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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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2
compiler/rustc_ast/src/ast.rs
View file

@ -2729,7 +2729,7 @@ pub enum UseTreeKind {
/// `use prefix` or `use prefix as rename`
Simple(Option<Ident>),
/// `use prefix::{...}`
Nested(ThinVec<(UseTree, NodeId)>),
Nested { items: ThinVec<(UseTree, NodeId)>, span: Span },
/// `use prefix::*`
Glob,
}

2
compiler/rustc_ast/src/mut_visit.rs
View file

@ -441,7 +441,7 @@ fn noop_visit_use_tree<T: MutVisitor>(use_tree: &mut UseTree, vis: &mut T) {
vis.visit_path(prefix);
match kind {
UseTreeKind::Simple(rename) => visit_opt(rename, |rename| vis.visit_ident(rename)),
UseTreeKind::Nested(items) => {
UseTreeKind::Nested { items, .. } => {
for (tree, id) in items {
vis.visit_use_tree(tree);
vis.visit_id(id);

4
compiler/rustc_ast/src/visit.rs
View file

@ -517,8 +517,8 @@ pub fn walk_use_tree<'a, V: Visitor<'a>>(
visit_opt!(visitor, visit_ident, rename);
}
UseTreeKind::Glob => {}
UseTreeKind::Nested(ref use_trees) => {
for &(ref nested_tree, nested_id) in use_trees {
UseTreeKind::Nested { ref items, .. } => {
for &(ref nested_tree, nested_id) in items {
try_visit!(visitor.visit_use_tree(nested_tree, nested_id, true));
}
}