bjoernager/rust
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remove braces when fixing a nested use tree into a single use

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This commit is contained in:
Pietro Albini 2024-04-14 18:40:49 +02:00
parent 13f76235b3
commit 2d3a9a5847
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GPG key ID: 3E06ABE80BAAF19C
4 changed files with 135 additions and 1 deletions
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27
compiler/rustc_resolve/src/check_unused.rs
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@ -292,7 +292,7 @@ fn calc_unused_spans(
UnusedSpanResult::Used
}
}
ast::UseTreeKind::Nested { items: ref nested, .. } => {
ast::UseTreeKind::Nested { items: ref nested, span: tree_span } => {
if nested.is_empty() {
return UnusedSpanResult::Unused { spans: vec![use_tree.span], remove: full_span };
}
@ -300,6 +300,7 @@ fn calc_unused_spans(
let mut unused_spans = Vec::new();
let mut to_remove = Vec::new();
let mut used_childs = 0;
let mut contains_self = false;
let mut previous_unused = false;
for (pos, (use_tree, use_tree_id)) in nested.iter().enumerate() {
let remove = match calc_unused_spans(unused_import, use_tree, *use_tree_id) {
@ -339,6 +340,8 @@ fn calc_unused_spans(
to_remove.push(remove_span);
}
}
contains_self |= use_tree.prefix == kw::SelfLower
&& matches!(use_tree.kind, ast::UseTreeKind::Simple(None));
previous_unused = remove.is_some();
}
if unused_spans.is_empty() {
@ -346,6 +349,28 @@ fn calc_unused_spans(
} else if used_childs == 0 {
UnusedSpanResult::Unused { spans: unused_spans, remove: full_span }
} else {
// If there is only one remaining child that is used, the braces around the use
// tree are not needed anymore. In that case, we determine the span of the left
// brace and the right brace, and tell rustfix to remove them as well.
//
// This means that `use a::{B, C};` will be turned into `use a::B;` rather than
// `use a::{B};`, removing a rustfmt roundtrip.
//
// Note that we cannot remove the braces if the only item inside the use tree is
// `self`: `use foo::{self};` is valid Rust syntax, while `use foo::self;` errors
// out. We also cannot turn `use foo::{self}` into `use foo`, as the former doesn't
// import types with the same name as the module.
if used_childs == 1 && !contains_self {
// Left brace, from the start of the nested group to the first item.
to_remove.push(
tree_span.shrink_to_lo().to(nested.first().unwrap().0.span.shrink_to_lo()),
);
// Right brace, from the end of the last item to the end of the nested group.
to_remove.push(
nested.last().unwrap().0.span.shrink_to_hi().to(tree_span.shrink_to_hi()),
);
}
UnusedSpanResult::PartialUnused { spans: unused_spans, remove: to_remove }
}
}