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Overhaul UsePath.

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`UsePath` contains a `SmallVec<[Res; 3]>`. This holds up to three `Res`
results, one per namespace (type, value, or macro). `lower_import_res`
takes a `PerNS<Option<Res<NodeId>>>` result and lowers it into the
`SmallVec`. This is pretty weird. The input `PerNS` makes it clear which
`Res` belongs to which namespace, but the `SmallVec` throws that
information away.

And code that operates on the `SmallVec` tends to use iteration (or even
just grabbing the first entry!) without knowing which namespace the
`Res` belongs to. Even weirder! Also, `SmallVec` is an overly flexible
type to use here, because it can contain any number of elements (even
though it's optimized for 3 in this case).

This commit changes `UsePath` so it also contains a
`PerNS<Option<Res<HirId>>>`. This type preserves more information and is
more self-documenting. The commit also changes a lot of the use sites to
access the result for a particular namespace. E.g. if you're looking up
a trait, it will be in the `Res` for the type namespace if it's present;
it's silly to look in the `Res` for the value namespace or macro
namespace. Overall I find the new code much easier to understand.

However, some use sites still iterate. These now use `present_items`
because that filters out the `None` results.

Also, `redundant_pub_crate.rs` gets a bigger change. A
`UseKind:ListStem` item gets no `Res` results, which means the old `all`
call in `is_not_macro_export` would succeed (because `all` succeeds on
an empty iterator) and the `ListStem` would be ignored. This is what we
want, but was more by luck than design. The new code detects `ListStem`
explicitly. The commit generalizes the name of that function
accordingly.

Finally, the commit also removes the `use_path` arena, because
`PerNS<Option<Res>>` impls `Copy` (unlike `SmallVec`) and it can be
allocated in the arena shared by all `Copy` types.
This commit is contained in:
Nicholas Nethercote 2025-05-30 01:37:48 +10:00
parent 176c34a946
commit 8747ccbcdf
23 changed files with 112 additions and 86 deletions
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4
src/librustdoc/clean/mod.rs
View file

@ -1606,7 +1606,7 @@ fn first_non_private<'tcx>(
&& let hir::Node::Item(item) = cx.tcx.hir_node_by_def_id(local_use_def_id)
&& let hir::ItemKind::Use(path, hir::UseKind::Single(_)) = item.kind
{
for res in &path.res {
for res in path.res.present_items() {
if let Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) = res {
continue;
}
@ -3014,7 +3014,7 @@ fn clean_use_statement<'tcx>(
) -> Vec<Item> {
let mut items = Vec::new();
let hir::UsePath { segments, ref res, span } = *path;
for &res in res {
for res in res.present_items() {
let path = hir::Path { segments, res, span };
items.append(&mut clean_use_statement_inner(import, name, &path, kind, cx, inlined_names));
}

2
src/librustdoc/visit_ast.rs
View file

@ -440,7 +440,7 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
hir::ItemKind::GlobalAsm { .. } => {}
hir::ItemKind::Use(_, hir::UseKind::ListStem) => {}
hir::ItemKind::Use(path, kind) => {
for &res in &path.res {
for res in path.res.present_items() {
// Struct and variant constructors and proc macro stubs always show up alongside
// their definitions, we've already processed them so just discard these.
if should_ignore_res(res) {