span.to(path.span);
let prefix = Path { segments, span, tokens: None };
// Add all the nested `PathListItem`s to the HIR.
for &(ref use_tree, id) in trees {
let owner_id = self.owner_id(id);
// Each `use` import is an item and thus are owners of the
// names in the path. Up to this point the nested import is
// the current owner, since we want each desugared import to
// own its own names, we have to adjust the owner before
// lowering the rest of the import.
self.with_hir_id_owner(id, |this| {
// `prefix` is lowered multiple times, but in different HIR owners.
// So each segment gets renewed `HirId` with the same
// `ItemLocalId` and the new owner. (See `lower_node_id`)
let kind = this.lower_use_tree(use_tree, &prefix, id, vis_span, attrs);
if !attrs.is_empty() {
this.attrs.insert(hir::ItemLocalId::ZERO, attrs);
}
let item = hir::Item {
owner_id,
kind,
vis_span,
span: this.lower_span(use_tree.span()),
has_delayed_lints: !this.delayed_lints.is_empty(),
eii: find_attr!(attrs, EiiImpls(..) | EiiDeclaration(..)),
};
hir::OwnerNode::Item(this.arena.alloc(item))
});
}
// Condition should match `build_reduced_graph_for_use_tree`.
let path = if trees.is_empty()
&& !(prefix.segments.is_empty()
|| prefix.segments.len() == 1
&& prefix.segments[0].ident.name == kw::PathRoot)
{
// For empty lists we need to lower the prefix so it is checked for things
// like stability later.
let res = self.lower_import_res(id, span);
self.lower_use_path(res, &prefix, ParamMode::Explicit)
} else {
// For non-empty lists we can just drop all the data, the prefix is already
// present in HIR as a part of nested imports.
let span = self.lower_span(span);
self.arena.alloc(hir::UsePath { res: PerNS::default(), segments: &[], span })
};
hir::ItemKind::Use(path, hir::UseKind::ListStem)
}
}
}
fn lower_assoc_item(&mut self, item: &AssocItem, ctxt: AssocCtxt) -> hir::OwnerNode<'hir> {
// Evaluate with the lifetimes in `params` in-scope.
// This is used to track which lifetimes have already been defined,
// and which need to be replicated when lowering an async fn.
match ctxt {
AssocCtxt::Trait => hir::OwnerNode::TraitItem(self.lower_trait_item(item)),
AssocCtxt::Impl { of_trait } => {
hir::OwnerNode::ImplItem(self.lower_impl_item(item, of_trait))
}
}
}
fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> {
let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
let owner_id = hir_id.expect_owner();
let attrs =
self.lower_attrs(hir_id, &i.attrs, i.span, Target::from_foreign_item_kind(&i.kind));
let (ident, kind) = match &i.kind {
ForeignItemKind::Fn(box Fn { sig, ident, generics, define_opaque, .. }) => {
let fdec = &sig.decl;
let itctx = ImplTraitContext::Universal;
let (generics, (decl, fn_args)) =
self.lower_generics(generics, i.id, itctx, |this| {
(
// Disallow `impl Trait` in foreign items.
this.lower_fn_decl(fdec, i.id, sig.span, FnDeclKind::ExternFn, None),
this.lower_fn_params_to_idents(fdec),
)
});
// Unmarked safety in unsafe block defaults to unsafe.
let header = self.lower_fn_header(sig.header, hir::Safety::Unsafe, attrs);
if define_opaque.is_some() {
self.dcx().span_err(i.span, "foreign functions cannot define opaque types");
}
(
ident,
hir::ForeignItemKind::Fn(
hir::FnSig { header, decl, span: self.lower_span(sig.span) },
fn_args,
generics,
),
)
}
ForeignItemKind::Static(box StaticItem {
ident,
ty,
mutability,
expr: _,
safety,
define_opaque,
eii_impls: _,
}) => {
let ty = self
.lower_ty_alloc(ty, ImplTraitContext::Disallowed(ImplTraitPosition::StaticTy));
let safety = self.lower_safety(*safety, hir::Safety::Unsafe);
if define_opaque.is_some() {
self.dcx().span_err(i.span, "foreign statics cannot define opaque types");
}
(ident, hir::ForeignItemKind::Static(ty, *mutability, safety))
}
ForeignItemKind::TyAlias(box TyAlias { ident, .. }) => {
(ident, hir::ForeignItemKind::Type)
}
ForeignItemKind::MacCall(_) => panic!("macro shouldn't exist here"),
};
let item = hir::ForeignItem {
owner_id,
ident: self.lower_ident(*ident),
kind,
vis_span: self.lower_span(i.vis.span),
span: self.lower_span(i.span),
has_delayed_lints: !self.delayed_lints.is_empty(),
};
self.arena.alloc(item)
}
fn lower_foreign_item_ref(&mut self, i: &ForeignItem) -> hir::ForeignItemId {
hir::ForeignItemId { owner_id: self.owner_id(i.id) }
}
fn lower_variant(&mut self, item_kind: &ItemKind, v: &Variant) -> hir::Variant<'hir> {
let hir_id = self.lower_node_id(v.id);
self.lower_attrs(hir_id, &v.attrs, v.span, Target::Variant);
hir::Variant {
hir_id,
def_id: self.local_def_id(v.id),
data: self.lower_variant_data(hir_id, item_kind, &v.data),
disr_expr: v
.disr_expr
.as_ref()
.map(|e| self.lower_anon_const_to_anon_const(e, e.value.span)),
ident: self.lower_ident(v.ident),
span: self.lower_span(v.span),
}
}
fn lower_variant_data(
&mut self,
parent_id: hir::HirId,
item_kind: &ItemKind,
vdata: &VariantData,
) -> hir::VariantData<'hir> {
match vdata {
VariantData::Struct { fields, recovered } => {
let fields = self
.arena
.alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_field_def(f)));
if let ItemKind::Union(..) = item_kind {
for field in &fields[..] {
if let Some(default) = field.default {
// Unions cannot derive `Default`, and it's not clear how to use default
// field values of unions if that was supported. Therefore, blanket reject
// trying to use field values with unions.
if self.tcx.features().default_field_values() {
self.dcx().emit_err(UnionWithDefault { span: default.span });
} else {
let _ = self.dcx().span_delayed_bug(
default.span,
"expected union default field values feature gate error but none \
was produced",
);
}
}
}
}
hir::VariantData::Struct { fields, recovered: *recovered }
}
VariantData::Tuple(fields, id) => {
let ctor_id = self.lower_node_id(*id);
self.alias_attrs(ctor_id, parent_id);
let fields = self
.arena
.alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_field_def(f)));
for field in &fields[..] {
if let Some(default) = field.default {
// Default values in tuple struct and tuple variants are not allowed by the
// RFC due to concerns about the syntax, both in the item definition and the
// expression. We could in the future allow `struct S(i32 = 0);` and force
// users to construct the value with `let _ = S { .. };`.
if self.tcx.features().default_field_values() {
self.dcx().emit_err(TupleStructWithDefault { span: default.span });
} else {
let _ = self.dcx().span_delayed_bug(
default.span,
"expected `default values on `struct` fields aren't supported` \
feature-gate error but none was produced",
);
}
}
}
hir::VariantData::Tuple(fields, ctor_id, self.local_def_id(*id))
}
VariantData::Unit(id) => {
let ctor_id = self.lower_node_id(*id);
self.alias_attrs(ctor_id, parent_id);
hir::VariantData::Unit(ctor_id, self.local_def_id(*id))
}
}
}
pub(super) fn lower_field_def(
&mut self,
(index, f): (usize, &FieldDef),
) -> hir::FieldDef<'hir> {
let ty =
self.lower_ty_alloc(&f.ty, ImplTraitContext::Disallowed(ImplTraitPosition::FieldTy));
let hir_id = self.lower_node_id(f.id);
self.lower_attrs(hir_id, &f.attrs, f.span, Target::Field);
hir::FieldDef {
span: self.lower_span(f.span),
hir_id,
def_id: self.local_def_id(f.id),
ident: match f.ident {
Some(ident) => self.lower_ident(ident),
// FIXME(jseyfried): positional field hygiene.
None => Ident::new(sym::integer(index), self.lower_span(f.span)),
},
vis_span: self.lower_span(f.vis.span),
default: f
.default
.as_ref()
.map(|v| self.lower_anon_const_to_anon_const(v, v.value.span)),
ty,
safety: self.lower_safety(f.safety, hir::Safety::Safe),
}
}
fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> {
let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
let attrs = self.lower_attrs(
hir_id,
&i.attrs,
i.span,
Target::from_assoc_item_kind(&i.kind, AssocCtxt::Trait),
);
let trait_item_def_id = hir_id.expect_owner();
let (ident, generics, kind, has_value) = match &i.kind {
AssocItemKind::Const(box ConstItem {
ident,
generics,
ty,
rhs_kind,
define_opaque,
..
}) => {
let (generics, kind) = self.lower_generics(
generics,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
let ty = this.lower_ty_alloc(
ty,
ImplTraitContext::Disallowed(ImplTraitPosition::ConstTy),
);
// Trait associated consts don't need an expression/body.
let rhs = if rhs_kind.has_expr() {
Some(this.lower_const_item_rhs(rhs_kind, i.span))
} else {
None
};
hir::TraitItemKind::Const(ty, rhs, rhs_kind.is_type_const().into())
},
);
if define_opaque.is_some() {
if rhs_kind.has_expr() {
self.lower_define_opaque(hir_id, &define_opaque);
} else {
self.dcx().span_err(
i.span,
"only trait consts with default bodies can define opaque types",
);
}
}
(*ident, generics, kind, rhs_kind.has_expr())
}
AssocItemKind::Fn(box Fn {
sig, ident, generics, body: None, define_opaque, ..
}) => {
// FIXME(contracts): Deny contract here since it won't apply to
// any impl method or callees.
let idents = self.lower_fn_params_to_idents(&sig.decl);
let (generics, sig) = self.lower_method_sig(
generics,
sig,
i.id,
FnDeclKind::Trait,
sig.header.coroutine_kind,
attrs,
);
if define_opaque.is_some() {
self.dcx().span_err(
i.span,
"only trait methods with default bodies can define opaque types",
);
}
(
*ident,
generics,
hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(idents)),
false,
)
}
AssocItemKind::Fn(box Fn {
sig,
ident,
generics,
body: Some(body),
contract,
define_opaque,
..
}) => {
let body_id = self.lower_maybe_coroutine_body(
sig.span,
i.span,
hir_id,
&sig.decl,
sig.header.coroutine_kind,
Some(body),
attrs,
contract.as_deref(),
sig.header.constness,
);
let (generics, sig) = self.lower_method_sig(
generics,
sig,
i.id,
FnDeclKind::Trait,
sig.header.coroutine_kind,
attrs,
);
self.lower_define_opaque(hir_id, &define_opaque);
(
*ident,
generics,
hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)),
true,
)
}
AssocItemKind::Type(box TyAlias {
ident,
generics,
after_where_clause,
bounds,
ty,
..
}) => {
let mut generics = generics.clone();
add_ty_alias_where_clause(&mut generics, after_where_clause, false);
let (generics, kind) = self.lower_generics(
&generics,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
let ty = ty.as_ref().map(|x| {
this.lower_ty_alloc(
x,
ImplTraitContext::Disallowed(ImplTraitPosition::AssocTy),
)
});
hir::TraitItemKind::Type(
this.lower_param_bounds(
bounds,
RelaxedBoundPolicy::Allowed,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
),
ty,
)
},
);
(*ident, generics, kind, ty.is_some())
}
AssocItemKind::Delegation(box delegation) => {
let delegation_results = self.lower_delegation(delegation, i.id);
let item_kind = hir::TraitItemKind::Fn(
delegation_results.sig,
hir::TraitFn::Provided(delegation_results.body_id),
);
(delegation.ident, delegation_results.generics, item_kind, true)
}
AssocItemKind::MacCall(..) | AssocItemKind::DelegationMac(..) => {
panic!("macros should have been expanded by now")
}
};
let defaultness = match i.kind.defaultness() {
// We do not yet support `final` on trait associated items other than functions.
// Even though we reject `final` on non-functions during AST validation, we still
// need to stop propagating it here because later compiler passes do not expect
// and cannot handle such items.
Defaultness::Final(..) if !matches!(i.kind, AssocItemKind::Fn(..)) => {
Defaultness::Implicit
}
defaultness => defaultness,
};
let (defaultness, _) = self
.lower_defaultness(defaultness, has_value, || hir::Defaultness::Default { has_value });
let item = hir::TraitItem {
owner_id: trait_item_def_id,
ident: self.lower_ident(ident),
generics,
kind,
span: self.lower_span(i.span),
defaultness,
has_delayed_lints: !self.delayed_lints.is_empty(),
};
self.arena.alloc(item)
}
fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemId {
hir::TraitItemId { owner_id: self.owner_id(i.id) }
}
/// Construct `ExprKind::Err` for the given `span`.
pub(crate) fn expr_err(&mut self, span: Span, guar: ErrorGuaranteed) -> hir::Expr<'hir> {
self.expr(span, hir::ExprKind::Err(guar))
}
fn lower_trait_impl_header(
&mut self,
trait_impl_header: &TraitImplHeader,
) -> &'hir hir::TraitImplHeader<'hir> {
let TraitImplHeader { safety, polarity, defaultness, ref trait_ref } = *trait_impl_header;
let safety = self.lower_safety(safety, hir::Safety::Safe);
let polarity = match polarity {
ImplPolarity::Positive => ImplPolarity::Positive,
ImplPolarity::Negative(s) => ImplPolarity::Negative(self.lower_span(s)),
};
// `defaultness.has_value()` is never called for an `impl`, always `true` in order
// to not cause an assertion failure inside the `lower_defaultness` function.
let has_val = true;
let (defaultness, defaultness_span) =
self.lower_defaultness(defaultness, has_val, || hir::Defaultness::Final);
let modifiers = TraitBoundModifiers {
constness: BoundConstness::Never,
asyncness: BoundAsyncness::Normal,
// we don't use this in bound lowering
polarity: BoundPolarity::Positive,
};
let trait_ref = self.lower_trait_ref(
modifiers,
trait_ref,
ImplTraitContext::Disallowed(ImplTraitPosition::Trait),
);
self.arena.alloc(hir::TraitImplHeader {
safety,
polarity,
defaultness,
defaultness_span,
trait_ref,
})
}
fn lower_impl_item(
&mut self,
i: &AssocItem,
is_in_trait_impl: bool,
) -> &'hir hir::ImplItem<'hir> {
// Since `default impl` is not yet implemented, this is always true in impls.
let has_value = true;
let (defaultness, _) =
self.lower_defaultness(i.kind.defaultness(), has_value, || hir::Defaultness::Final);
let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
let attrs = self.lower_attrs(
hir_id,
&i.attrs,
i.span,
Target::from_assoc_item_kind(&i.kind, AssocCtxt::Impl { of_trait: is_in_trait_impl }),
);
let (ident, (generics, kind)) = match &i.kind {
AssocItemKind::Const(box ConstItem {
ident,
generics,
ty,
rhs_kind,
define_opaque,
..
}) => (
*ident,
self.lower_generics(
generics,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
let ty = this.lower_ty_alloc(
ty,
ImplTraitContext::Disallowed(ImplTraitPosition::ConstTy),
);
this.lower_define_opaque(hir_id, &define_opaque);
let rhs = this.lower_const_item_rhs(rhs_kind, i.span);
hir::ImplItemKind::Const(ty, rhs)
},
),
),
AssocItemKind::Fn(box Fn {
sig,
ident,
generics,
body,
contract,
define_opaque,
..
}) => {
let body_id = self.lower_maybe_coroutine_body(
sig.span,
i.span,
hir_id,
&sig.decl,
sig.header.coroutine_kind,
body.as_deref(),
attrs,
contract.as_deref(),
sig.header.constness,
);
let (generics, sig) = self.lower_method_sig(
generics,
sig,
i.id,
if is_in_trait_impl { FnDeclKind::Impl } else { FnDeclKind::Inherent },
sig.header.coroutine_kind,
attrs,
);
self.lower_define_opaque(hir_id, &define_opaque);
(*ident, (generics, hir::ImplItemKind::Fn(sig, body_id)))
}
AssocItemKind::Type(box TyAlias {
ident, generics, after_where_clause, ty, ..
}) => {
let mut generics = generics.clone();
add_ty_alias_where_clause(&mut generics, after_where_clause, false);
(
*ident,
self.lower_generics(
&generics,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| match ty {
None => {
let guar = this.dcx().span_delayed_bug(
i.span,
"expected to lower associated type, but it was missing",
);
let ty = this.arena.alloc(this.ty(i.span, hir::TyKind::Err(guar)));
hir::ImplItemKind::Type(ty)
}
Some(ty) => {
let ty = this.lower_ty_alloc(
ty,
ImplTraitContext::OpaqueTy {
origin: hir::OpaqueTyOrigin::TyAlias {
parent: this.local_def_id(i.id),
in_assoc_ty: true,
},
},
);
hir::ImplItemKind::Type(ty)
}
},
),
)
}
AssocItemKind::Delegation(box delegation) => {
let delegation_results = self.lower_delegation(delegation, i.id);
(
delegation.ident,
(
delegation_results.generics,
hir::ImplItemKind::Fn(delegation_results.sig, delegation_results.body_id),
),
)
}
AssocItemKind::MacCall(..) | AssocItemKind::DelegationMac(..) => {
panic!("macros should have been expanded by now")
}
};
let span = self.lower_span(i.span);
let item = hir::ImplItem {
owner_id: hir_id.expect_owner(),
ident: self.lower_ident(ident),
generics,
impl_kind: if is_in_trait_impl {
ImplItemImplKind::Trait {
defaultness,
trait_item_def_id: self
.resolver
.get_partial_res(i.id)
.and_then(|r| r.expect_full_res().opt_def_id())
.ok_or_else(|| {
self.dcx().span_delayed_bug(
span,
"could not resolve trait item being implemented",
)
}),
}
} else {
ImplItemImplKind::Inherent { vis_span: self.lower_span(i.vis.span) }
},
kind,
span,
has_delayed_lints: !self.delayed_lints.is_empty(),
};
self.arena.alloc(item)
}
fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemId {
hir::ImplItemId { owner_id: self.owner_id(i.id) }
}
fn lower_defaultness(
&self,
d: Defaultness,
has_value: bool,
implicit: impl FnOnce() -> hir::Defaultness,
) -> (hir::Defaultness, Option<Span>) {
match d {
Defaultness::Implicit => (implicit(), None),
Defaultness::Default(sp) => {
(hir::Defaultness::Default { has_value }, Some(self.lower_span(sp)))
}
Defaultness::Final(sp) => (hir::Defaultness::Final, Some(self.lower_span(sp))),
}
}
fn record_body(
&mut self,
params: &'hir [hir::Param<'hir>],
value: hir::Expr<'hir>,
) -> hir::BodyId {
let body = hir::Body { params, value: self.arena.alloc(value) };
let id = body.id();
assert_eq!(id.hir_id.owner, self.current_hir_id_owner);
self.bodies.push((id.hir_id.local_id, self.arena.alloc(body)));
id
}
pub(super) fn lower_body(
&mut self,
f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>),
) -> hir::BodyId {
let prev_coroutine_kind = self.coroutine_kind.take();
let prev_is_in_const_context = mem::take(&mut self.is_in_const_context);
let task_context = self.task_context.take();
let (parameters, result) = f(self);
let body_id = self.record_body(parameters, result);
self.task_context = task_context;
self.coroutine_kind = prev_coroutine_kind;
self.is_in_const_context = prev_is_in_const_context;
body_id
}
fn lower_param(&mut self, param: &Param) -> hir::Param<'hir> {
let hir_id = self.lower_node_id(param.id);
self.lower_attrs(hir_id, &param.attrs, param.span, Target::Param);
hir::Param {
hir_id,
pat: self.lower_pat(&param.pat),
ty_span: self.lower_span(param.ty.span),
span: self.lower_span(param.span),
}
}
pub(super) fn lower_fn_body(
&mut self,
decl: &FnDecl,
contract: Option<&FnContract>,
constness: Const,
body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
) -> hir::BodyId {
self.lower_body(|this| {
if let Const::Yes(_) = constness {
this.is_in_const_context = true;
}
let params =
this.arena.alloc_from_iter(decl.inputs.iter().map(|x| this.lower_param(x)));
// Optionally lower the fn contract
if let Some(contract) = contract {
(params, this.lower_contract(body, contract))
} else {
(params, body(this))
}
})
}
fn lower_fn_body_block(
&mut self,
decl: &FnDecl,
body: &Block,
contract: Option<&FnContract>,
constness: Const,
) -> hir::BodyId {
self.lower_fn_body(decl, contract, constness, |this| this.lower_block_expr(body))
}
pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
self.lower_body(|this| {
(
&[],
match expr {
Some(expr) => {
this.is_in_const_context = true;
this.lower_expr_mut(expr)
}
None => this.expr_err(span, this.dcx().span_delayed_bug(span, "no block")),
},
)
})
}
/// Takes what may be the body of an `async fn` or a `gen fn` and wraps it in an `async {}` or
/// `gen {}` block as appropriate.
fn lower_maybe_coroutine_body(
&mut self,
fn_decl_span: Span,
span: Span,
fn_id: hir::HirId,
decl: &FnDecl,
coroutine_kind: Option<CoroutineKind>,
body: Option<&Block>,
attrs: &'hir [hir::Attribute],
contract: Option<&FnContract>,
constness: Const,
) -> hir::BodyId {
let Some(body) = body else {
// Functions without a body are an error, except if this is an intrinsic. For those we
// create a fake body so that the entire rest of the compiler doesn't have to deal with
// this as a special case.
return self.lower_fn_body(decl, contract, constness, |this| {
if find_attr!(attrs, RustcIntrinsic) || this.tcx.is_sdylib_interface_build() {
let span = this.lower_span(span);
let empty_block = hir::Block {
hir_id: this.next_id(),
stmts: &[],
expr: None,
rules: hir::BlockCheckMode::DefaultBlock,
span,
targeted_by_break: false,
};
let loop_ = hir::ExprKind::Loop(
this.arena.alloc(empty_block),
None,
hir::LoopSource::Loop,
span,
);
hir::Expr { hir_id: this.next_id(), kind: loop_, span }
} else {
this.expr_err(span, this.dcx().has_errors().unwrap())
}
});
};
let Some(coroutine_kind) = coroutine_kind else {
// Typical case: not a coroutine.
return self.lower_fn_body_block(decl, body, contract, constness);
};
// FIXME(contracts): Support contracts on async fn.
self.lower_body(|this| {
let (parameters, expr) = this.lower_coroutine_body_with_moved_arguments(
decl,
|this| this.lower_block_expr(body),
fn_decl_span,
body.span,
coroutine_kind,
hir::CoroutineSource::Fn,
);
// FIXME(async_fn_track_caller): Can this be moved above?
let hir_id = expr.hir_id;
this.maybe_forward_track_caller(body.span, fn_id, hir_id);
(parameters, expr)
})
}
/// Lowers a desugared coroutine body after moving all of the arguments
/// into the body. This is to make sure that the future actually owns the
/// arguments that are passed to the function, and to ensure things like
/// drop order are stable.
pub(crate) fn lower_coroutine_body_with_moved_arguments(
&mut self,
decl: &FnDecl,
lower_body: impl FnOnce(&mut LoweringContext<'_, 'hir, R>) -> hir::Expr<'hir>,
fn_decl_span: Span,
body_span: Span,
coroutine_kind: CoroutineKind,
coroutine_source: hir::CoroutineSource,
) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>) {
let mut parameters: Vec<hir::Param<'_>> = Vec::new();
let mut statements: Vec<hir::Stmt<'_>> = Vec::new();
// Async function parameters are lowered into the closure body so that they are
// captured and so that the drop order matches the equivalent non-async functions.
//
// from:
//
// async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
// <body>
// }
//
// into:
//
// fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
// async move {
// let __arg2 = __arg2;
// let <pattern> = __arg2;
// let __arg1 = __arg1;
// let <pattern> = __arg1;
// let __arg0 = __arg0;
// let <pattern> = __arg0;
// drop-temps { <body> } // see comments later in fn for details
// }
// }
//
// If `<pattern>` is a simple ident, then it is lowered to a single
// `let <pattern> = <pattern>;` statement as an optimization.
//
// Note that the body is embedded in `drop-temps`; an
// equivalent desugaring would be `return { <body>
// };`. The key point is that we wish to drop all the
// let-bound variables and temporaries created in the body
// (and its tail expression!) before we drop the
// parameters (c.f. rust-lang/rust#64512).
for (index, parameter) in decl.inputs.iter().enumerate() {
let parameter = self.lower_param(parameter);
let span = parameter.pat.span;
// Check if this is a binding pattern, if so, we can optimize and avoid adding a
// `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
let (ident, is_simple_parameter) = match parameter.pat.kind {
hir::PatKind::Binding(hir::BindingMode(ByRef::No, _), _, ident, _) => (ident, true),
// For `ref mut` or wildcard arguments, we can't reuse the binding, but
// we can keep the same name for the parameter.
// This lets rustdoc render it correctly in documentation.
hir::PatKind::Binding(_, _, ident, _) => (ident, false),
hir::PatKind::Wild => (Ident::with_dummy_span(rustc_span::kw::Underscore), false),
_ => {
// Replace the ident for bindings that aren't simple.
let name = format!("__arg{index}");
let ident = Ident::from_str(&name);
(ident, false)
}
};
let desugared_span = self.mark_span_with_reason(DesugaringKind::Async, span, None);
// Construct a parameter representing `__argN: <ty>` to replace the parameter of the
// async function.
//
// If this is the simple case, this parameter will end up being the same as the
// original parameter, but with a different pattern id.
let stmt_attrs = self.attrs.get(&parameter.hir_id.local_id).copied();
let (new_parameter_pat, new_parameter_id) = self.pat_ident(desugared_span, ident);
let new_parameter = hir::Param {
hir_id: parameter.hir_id,
pat: new_parameter_pat,
ty_span: self.lower_span(parameter.ty_span),
span: self.lower_span(parameter.span),
};
if is_simple_parameter {
// If this is the simple case, then we only insert one statement that is
// `let <pat> = <pat>;`. We re-use the original argument's pattern so that
// `HirId`s are densely assigned.
let expr = self.expr_ident(desugared_span, ident, new_parameter_id);
let stmt = self.stmt_let_pat(
stmt_attrs,
desugared_span,
Some(expr),
parameter.pat,
hir::LocalSource::AsyncFn,
);
statements.push(stmt);
} else {
// If this is not the simple case, then we construct two statements:
//
// ```
// let __argN = __argN;
// let <pat> = __argN;
// ```
//
// The first statement moves the parameter into the closure and thus ensures
// that the drop order is correct.
//
// The second statement creates the bindings that the user wrote.
// Construct the `let mut __argN = __argN;` statement. It must be a mut binding
// because the user may have specified a `ref mut` binding in the next
// statement.
let (move_pat, move_id) =
self.pat_ident_binding_mode(desugared_span, ident, hir::BindingMode::MUT);
let move_expr = self.expr_ident(desugared_span, ident, new_parameter_id);
let move_stmt = self.stmt_let_pat(
None,
desugared_span,
Some(move_expr),
move_pat,
hir::LocalSource::AsyncFn,
);
// Construct the `let <pat> = __argN;` statement. We re-use the original
// parameter's pattern so that `HirId`s are densely assigned.
let pattern_expr = self.expr_ident(desugared_span, ident, move_id);
let pattern_stmt = self.stmt_let_pat(
stmt_attrs,
desugared_span,
Some(pattern_expr),
parameter.pat,
hir::LocalSource::AsyncFn,
);
statements.push(move_stmt);
statements.push(pattern_stmt);
};
parameters.push(new_parameter);
}
let mkbody = |this: &mut LoweringContext<'_, 'hir, R>| {
// Create a block from the user's function body:
let user_body = lower_body(this);
// Transform into `drop-temps { <user-body> }`, an expression:
let desugared_span =
this.mark_span_with_reason(DesugaringKind::Async, user_body.span, None);
let user_body = this.expr_drop_temps(desugared_span, this.arena.alloc(user_body));
// As noted above, create the final block like
//
// ```
// {
// let $param_pattern = $raw_param;
// ...
// drop-temps { <user-body> }
// }
// ```
let body = this.block_all(
desugared_span,
this.arena.alloc_from_iter(statements),
Some(user_body),
);
this.expr_block(body)
};
let desugaring_kind = match coroutine_kind {
CoroutineKind::Async { .. } => hir::CoroutineDesugaring::Async,
CoroutineKind::Gen { .. } => hir::CoroutineDesugaring::Gen,
CoroutineKind::AsyncGen { .. } => hir::CoroutineDesugaring::AsyncGen,
};
let closure_id = coroutine_kind.closure_id();
let coroutine_expr = self.make_desugared_coroutine_expr(
// The default capture mode here is by-ref. Later on during upvar analysis,
// we will force the captured arguments to by-move, but for async closures,
// we want to make sure that we avoid unnecessarily moving captures, or else
// all async closures would default to `FnOnce` as their calling mode.
CaptureBy::Ref,
closure_id,
None,
fn_decl_span,
body_span,
desugaring_kind,
coroutine_source,
mkbody,
);
let expr = hir::Expr {
hir_id: self.lower_node_id(closure_id),
kind: coroutine_expr,
span: self.lower_span(body_span),
};
(self.arena.alloc_from_iter(parameters), expr)
}
fn lower_method_sig(
&mut self,
generics: &Generics,
sig: &FnSig,
id: NodeId,
kind: FnDeclKind,
coroutine_kind: Option<CoroutineKind>,
attrs: &[hir::Attribute],
) -> (&'hir hir::Generics<'hir>, hir::FnSig<'hir>) {
let header = self.lower_fn_header(sig.header, hir::Safety::Safe, attrs);
let itctx = ImplTraitContext::Universal;
let (generics, decl) = self.lower_generics(generics, id, itctx, |this| {
this.lower_fn_decl(&sig.decl, id, sig.span, kind, coroutine_kind)
});
(generics, hir::FnSig { header, decl, span: self.lower_span(sig.span) })
}
pub(super) fn lower_fn_header(
&mut self,
h: FnHeader,
default_safety: hir::Safety,
attrs: &[hir::Attribute],
) -> hir::FnHeader {
let asyncness = if let Some(CoroutineKind::Async { span, .. }) = h.coroutine_kind {
hir::IsAsync::Async(self.lower_span(span))
} else {
hir::IsAsync::NotAsync
};
let safety = self.lower_safety(h.safety, default_safety);
// Treat safe `#[target_feature]` functions as unsafe, but also remember that we did so.
let safety = if find_attr!(attrs, TargetFeature { was_forced: false, .. })
&& safety.is_safe()
&& !self.tcx.sess.target.is_like_wasm
{
hir::HeaderSafety::SafeTargetFeatures
} else {
safety.into()
};
hir::FnHeader {
safety,
asyncness,
constness: self.lower_constness(h.constness),
abi: self.lower_extern(h.ext),
}
}
pub(super) fn lower_abi(&mut self, abi_str: StrLit) -> ExternAbi {
let ast::StrLit { symbol_unescaped, span, .. } = abi_str;
let extern_abi = symbol_unescaped.as_str().parse().unwrap_or_else(|_| {
self.error_on_invalid_abi(abi_str);
ExternAbi::Rust
});
let tcx = self.tcx;
// we can't do codegen for unsupported ABIs, so error now so we won't get farther
if !tcx.sess.target.is_abi_supported(extern_abi) {
let mut err = struct_span_code_err!(
tcx.dcx(),
span,
E0570,
"{extern_abi} is not a supported ABI for the current target",
);
if let ExternAbi::Stdcall { unwind } = extern_abi {
let c_abi = ExternAbi::C { unwind };
let system_abi = ExternAbi::System { unwind };
err.help(format!("if you need `extern {extern_abi}` on win32 and `extern {c_abi}` everywhere else, \
use `extern {system_abi}`"
));
}
err.emit();
}
// Show required feature gate even if we already errored, as the user is likely to build the code
// for the actually intended target next and then they will need the feature gate.
gate_unstable_abi(tcx.sess, tcx.features(), span, extern_abi);
extern_abi
}
pub(super) fn lower_extern(&mut self, ext: Extern) -> ExternAbi {
match ext {
Extern::None => ExternAbi::Rust,
Extern::Implicit(_) => ExternAbi::FALLBACK,
Extern::Explicit(abi, _) => self.lower_abi(abi),
}
}
fn error_on_invalid_abi(&self, abi: StrLit) {
let abi_names = enabled_names(self.tcx.features(), abi.span)
.iter()
.map(|s| Symbol::intern(s))
.collect::<Vec<_>>();
let suggested_name = find_best_match_for_name(&abi_names, abi.symbol_unescaped, None);
self.dcx().emit_err(InvalidAbi {
abi: abi.symbol_unescaped,
span: abi.span,
suggestion: suggested_name.map(|suggested_name| InvalidAbiSuggestion {
span: abi.span,
suggestion: suggested_name.to_string(),
}),
command: "rustc --print=calling-conventions".to_string(),
});
}
pub(super) fn lower_constness(&mut self, c: Const) -> hir::Constness {
match c {
Const::Yes(_) => hir::Constness::Const,
Const::No => hir::Constness::NotConst,
}
}
pub(super) fn lower_safety(&self, s: Safety, default: hir::Safety) -> hir::Safety {
match s {
Safety::Unsafe(_) => hir::Safety::Unsafe,
Safety::Default => default,
Safety::Safe(_) => hir::Safety::Safe,
}
}
pub(super) fn lower_impl_restriction(
&mut self,
r: &ImplRestriction,
) -> &'hir hir::ImplRestriction<'hir> {
let kind = match &r.kind {
RestrictionKind::Unrestricted => hir::RestrictionKind::Unrestricted,
RestrictionKind::Restricted { path, id, shorthand: _ } => {
let res = self.resolver.get_partial_res(*id);
if let Some(did) = res.and_then(|res| res.expect_full_res().opt_def_id()) {
hir::RestrictionKind::Restricted(self.arena.alloc(hir::Path {
res: did,
segments: self.arena.alloc_from_iter(path.segments.iter().map(|segment| {
self.lower_path_segment(
path.span,
segment,
ParamMode::Explicit,
GenericArgsMode::Err,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
)
})),
span: self.lower_span(path.span),
}))
} else {
self.dcx().span_delayed_bug(path.span, "should have errored in resolve");
hir::RestrictionKind::Unrestricted
}
}
};
self.arena.alloc(hir::ImplRestriction { kind, span: self.lower_span(r.span) })
}
/// Return the pair of the lowered `generics` as `hir::Generics` and the evaluation of `f` with
/// the carried impl trait definitions and bounds.
#[instrument(level = "debug", skip(self, f))]
fn lower_generics<T>(
&mut self,
generics: &Generics,
parent_node_id: NodeId,
itctx: ImplTraitContext,
f: impl FnOnce(&mut Self) -> T,
) -> (&'hir hir::Generics<'hir>, T) {
assert!(self.impl_trait_defs.is_empty());
assert!(self.impl_trait_bounds.is_empty());
let mut predicates: SmallVec<[hir::WherePredicate<'hir>; 4]> = SmallVec::new();
predicates.extend(generics.params.iter().filter_map(|param| {
self.lower_generic_bound_predicate(
param.ident,
param.id,
&param.kind,
&param.bounds,
param.colon_span,
generics.span,
RelaxedBoundPolicy::Allowed,
itctx,
PredicateOrigin::GenericParam,
)
}));
predicates.extend(
generics
.where_clause
.predicates
.iter()
.map(|predicate| self.lower_where_predicate(predicate, &generics.params)),
);
let mut params: SmallVec<[hir::GenericParam<'hir>; 4]> = self
.lower_generic_params_mut(&generics.params, hir::GenericParamSource::Generics)
.collect();
// Introduce extra lifetimes if late resolution tells us to.
let extra_lifetimes = self.resolver.extra_lifetime_params(parent_node_id);
params.extend(extra_lifetimes.into_iter().filter_map(|(ident, node_id, res)| {
self.lifetime_res_to_generic_param(
ident,
node_id,
res,
hir::GenericParamSource::Generics,
)
}));
let has_where_clause_predicates = !generics.where_clause.predicates.is_empty();
let where_clause_span = self.lower_span(generics.where_clause.span);
let span = self.lower_span(generics.span);
let res = f(self);
let impl_trait_defs = std::mem::take(&mut self.impl_trait_defs);
params.extend(impl_trait_defs.into_iter());
let impl_trait_bounds = std::mem::take(&mut self.impl_trait_bounds);
predicates.extend(impl_trait_bounds.into_iter());
let lowered_generics = self.arena.alloc(hir::Generics {
params: self.arena.alloc_from_iter(params),
predicates: self.arena.alloc_from_iter(predicates),
has_where_clause_predicates,
where_clause_span,
span,
});
(lowered_generics, res)
}
pub(super) fn lower_define_opaque(
&mut self,
hir_id: HirId,
define_opaque: &Option<ThinVec<(NodeId, Path)>>,
) {
assert_eq!(self.define_opaque, None);
assert!(hir_id.is_owner());
let Some(define_opaque) = define_opaque.as_ref() else {
return;
};
let define_opaque = define_opaque.iter().filter_map(|(id, path)| {
let res = self.resolver.get_partial_res(*id);
let Some(did) = res.and_then(|res| res.expect_full_res().opt_def_id()) else {
self.dcx().span_delayed_bug(path.span, "should have errored in resolve");
return None;
};
let Some(did) = did.as_local() else {
self.dcx().span_err(
path.span,
"only opaque types defined in the local crate can be defined",
);
return None;
};
Some((self.lower_span(path.span), did))
});
let define_opaque = self.arena.alloc_from_iter(define_opaque);
self.define_opaque = Some(define_opaque);
}
pub(super) fn lower_generic_bound_predicate(
&mut self,
ident: Ident,
id: NodeId,
kind: &GenericParamKind,
bounds: &[GenericBound],
colon_span: Option<Span>,
parent_span: Span,
rbp: RelaxedBoundPolicy<'_>,
itctx: ImplTraitContext,
origin: PredicateOrigin,
) -> Option<hir::WherePredicate<'hir>> {
// Do not create a clause if we do not have anything inside it.
if bounds.is_empty() {
return None;
}
let bounds = self.lower_param_bounds(bounds, rbp, itctx);
let param_span = ident.span;
// Reconstruct the span of the entire predicate from the individual generic bounds.
let span_start = colon_span.unwrap_or_else(|| param_span.shrink_to_hi());
let span = bounds.iter().fold(span_start, |span_accum, bound| {
match bound.span().find_ancestor_inside(parent_span) {
Some(bound_span) => span_accum.to(bound_span),
None => span_accum,
}
});
let span = self.lower_span(span);
let hir_id = self.next_id();
let kind = self.arena.alloc(match kind {
GenericParamKind::Const { .. } => return None,
GenericParamKind::Type { .. } => {
let def_id = self.local_def_id(id).to_def_id();
let hir_id = self.next_id();
let res = Res::Def(DefKind::TyParam, def_id);
let ident = self.lower_ident(ident);
let ty_path = self.arena.alloc(hir::Path {
span: self.lower_span(param_span),
res,
segments: self
.arena
.alloc_from_iter([hir::PathSegment::new(ident, hir_id, res)]),
});
let ty_id = self.next_id();
let bounded_ty =
self.ty_path(ty_id, param_span, hir::QPath::Resolved(None, ty_path));
hir::WherePredicateKind::BoundPredicate(hir::WhereBoundPredicate {
bounded_ty: self.arena.alloc(bounded_ty),
bounds,
bound_generic_params: &[],
origin,
})
}
GenericParamKind::Lifetime => {
let lt_id = self.next_node_id();
let lifetime =
self.new_named_lifetime(id, lt_id, ident, LifetimeSource::Other, ident.into());
hir::WherePredicateKind::RegionPredicate(hir::WhereRegionPredicate {
lifetime,
bounds,
in_where_clause: false,
})
}
});
Some(hir::WherePredicate { hir_id, span, kind })
}
fn lower_where_predicate(
&mut self,
pred: &WherePredicate,
params: &[ast::GenericParam],
) -> hir::WherePredicate<'hir> {
let hir_id = self.lower_node_id(pred.id);
let span = self.lower_span(pred.span);
self.lower_attrs(hir_id, &pred.attrs, span, Target::WherePredicate);
let kind = self.arena.alloc(match &pred.kind {
WherePredicateKind::BoundPredicate(WhereBoundPredicate {
bound_generic_params,
bounded_ty,
bounds,
}) => {
let rbp = if bound_generic_params.is_empty() {
RelaxedBoundPolicy::AllowedIfOnTyParam(bounded_ty.id, params)
} else {
RelaxedBoundPolicy::Forbidden(RelaxedBoundForbiddenReason::LateBoundVarsInScope)
};
hir::WherePredicateKind::BoundPredicate(hir::WhereBoundPredicate {
bound_generic_params: self.lower_generic_params(
bound_generic_params,
hir::GenericParamSource::Binder,
),
bounded_ty: self.lower_ty_alloc(
bounded_ty,
ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
),
bounds: self.lower_param_bounds(
bounds,
rbp,
ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
),
origin: PredicateOrigin::WhereClause,
})
}
WherePredicateKind::RegionPredicate(WhereRegionPredicate { lifetime, bounds }) => {
hir::WherePredicateKind::RegionPredicate(hir::WhereRegionPredicate {
lifetime: self.lower_lifetime(
lifetime,
LifetimeSource::Other,
lifetime.ident.into(),
),
bounds: self.lower_param_bounds(
bounds,
RelaxedBoundPolicy::Allowed,
ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
),
in_where_clause: true,
})
}
WherePredicateKind::EqPredicate(WhereEqPredicate { lhs_ty, rhs_ty }) => {
hir::WherePredicateKind::EqPredicate(hir::WhereEqPredicate {
lhs_ty: self.lower_ty_alloc(
lhs_ty,
ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
),
rhs_ty: self.lower_ty_alloc(
rhs_ty,
ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
),
})
}
});
hir::WherePredicate { hir_id, span, kind }
}
}
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