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Auto merge of #113847 - SparrowLii:path_clone, r=cjgillot

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avoid clone path prefix when lowering to hir

Found this while trying to parallelize `lower_to_hir`.

When lowering to hir, `Nested` paths in `ast` will be split and the prefix segments will be cloned. This could be omited, since the only consequence is that the prefix segments in `Path`s in hir will have the same `HirId`s, and it seems harmless.

This simplifies the process of lowering to hir and avoids re-modification of `ResolverAstLowering`.

r? `@Aaron1011`
cc #99292
This commit is contained in:
bors 2023-07-21 11:02:47 +00:00
commit c06b2b9117
2 changed files with 3 additions and 21 deletions
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14
compiler/rustc_ast_lowering/src/item.rs
View File

@ -551,17 +551,6 @@ fn lower_use_tree(
for &(ref use_tree, id) in trees { for &(ref use_tree, id) in trees {
let new_hir_id = self.local_def_id(id); let new_hir_id = self.local_def_id(id);
let mut prefix = prefix.clone();
// Give the segments new node-ids since they are being cloned.
for seg in &mut prefix.segments {
// Give the cloned segment the same resolution information
// as the old one (this is needed for stability checking).
let new_id = self.next_node_id();
self.resolver.clone_res(seg.id, new_id);
seg.id = new_id;
}
// Each `use` import is an item and thus are owners of the // Each `use` import is an item and thus are owners of the
// names in the path. Up to this point the nested import is // names in the path. Up to this point the nested import is
// the current owner, since we want each desugared import to // the current owner, since we want each desugared import to
@ -570,6 +559,9 @@ fn lower_use_tree(
self.with_hir_id_owner(id, |this| { self.with_hir_id_owner(id, |this| {
let mut ident = *ident; let mut ident = *ident;
// `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 = let kind =
this.lower_use_tree(use_tree, &prefix, id, vis_span, &mut ident, attrs); this.lower_use_tree(use_tree, &prefix, id, vis_span, &mut ident, attrs);
if let Some(attrs) = attrs { if let Some(attrs) = attrs {

10
compiler/rustc_ast_lowering/src/lib.rs
View File

@ -148,10 +148,6 @@ trait ResolverAstLoweringExt {
fn legacy_const_generic_args(&self, expr: &Expr) -> Option<Vec<usize>>; fn legacy_const_generic_args(&self, expr: &Expr) -> Option<Vec<usize>>;
fn get_partial_res(&self, id: NodeId) -> Option<PartialRes>; fn get_partial_res(&self, id: NodeId) -> Option<PartialRes>;
fn get_import_res(&self, id: NodeId) -> PerNS<Option<Res<NodeId>>>; fn get_import_res(&self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
// Clones the resolution (if any) on 'source' and applies it
// to 'target'. Used when desugaring a `UseTreeKind::Nested` to
// multiple `UseTreeKind::Simple`s
fn clone_res(&mut self, source: NodeId, target: NodeId);
fn get_label_res(&self, id: NodeId) -> Option<NodeId>; fn get_label_res(&self, id: NodeId) -> Option<NodeId>;
fn get_lifetime_res(&self, id: NodeId) -> Option<LifetimeRes>; fn get_lifetime_res(&self, id: NodeId) -> Option<LifetimeRes>;
fn take_extra_lifetime_params(&mut self, id: NodeId) -> Vec<(Ident, NodeId, LifetimeRes)>; fn take_extra_lifetime_params(&mut self, id: NodeId) -> Vec<(Ident, NodeId, LifetimeRes)>;
@ -184,12 +180,6 @@ fn legacy_const_generic_args(&self, expr: &Expr) -> Option<Vec<usize>> {
None None
} }
fn clone_res(&mut self, source: NodeId, target: NodeId) {
if let Some(res) = self.partial_res_map.get(&source) {
self.partial_res_map.insert(target, *res);
}
}
/// Obtains resolution for a `NodeId` with a single resolution. /// Obtains resolution for a `NodeId` with a single resolution.
fn get_partial_res(&self, id: NodeId) -> Option<PartialRes> { fn get_partial_res(&self, id: NodeId) -> Option<PartialRes> {
self.partial_res_map.get(&id).copied() self.partial_res_map.get(&id).copied()