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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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4
compiler/rustc_lint/src/unused.rs
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@ -1501,7 +1501,7 @@ declare_lint_pass!(UnusedImportBraces => [UNUSED_IMPORT_BRACES]);
impl UnusedImportBraces {
fn check_use_tree(&self, cx: &EarlyContext<'_>, use_tree: &ast::UseTree, item: &ast::Item) {
if let ast::UseTreeKind::Nested(ref items) = use_tree.kind {
if let ast::UseTreeKind::Nested { ref items, .. } = use_tree.kind {
// Recursively check nested UseTrees
for (tree, _) in items {
self.check_use_tree(cx, tree, item);
@ -1522,7 +1522,7 @@ impl UnusedImportBraces {
rename.unwrap_or(orig_ident).name
}
ast::UseTreeKind::Glob => Symbol::intern("*"),
ast::UseTreeKind::Nested(_) => return,
ast::UseTreeKind::Nested { .. } => return,
};
cx.emit_span_lint(