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Auto merge of #56645 - pietroalbini:fix-unused-imports, r=estebank

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Initial implementation of rustfixable unused_imports lint

This PR adds the initial implementation of rustfixable `unused_imports` lint. The implementation works, but rustfix is not able to apply all the suggestions until https://github.com/rust-lang/rust/issues/53934 is fixed. It also needs https://github.com/rust-lang/rust/pull/58296 to hide the suggested note since it's really useless.

cc https://github.com/rust-lang/rust/issues/47888

<details><summary><code>cargo fix</code> in action on the <code>unused_imports</code> lint</summary>

![screenshot from 2018-12-09 15-49-01](https://user-images.githubusercontent.com/2299951/49698874-3a026080-fbca-11e8-9bf1-24060b6c59c8.png)

</details>
This commit is contained in:
bors 2019-02-11 10:34:09 +00:00
commit 57d7cfc3cf
15 changed files with 228 additions and 51 deletions
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10
src/librustc/lint/builtin.rs
View File

@ -473,6 +473,7 @@ pub enum BuiltinLintDiagnostics {
MacroExpandedMacroExportsAccessedByAbsolutePaths(Span),
ElidedLifetimesInPaths(usize, Span, bool, Span, String),
UnknownCrateTypes(Span, String, String),
UnusedImports(String, Vec<(Span, String)>),
}
impl BuiltinLintDiagnostics {
@ -554,6 +555,15 @@ impl BuiltinLintDiagnostics {
BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
}
BuiltinLintDiagnostics::UnusedImports(message, replaces) => {
if !replaces.is_empty() {
db.multipart_suggestion(
&message,
replaces,
Applicability::MachineApplicable,
);
}
}
}
}
}

203
src/librustc_resolve/check_unused.rs
View File

@ -7,23 +7,52 @@
//
// Unused trait imports can't be checked until the method resolution. We save
// candidates here, and do the actual check in librustc_typeck/check_unused.rs.
//
// Checking for unused imports is split into three steps:
//
// - `UnusedImportCheckVisitor` walks the AST to find all the unused imports
// inside of `UseTree`s, recording their `NodeId`s and grouping them by
// the parent `use` item
//
// - `calc_unused_spans` then walks over all the `use` items marked in the
// previous step to collect the spans associated with the `NodeId`s and to
// calculate the spans that can be removed by rustfix; This is done in a
// separate step to be able to collapse the adjacent spans that rustfix
// will remove
//
// - `check_crate` finally emits the diagnostics based on the data generated
// in the last step
use std::ops::{Deref, DerefMut};
use crate::Resolver;
use crate::resolve_imports::ImportDirectiveSubclass;
use rustc::{lint, ty};
use rustc::util::nodemap::NodeMap;
use rustc::{lint, ty};
use rustc_data_structures::fx::FxHashSet;
use syntax::ast;
use syntax::visit::{self, Visitor};
use syntax_pos::{Span, MultiSpan, DUMMY_SP};
struct UnusedImport<'a> {
use_tree: &'a ast::UseTree,
use_tree_id: ast::NodeId,
item_span: Span,
unused: FxHashSet<ast::NodeId>,
}
impl<'a> UnusedImport<'a> {
fn add(&mut self, id: ast::NodeId) {
self.unused.insert(id);
}
}
struct UnusedImportCheckVisitor<'a, 'b: 'a> {
resolver: &'a mut Resolver<'b>,
/// All the (so far) unused imports, grouped path list
unused_imports: NodeMap<NodeMap<Span>>,
unused_imports: NodeMap<UnusedImport<'a>>,
base_use_tree: Option<&'a ast::UseTree>,
base_id: ast::NodeId,
item_span: Span,
}
@ -46,7 +75,7 @@ impl<'a, 'b> DerefMut for UnusedImportCheckVisitor<'a, 'b> {
impl<'a, 'b> UnusedImportCheckVisitor<'a, 'b> {
// We have information about whether `use` (import) directives are actually
// used now. If an import is not used at all, we signal a lint error.
fn check_import(&mut self, item_id: ast::NodeId, id: ast::NodeId, span: Span) {
fn check_import(&mut self, id: ast::NodeId) {
let mut used = false;
self.per_ns(|this, ns| used |= this.used_imports.contains(&(id, ns)));
if !used {
@ -54,16 +83,31 @@ impl<'a, 'b> UnusedImportCheckVisitor<'a, 'b> {
// Check later.
return;
}
self.unused_imports.entry(item_id).or_default().insert(id, span);
self.unused_import(self.base_id).add(id);
} else {
// This trait import is definitely used, in a way other than
// method resolution.
self.maybe_unused_trait_imports.remove(&id);
if let Some(i) = self.unused_imports.get_mut(&item_id) {
i.remove(&id);
if let Some(i) = self.unused_imports.get_mut(&self.base_id) {
i.unused.remove(&id);
}
}
}
fn unused_import(&mut self, id: ast::NodeId) -> &mut UnusedImport<'a> {
let use_tree_id = self.base_id;
let use_tree = self.base_use_tree.unwrap();
let item_span = self.item_span;
self.unused_imports
.entry(id)
.or_insert_with(|| UnusedImport {
use_tree,
use_tree_id,
item_span,
unused: FxHashSet::default(),
})
}
}
impl<'a, 'b> Visitor<'a> for UnusedImportCheckVisitor<'a, 'b> {
@ -88,31 +132,112 @@ impl<'a, 'b> Visitor<'a> for UnusedImportCheckVisitor<'a, 'b> {
// This allows the grouping of all the lints in the same item
if !nested {
self.base_id = id;
self.base_use_tree = Some(use_tree);
}
if let ast::UseTreeKind::Nested(ref items) = use_tree.kind {
// If it's the parent group, cover the entire use item
let span = if nested {
use_tree.span
} else {
self.item_span
};
if items.is_empty() {
self.unused_imports
.entry(self.base_id)
.or_default()
.insert(id, span);
self.unused_import(self.base_id).add(id);
}
} else {
let base_id = self.base_id;
self.check_import(base_id, id, use_tree.span);
self.check_import(id);
}
visit::walk_use_tree(self, use_tree, id);
}
}
enum UnusedSpanResult {
Used,
FlatUnused(Span, Span),
NestedFullUnused(Vec<Span>, Span),
NestedPartialUnused(Vec<Span>, Vec<Span>),
}
fn calc_unused_spans(
unused_import: &UnusedImport<'_>,
use_tree: &ast::UseTree,
use_tree_id: ast::NodeId,
) -> UnusedSpanResult {
// The full span is the whole item's span if this current tree is not nested inside another
// This tells rustfix to remove the whole item if all the imports are unused
let full_span = if unused_import.use_tree.span == use_tree.span {
unused_import.item_span
} else {
use_tree.span
};
match use_tree.kind {
ast::UseTreeKind::Simple(..) | ast::UseTreeKind::Glob => {
if unused_import.unused.contains(&use_tree_id) {
UnusedSpanResult::FlatUnused(use_tree.span, full_span)
} else {
UnusedSpanResult::Used
}
}
ast::UseTreeKind::Nested(ref nested) => {
if nested.len() == 0 {
return UnusedSpanResult::FlatUnused(use_tree.span, full_span);
}
let mut unused_spans = Vec::new();
let mut to_remove = Vec::new();
let mut all_nested_unused = true;
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) {
UnusedSpanResult::Used => {
all_nested_unused = false;
None
}
UnusedSpanResult::FlatUnused(span, remove) => {
unused_spans.push(span);
Some(remove)
}
UnusedSpanResult::NestedFullUnused(mut spans, remove) => {
unused_spans.append(&mut spans);
Some(remove)
}
UnusedSpanResult::NestedPartialUnused(mut spans, mut to_remove_extra) => {
all_nested_unused = false;
unused_spans.append(&mut spans);
to_remove.append(&mut to_remove_extra);
None
}
};
if let Some(remove) = remove {
let remove_span = if nested.len() == 1 {
remove
} else if pos == nested.len() - 1 || !all_nested_unused {
// Delete everything from the end of the last import, to delete the
// previous comma
nested[pos - 1].0.span.shrink_to_hi().to(use_tree.span)
} else {
// Delete everything until the next import, to delete the trailing commas
use_tree.span.to(nested[pos + 1].0.span.shrink_to_lo())
};
// Try to collapse adjacent spans into a single one. This prevents all cases of
// overlapping removals, which are not supported by rustfix
if previous_unused && !to_remove.is_empty() {
let previous = to_remove.pop().unwrap();
to_remove.push(previous.to(remove_span));
} else {
to_remove.push(remove_span);
}
}
previous_unused = remove.is_some();
}
if unused_spans.is_empty() {
UnusedSpanResult::Used
} else if all_nested_unused {
UnusedSpanResult::NestedFullUnused(unused_spans, full_span)
} else {
UnusedSpanResult::NestedPartialUnused(unused_spans, to_remove)
}
}
}
}
pub fn check_crate(resolver: &mut Resolver<'_>, krate: &ast::Crate) {
for directive in resolver.potentially_unused_imports.iter() {
match directive.subclass {
@ -152,14 +277,33 @@ pub fn check_crate(resolver: &mut Resolver<'_>, krate: &ast::Crate) {
let mut visitor = UnusedImportCheckVisitor {
resolver,
unused_imports: Default::default(),
base_use_tree: None,
base_id: ast::DUMMY_NODE_ID,
item_span: DUMMY_SP,
};
visit::walk_crate(&mut visitor, krate);
for (id, spans) in &visitor.unused_imports {
for unused in visitor.unused_imports.values() {
let mut fixes = Vec::new();
let mut spans = match calc_unused_spans(unused, unused.use_tree, unused.use_tree_id) {
UnusedSpanResult::Used => continue,
UnusedSpanResult::FlatUnused(span, remove) => {
fixes.push((remove, String::new()));
vec![span]
}
UnusedSpanResult::NestedFullUnused(spans, remove) => {
fixes.push((remove, String::new()));
spans
}
UnusedSpanResult::NestedPartialUnused(spans, remove) => {
for fix in &remove {
fixes.push((*fix, String::new()));
}
spans
}
};
let len = spans.len();
let mut spans = spans.values().cloned().collect::<Vec<Span>>();
spans.sort();
let ms = MultiSpan::from_spans(spans.clone());
let mut span_snippets = spans.iter()
@ -177,6 +321,21 @@ pub fn check_crate(resolver: &mut Resolver<'_>, krate: &ast::Crate) {
} else {
String::new()
});
visitor.session.buffer_lint(lint::builtin::UNUSED_IMPORTS, *id, ms, &msg);
let fix_msg = if fixes.len() == 1 && fixes[0].0 == unused.item_span {
"remove the whole `use` item"
} else if spans.len() > 1 {
"remove the unused imports"
} else {
"remove the unused import"
};
visitor.session.buffer_lint_with_diagnostic(
lint::builtin::UNUSED_IMPORTS,
unused.use_tree_id,
ms,
&msg,
lint::builtin::BuiltinLintDiagnostics::UnusedImports(fix_msg.into(), fixes),
);
}
}

2
src/test/ui/bad/bad-lint-cap2.stderr
View File

@ -2,7 +2,7 @@ error: unused import: `std::option`
--> $DIR/bad-lint-cap2.rs:6:5
|
LL | use std::option; //~ ERROR
| ^^^^^^^^^^^
| ----^^^^^^^^^^^- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/bad-lint-cap2.rs:4:9

2
src/test/ui/bad/bad-lint-cap3.stderr
View File

@ -2,7 +2,7 @@ warning: unused import: `std::option`
--> $DIR/bad-lint-cap3.rs:7:5
|
LL | use std::option; //~ WARN
| ^^^^^^^^^^^
| ----^^^^^^^^^^^- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/bad-lint-cap3.rs:4:9

2
src/test/ui/imports/unused.stderr
View File

@ -2,7 +2,7 @@ error: unused import: `super::f`
--> $DIR/unused.rs:7:24
|
LL | pub(super) use super::f; //~ ERROR unused
| ^^^^^^^^
| ---------------^^^^^^^^- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/unused.rs:1:9

2
src/test/ui/issues/issue-30730.stderr
View File

@ -2,7 +2,7 @@ error: unused import: `std::thread`
--> $DIR/issue-30730.rs:3:5
|
LL | use std::thread;
| ^^^^^^^^^^^
| ----^^^^^^^^^^^- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/issue-30730.rs:2:9

4
src/test/ui/lint/lint-directives-on-use-items-issue-10534.stderr
View File

@ -2,7 +2,7 @@ error: unused import: `a::x`
--> $DIR/lint-directives-on-use-items-issue-10534.rs:12:9
|
LL | use a::x; //~ ERROR: unused import
| ^^^^
| ----^^^^- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/lint-directives-on-use-items-issue-10534.rs:1:9
@ -14,7 +14,7 @@ error: unused import: `a::y`
--> $DIR/lint-directives-on-use-items-issue-10534.rs:21:9
|
LL | use a::y; //~ ERROR: unused import
| ^^^^
| ----^^^^- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/lint-directives-on-use-items-issue-10534.rs:20:12

2
src/test/ui/lint/lint-unused-imports.rs
View File

@ -6,7 +6,7 @@ use bar::c::cc as cal;
use std::mem::*; // shouldn't get errors for not using
// everything imported
use std::fmt::{};
//~^ ERROR unused import: `use std::fmt::{};`
//~^ ERROR unused import: `std::fmt::{}`
// Should get errors for both 'Some' and 'None'
use std::option::Option::{Some, None};

20
src/test/ui/lint/lint-unused-imports.stderr
View File

@ -1,8 +1,8 @@
error: unused import: `use std::fmt::{};`
--> $DIR/lint-unused-imports.rs:8:1
error: unused import: `std::fmt::{}`
--> $DIR/lint-unused-imports.rs:8:5
|
LL | use std::fmt::{};
| ^^^^^^^^^^^^^^^^^
| ----^^^^^^^^^^^^- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/lint-unused-imports.rs:1:9
@ -14,37 +14,39 @@ error: unused imports: `None`, `Some`
--> $DIR/lint-unused-imports.rs:12:27
|
LL | use std::option::Option::{Some, None};
| ^^^^ ^^^^
| --------------------------^^^^--^^^^-- help: remove the whole `use` item
error: unused import: `test::A`
--> $DIR/lint-unused-imports.rs:15:5
|
LL | use test::A; //~ ERROR unused import: `test::A`
| ^^^^^^^
| ----^^^^^^^- help: remove the whole `use` item
error: unused import: `bar`
--> $DIR/lint-unused-imports.rs:24:18
|
LL | use test2::{foo, bar}; //~ ERROR unused import: `bar`
| ^^^
| --^^^
| |
| help: remove the unused import
error: unused import: `foo::Square`
--> $DIR/lint-unused-imports.rs:52:13
|
LL | use foo::Square; //~ ERROR unused import: `foo::Square`
| ^^^^^^^^^^^
| ----^^^^^^^^^^^- help: remove the whole `use` item
error: unused import: `self::g`
--> $DIR/lint-unused-imports.rs:68:9
|
LL | use self::g; //~ ERROR unused import: `self::g`
| ^^^^^^^
| ----^^^^^^^- help: remove the whole `use` item
error: unused import: `test2::foo`
--> $DIR/lint-unused-imports.rs:77:9
|
LL | use test2::foo; //~ ERROR unused import: `test2::foo`
| ^^^^^^^^^^
| ----^^^^^^^^^^- help: remove the whole `use` item
error: unused import: `test::B2`
--> $DIR/lint-unused-imports.rs:20:5

6
src/test/ui/lint/lints-in-foreign-macros.stderr
View File

@ -2,7 +2,7 @@ warning: unused import: `std::string::ToString`
--> $DIR/lints-in-foreign-macros.rs:11:16
|
LL | () => {use std::string::ToString;} //~ WARN: unused import
| ^^^^^^^^^^^^^^^^^^^^^
| ----^^^^^^^^^^^^^^^^^^^^^- help: remove the whole `use` item
...
LL | mod a { foo!(); }
| ------- in this macro invocation
@ -17,13 +17,13 @@ warning: unused import: `std::string::ToString`
--> $DIR/lints-in-foreign-macros.rs:16:18
|
LL | mod c { baz!(use std::string::ToString;); } //~ WARN: unused import
| ^^^^^^^^^^^^^^^^^^^^^
| ----^^^^^^^^^^^^^^^^^^^^^- help: remove the whole `use` item
warning: unused import: `std::string::ToString`
--> $DIR/lints-in-foreign-macros.rs:17:19
|
LL | mod d { baz2!(use std::string::ToString;); } //~ WARN: unused import
| ^^^^^^^^^^^^^^^^^^^^^
| ----^^^^^^^^^^^^^^^^^^^^^- help: remove the whole `use` item
warning: missing documentation for crate
--> $DIR/lints-in-foreign-macros.rs:4:1

4
src/test/ui/rfc-2166-underscore-imports/basic.stderr
View File

@ -2,7 +2,7 @@ warning: unused import: `m::Tr1 as _`
--> $DIR/basic.rs:26:9
|
LL | use m::Tr1 as _; //~ WARN unused import
| ^^^^^^^^^^^
| ----^^^^^^^^^^^- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/basic.rs:4:9
@ -14,5 +14,5 @@ warning: unused import: `S as _`
--> $DIR/basic.rs:27:9
|
LL | use S as _; //~ WARN unused import
| ^^^^^^
| ----^^^^^^- help: remove the whole `use` item

4
src/test/ui/rfc-2166-underscore-imports/unused-2018.stderr
View File

@ -2,7 +2,7 @@ error: unused import: `core::any`
--> $DIR/unused-2018.rs:6:9
|
LL | use core::any; //~ ERROR unused import: `core::any`
| ^^^^^^^^^
| ----^^^^^^^^^- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/unused-2018.rs:3:9
@ -14,7 +14,7 @@ error: unused import: `core`
--> $DIR/unused-2018.rs:10:9
|
LL | use core; //~ ERROR unused import: `core`
| ^^^^
| ----^^^^- help: remove the whole `use` item
error: aborting due to 2 previous errors

4
src/test/ui/span/multispan-import-lint.stderr
View File

@ -10,4 +10,8 @@ note: lint level defined here
LL | #![warn(unused)]
| ^^^^^^
= note: #[warn(unused_imports)] implied by #[warn(unused)]
help: remove the unused imports
|
LL | use std::cmp::{min};
| -- --

2
src/test/ui/use/use-nested-groups-unused-imports.rs
View File

@ -18,7 +18,7 @@ use foo::{Foo, bar::{baz::{}, foobar::*}, *};
use foo::bar::baz::{*, *};
//~^ ERROR unused import: `*`
use foo::{};
//~^ ERROR unused import: `use foo::{};`
//~^ ERROR unused import: `foo::{}`
fn main() {
let _: Bar;

12
src/test/ui/use/use-nested-groups-unused-imports.stderr
View File

@ -2,7 +2,7 @@ error: unused imports: `*`, `Foo`, `baz::{}`, `foobar::*`
--> $DIR/use-nested-groups-unused-imports.rs:16:11
|
LL | use foo::{Foo, bar::{baz::{}, foobar::*}, *};
| ^^^ ^^^^^^^ ^^^^^^^^^ ^
| ----------^^^--------^^^^^^^--^^^^^^^^^---^-- help: remove the whole `use` item
|
note: lint level defined here
--> $DIR/use-nested-groups-unused-imports.rs:3:9
@ -14,13 +14,15 @@ error: unused import: `*`
--> $DIR/use-nested-groups-unused-imports.rs:18:24
|
LL | use foo::bar::baz::{*, *};
| ^
| --^
| |
| help: remove the unused import
error: unused import: `use foo::{};`
--> $DIR/use-nested-groups-unused-imports.rs:20:1
error: unused import: `foo::{}`
--> $DIR/use-nested-groups-unused-imports.rs:20:5
|
LL | use foo::{};
| ^^^^^^^^^^^^
| ----^^^^^^^- help: remove the whole `use` item
error: aborting due to 3 previous errors