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Rollup merge of #123344 - pietroalbini:pa-unused-imports, r=Nilstrieb

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Remove braces when fixing a nested use tree into a single item

[Back in 2019](https://github.com/rust-lang/rust/pull/56645) I added rustfix support for the `unused_imports` lint, to automatically remove them when running `cargo fix`. For the most part this worked great, but when removing all but one childs of a nested use tree it turned `use foo::{Unused, Used}` into `use foo::{Used}`. This is slightly annoying, because it then requires you to run `rustfmt` to get `use foo::Used`.

This PR automatically removes braces and the surrouding whitespace when all but one child of a nested use tree are unused. To get it done I had to add the span of the nested use tree to the AST, and refactor a bit the code I wrote back then.

A thing I noticed is, there doesn't seem to be any `//@ run-rustfix` test for fixing the `unused_imports` lint. I created a test in `tests/suggestions` (is that the right directory?) that for now tests just what I added in the PR. I can followup in a separate PR to add more tests for fixing `unused_lints`.

This PR is best reviewed commit-by-commit.
This commit is contained in:
Matthias Krüger 2024-05-08 23:33:24 +02:00 • committed by GitHub
commit d30af5e168
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20 changed files with 194 additions and 60 deletions
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6
compiler/rustc_ast_lowering/src/item.rs
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@ -135,8 +135,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
fn lower_item_id_use_tree(&mut self, tree: &UseTree, vec: &mut SmallVec<[hir::ItemId; 1]>) {
match &tree.kind {
UseTreeKind::Nested(nested_vec) => {
for &(ref nested, id) in nested_vec {
UseTreeKind::Nested { items, .. } => {
for &(ref nested, id) in items {
vec.push(hir::ItemId {
owner_id: hir::OwnerId { def_id: self.local_def_id(id) },
});
@ -518,7 +518,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let path = self.lower_use_path(res, &path, ParamMode::Explicit);
hir::ItemKind::Use(path, hir::UseKind::Glob)
}
UseTreeKind::Nested(ref trees) => {
UseTreeKind::Nested { items: ref trees, .. } => {
// Nested imports are desugared into simple imports.
// So, if we start with
//