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Auto merge of #120609 - petrochenkov:nousestem2, r=<try>
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hir: Stop keeping prefixes for most of `use` list stems

And make sure all other imports have non-empty resolution lists.

Addresses one of FIXMEs in #120206.
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bors committed Feb 3, 2024
2 parents bf3c6c5 + f5d6eb3 commit bae4968
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Showing 3 changed files with 23 additions and 9 deletions.
19 changes: 13 additions & 6 deletions compiler/rustc_ast_lowering/src/item.rs
Original file line number Diff line number Diff line change
Expand Up @@ -496,8 +496,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
}

let res =
self.expect_full_res_from_use(id).map(|res| self.lower_res(res)).collect();
let res = self.lower_import_res(id, path.span);
let path = self.lower_use_path(res, &path, ParamMode::Explicit);
hir::ItemKind::Use(path, hir::UseKind::Single)
}
Expand Down Expand Up @@ -533,7 +532,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
// for that we return the `{}` import (called the
// `ListStem`).

let prefix = Path { segments, span: prefix.span.to(path.span), tokens: None };
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 {
Expand Down Expand Up @@ -567,9 +567,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
});
}

let res =
self.expect_full_res_from_use(id).map(|res| self.lower_res(res)).collect();
let path = self.lower_use_path(res, &prefix, ParamMode::Explicit);
let path = if trees.is_empty() && !prefix.segments.is_empty() {
// 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.
self.arena.alloc(hir::UsePath { res: smallvec![], segments: &[], span })
};
hir::ItemKind::Use(path, hir::UseKind::ListStem)
}
}
Expand Down
12 changes: 9 additions & 3 deletions compiler/rustc_ast_lowering/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,7 @@ use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
use rustc_session::parse::{add_feature_diagnostics, feature_err};
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{DesugaringKind, Span, DUMMY_SP};
use smallvec::SmallVec;
use smallvec::{smallvec, SmallVec};
use std::collections::hash_map::Entry;
use thin_vec::ThinVec;

Expand Down Expand Up @@ -749,8 +749,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
self.resolver.get_partial_res(id).map_or(Res::Err, |pr| pr.expect_full_res())
}

fn expect_full_res_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Res<NodeId>> {
self.resolver.get_import_res(id).present_items()
fn lower_import_res(&mut self, id: NodeId, span: Span) -> SmallVec<[Res; 3]> {
let res = self.resolver.get_import_res(id).present_items();
let res: SmallVec<_> = res.map(|res| self.lower_res(res)).collect();
if res.is_empty() {
self.dcx().span_delayed_bug(span, "no resolution for an import");
return smallvec![Res::Err];
}
res
}

fn make_lang_item_qpath(&mut self, lang_item: hir::LangItem, span: Span) -> hir::QPath<'hir> {
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_ast_lowering/src/path.rs
Original file line number Diff line number Diff line change
Expand Up @@ -156,6 +156,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
p: &Path,
param_mode: ParamMode,
) -> &'hir hir::UsePath<'hir> {
assert!((1..=3).contains(&res.len()));
self.arena.alloc(hir::UsePath {
res,
segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
Expand Down

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