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Merged
rust-bors merged 7 commits into from
Sep 19, 2026
Merged

More AST lowering cleanups #162950

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9e7d4b2
Don't double-allocate `OwnerInfo`
nnethercote Sep 1, 2026
9a03326
Convert some `&mut self` to `&self` in the lowerer
nnethercote Sep 1, 2026
990c292
Reduce the scope of a local
nnethercote Sep 1, 2026
9b817c5
Rename `LoweringContext::current_item`
nnethercote Sep 1, 2026
3ee39bd
Fix an inconsistent comment
nnethercote Sep 1, 2026
6e7d014
Inline and remove `lower_delim_args`
nnethercote Sep 1, 2026
11b373e
Eliminate `ItemLowerer`
nnethercote Sep 1, 2026
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4 changes: 2 additions & 2 deletions compiler/rustc_ast_lowering/src/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1018,7 +1018,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
expr.span,
hir::ExprKind::Err(self.dcx().emit_err(AwaitOnlyInAsyncFnAndBlocks {
await_kw_span,
item_span: self.current_item,
item_span: self.current_item_span,
})),
);
return hir::ExprKind::Block(
Expand Down Expand Up @@ -1712,7 +1712,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
Some(hir::CoroutineKind::Coroutine(_)) => false,
None => {
let suggestion = self.current_item.map(|s| s.shrink_to_lo());
let suggestion = self.current_item_span.map(|s| s.shrink_to_lo());
self.dcx().emit_err(YieldInClosure { span, suggestion });
self.coroutine_kind = Some(hir::CoroutineKind::Coroutine(Movability::Movable));

Expand Down
68 changes: 9 additions & 59 deletions compiler/rustc_ast_lowering/src/item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,11 +5,8 @@ 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::{
self as hir, CRATE_OWNER_ID, HirId, ImplItemImplKind, LifetimeSource, PredicateOrigin, Target,
find_attr,
self as hir, HirId, ImplItemImplKind, LifetimeSource, PredicateOrigin, Target, find_attr,
};
use rustc_middle::middle::resolve::ResolverAstLowering;
use rustc_middle::ty::TyCtxt;
use rustc_middle::ty::data_structures::IndexMap;
use rustc_span::def_id::{DefId, LocalDefId};
use rustc_span::edit_distance::find_best_match_for_name;
Expand All @@ -28,14 +25,9 @@ use super::{
};
use crate::diagnostics::{ConstComptimeFn, ResolvingRestrictionKind, RestrictionAncestorOnly};

pub(super) struct ItemLowerer<'a, 'hir> {
pub(super) tcx: TyCtxt<'hir>,
pub(super) resolver: &'a ResolverAstLowering<'hir>,
}

/// 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.
/// 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,
Expand All @@ -52,48 +44,6 @@ fn add_ty_alias_where_clause(
if before.0 || !after.0 { before } else { after };
}

impl<'hir> ItemLowerer<'_, 'hir> {
fn with_lctx(
&mut self,
owner: NodeId,
f: impl FnOnce(&mut LoweringContext<'_, 'hir>) -> hir::OwnerNode<'hir>,
) -> hir::MaybeOwner<'hir> {
let mut lctx = LoweringContext::new(self.tcx, self.resolver, owner);

let item = f(&mut lctx);

let info = lctx.curr_owner.into_owner_info(self.tcx, item);
hir::MaybeOwner::Owner(lctx.arena.alloc(info))
}

#[instrument(level = "debug", skip(self, c))]
pub(super) fn lower_crate(&mut self, c: &Crate) -> hir::MaybeOwner<'hir> {
self.with_lctx(CRATE_NODE_ID, |lctx| {
debug_assert_eq!(lctx.curr_owner.owner_id(), CRATE_OWNER_ID);
let module = lctx.lower_mod(&c.items, &c.spans);
lctx.lower_attrs(hir::CRATE_HIR_ID, &c.attrs, c.spans.inner_span, Target::Crate);
hir::OwnerNode::Crate(module)
})
}

#[instrument(level = "debug", skip(self))]
pub(super) fn lower_item(&mut self, item: &Item) -> hir::MaybeOwner<'hir> {
self.with_lctx(item.id, |lctx| hir::OwnerNode::Item(lctx.lower_item(item)))
}

pub(super) fn lower_trait_item(&mut self, item: &AssocItem) -> hir::MaybeOwner<'hir> {
self.with_lctx(item.id, |lctx| hir::OwnerNode::TraitItem(lctx.lower_trait_item(item)))
}

pub(super) fn lower_impl_item(&mut self, item: &AssocItem) -> hir::MaybeOwner<'hir> {
self.with_lctx(item.id, |lctx| hir::OwnerNode::ImplItem(lctx.lower_impl_item(item)))
}

pub(super) fn lower_foreign_item(&mut self, item: &ForeignItem) -> hir::MaybeOwner<'hir> {
self.with_lctx(item.id, |lctx| hir::OwnerNode::ForeignItem(lctx.lower_foreign_item(item)))
}
}

impl<'hir> LoweringContext<'_, 'hir> {
pub(super) fn lower_mod(
&mut self,
Expand Down Expand Up @@ -203,7 +153,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
}

fn lower_item(&mut self, i: &Item) -> &'hir hir::Item<'hir> {
pub(super) fn lower_item(&mut self, i: &Item) -> &'hir hir::Item<'hir> {
let owner_id = self.curr_owner.owner_id();
let hir_id: HirId = owner_id.into();
let vis_span = self.lower_span(i.vis.span);
Expand Down Expand Up @@ -544,7 +494,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
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 body = body.clone();
let def_id = self.curr_owner.owner.def_id;
let def_kind = self.tcx.def_kind(def_id);
let DefKind::Macro(macro_kinds) = def_kind else {
Expand Down Expand Up @@ -730,7 +680,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
}

fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> {
pub(super) fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> {
let owner_id = self.curr_owner.owner_id();
let hir_id: HirId = owner_id.into();
let attrs =
Expand Down Expand Up @@ -911,7 +861,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
}

fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> {
pub(super) fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> {
let trait_item_def_id = self.curr_owner.owner_id();
let hir_id: HirId = trait_item_def_id.into();
let attrs = self.lower_attrs(
Expand Down Expand Up @@ -1160,7 +1110,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
ident
}

fn lower_impl_item(&mut self, i: &AssocItem) -> &'hir hir::ImplItem<'hir> {
pub(super) fn lower_impl_item(&mut self, i: &AssocItem) -> &'hir hir::ImplItem<'hir> {
let owner_id = self.curr_owner.owner_id();
let hir_id: HirId = owner_id.into();
let parent_id = self.tcx.local_parent(owner_id.def_id);
Expand Down
71 changes: 44 additions & 27 deletions compiler/rustc_ast_lowering/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,8 +60,9 @@ use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId, LocalDefIdMap};
use rustc_hir::definitions::PerParentDisambiguatorState;
use rustc_hir::lints::DelayedLint;
use rustc_hir::{
self as hir, AngleBrackets, ConstArg, GenericArg, HirId, ItemLocalMap, LifetimeSource,
LifetimeSyntax, MissingLifetimeKind, ParamName, Target, TraitCandidate, find_attr,
self as hir, AngleBrackets, CRATE_OWNER_ID, ConstArg, GenericArg, HirId, ItemLocalMap,
LifetimeSource, LifetimeSyntax, MissingLifetimeKind, ParamName, Target, TraitCandidate,
find_attr,
};
use rustc_index::{Idx, IndexSlice, IndexVec};
use rustc_macros::extension;
Expand Down Expand Up @@ -296,7 +297,7 @@ struct LoweringContext<'a, 'hir> {

/// Used to get the current `fn`'s def span to point to when using `await`
/// outside of an `async fn`.
current_item: Option<Span>,
current_item_span: Option<Span>,

try_block_scope: TryBlockScope,
loop_scope: Option<HirId>,
Expand Down Expand Up @@ -366,7 +367,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
is_in_dyn_type: false,
coroutine_kind: None,
task_context: None,
current_item: None,
current_item_span: None,

move_expr_bindings: Vec::new(),
lowering_move_expr_initializer: false,
Expand Down Expand Up @@ -783,15 +784,37 @@ fn lower_to_hir(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::MaybeOwner<'_> {
return fallback_to_ancestor(tcx.local_parent(def_id));
};

let mut item_lowerer = item::ItemLowerer { tcx, resolver: &*resolver };
fn with_lctx<'hir>(
tcx: TyCtxt<'hir>,
resolver: &ResolverAstLowering<'hir>,
owner: NodeId,
f: impl FnOnce(&mut LoweringContext<'_, 'hir>) -> hir::OwnerNode<'hir>,
) -> hir::MaybeOwner<'hir> {
let mut lctx = LoweringContext::new(tcx, resolver, owner);
let item = f(&mut lctx);
hir::MaybeOwner::Owner(lctx.curr_owner.into_owner_info(tcx, item))
}

let item = match &node {
// The item existed in the AST.
AstOwner::Crate(c) => item_lowerer.lower_crate(&c),
AstOwner::Item(item) => item_lowerer.lower_item(&item),
AstOwner::TraitItem(item) => item_lowerer.lower_trait_item(&item),
AstOwner::ImplItem(item) => item_lowerer.lower_impl_item(&item),
AstOwner::ForeignItem(item) => item_lowerer.lower_foreign_item(&item),
AstOwner::Crate(c) => with_lctx(tcx, &*resolver, CRATE_NODE_ID, |lctx| {
debug_assert_eq!(lctx.curr_owner.owner_id(), CRATE_OWNER_ID);
let module = lctx.lower_mod(&c.items, &c.spans);
lctx.lower_attrs(hir::CRATE_HIR_ID, &c.attrs, c.spans.inner_span, Target::Crate);
hir::OwnerNode::Crate(module)
}),
AstOwner::Item(item) => {
with_lctx(tcx, &*resolver, item.id, |lctx| hir::OwnerNode::Item(lctx.lower_item(item)))
}
AstOwner::TraitItem(item) => with_lctx(tcx, &*resolver, item.id, |lctx| {
hir::OwnerNode::TraitItem(lctx.lower_trait_item(item))
}),
AstOwner::ImplItem(item) => with_lctx(tcx, &*resolver, item.id, |lctx| {
hir::OwnerNode::ImplItem(lctx.lower_impl_item(item))
}),
AstOwner::ForeignItem(item) => with_lctx(tcx, &*resolver, item.id, |lctx| {
hir::OwnerNode::ForeignItem(lctx.lower_foreign_item(item))
}),
AstOwner::NestedUseTree(owner_id) => fallback_to_ancestor(*owner_id),
// The item existed in the AST, but is not a HIR owner.
// Fetch the correct information from its parent.
Expand Down Expand Up @@ -824,7 +847,7 @@ enum GenericArgsMode {
ParenSugar,
/// Allow RTN, don't allow paren sugar.
ReturnTypeNotation,
// Error if parenthesized generics or RTN are encountered.
/// Error if parenthesized generics or RTN are encountered.
Err,
/// Silence errors when lowering generics. Only used with `Res::Err`.
Silence,
Expand Down Expand Up @@ -982,7 +1005,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}

#[instrument(level = "trace", skip(self))]
fn lower_res(&mut self, res: Res<NodeId>) -> Res {
fn lower_res(&self, res: Res<NodeId>) -> Res {
let res: Result<Res, ()> = res.apply_id(|id| {
let owner = self.curr_owner.owner_id();
let local_id =
Expand All @@ -999,11 +1022,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
res.unwrap_or(Res::Err)
}

fn expect_full_res(&mut self, id: NodeId) -> Res<NodeId> {
fn expect_full_res(&self, id: NodeId) -> Res<NodeId> {
self.get_partial_res(id).map_or(Res::Err, |pr| pr.expect_full_res())
}

fn lower_import_res(&mut self, id: NodeId, span: Span) -> PerNS<Option<Res>> {
fn lower_import_res(&self, id: NodeId, span: Span) -> PerNS<Option<Res>> {
debug_assert_eq!(id, self.curr_owner.owner.id);
let per_ns = self.curr_owner.owner.import_res.map(|res| res.map(|res| self.lower_res(res)));
if per_ns.is_empty() {
Expand Down Expand Up @@ -1154,8 +1177,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
}

fn with_new_scopes<T>(&mut self, scope_span: Span, f: impl FnOnce(&mut Self) -> T) -> T {
let current_item = self.current_item;
self.current_item = Some(scope_span);
let current_item_span = self.current_item_span;
self.current_item_span = Some(scope_span);

let was_in_loop_condition = self.is_in_loop_condition;
self.is_in_loop_condition = false;
Expand All @@ -1172,7 +1195,7 @@ impl<'hir> LoweringContext<'_, 'hir> {

self.is_in_loop_condition = was_in_loop_condition;

self.current_item = current_item;
self.current_item_span = current_item_span;

ret
}
Expand Down Expand Up @@ -1261,10 +1284,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
}

fn lower_delim_args(&self, args: &DelimArgs) -> DelimArgs {
args.clone()
}

/// Lower an associated item constraint.
#[instrument(level = "debug", skip_all)]
fn lower_assoc_item_constraint(
Expand Down Expand Up @@ -1647,8 +1666,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.lower_array_length_to_const_arg(length),
),
TyKind::TraitObject(bounds, kind) => {
let mut lifetime_bound = None;
let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
let mut lifetime_bound = None;
let bounds =
this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| match bound {
// We can safely ignore constness here since AST validation
Expand Down Expand Up @@ -1681,9 +1700,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
None
}
}));
let lifetime_bound =
lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span));
(bounds, lifetime_bound)
(bounds, lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span)))
});
hir::TyKind::TraitObject(bounds, TaggedRef::new(lifetime_bound, *kind))
}
Expand Down Expand Up @@ -3058,15 +3075,15 @@ impl<'hir> LoweringContext<'_, 'hir> {
}))
}

fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
fn lower_unsafe_source(&self, u: UnsafeSource) -> hir::UnsafeSource {
match u {
CompilerGenerated => hir::UnsafeSource::CompilerGenerated,
UserProvided => hir::UnsafeSource::UserProvided,
}
}

fn lower_trait_bound_modifiers(
&mut self,
&self,
modifiers: TraitBoundModifiers,
) -> hir::TraitBoundModifiers {
let constness = match modifiers.constness {
Expand Down
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