Merge #6016

6016: Emit diagnostics for unresolved imports and extern crates r=jonas-schievink a=jonas-schievink

AFAIK, we don't have any major bugs in name resolution that would cause a lot of false positives here (except procedural attribute macro support and some rare issues around `#[path]` on module files), so these are *not* marked as experimental diagnostics right now.

I noticed that diagnostics in a file sometimes don't get displayed after opening, but require some edit to be performed. This seems like a preexisting issue though.

Co-authored-by: Jonas Schievink <jonas.schievink@ferrous-systems.com>

crates/hir_def/src/diagnostics.rs

@@ -28,3 +28,45 @@ impl Diagnostic for UnresolvedModule {
         self
     }
 }
+
+#[derive(Debug)]
+pub struct UnresolvedExternCrate {
+    pub file: HirFileId,
+    pub item: AstPtr<ast::ExternCrate>,
+}
+
+impl Diagnostic for UnresolvedExternCrate {
+    fn code(&self) -> DiagnosticCode {
+        DiagnosticCode("unresolved-extern-crate")
+    }
+    fn message(&self) -> String {
+        "unresolved extern crate".to_string()
+    }
+    fn display_source(&self) -> InFile<SyntaxNodePtr> {
+        InFile::new(self.file, self.item.clone().into())
+    }
+    fn as_any(&self) -> &(dyn Any + Send + 'static) {
+        self
+    }
+}
+
+#[derive(Debug)]
+pub struct UnresolvedImport {
+    pub file: HirFileId,
+    pub node: AstPtr<ast::UseTree>,
+}
+
+impl Diagnostic for UnresolvedImport {
+    fn code(&self) -> DiagnosticCode {
+        DiagnosticCode("unresolved-import")
+    }
+    fn message(&self) -> String {
+        "unresolved import".to_string()
+    }
+    fn display_source(&self) -> InFile<SyntaxNodePtr> {
+        InFile::new(self.file, self.node.clone().into())
+    }
+    fn as_any(&self) -> &(dyn Any + Send + 'static) {
+        self
+    }
+}

crates/hir_def/src/item_tree.rs

@@ -291,7 +291,6 @@ pub enum AttrOwner {
 
     Variant(Idx<Variant>),
     Field(Idx<Field>),
-    // FIXME: Store variant and field attrs, and stop reparsing them in `attrs_query`.
 }
 
 macro_rules! from_attrs {
@@ -483,6 +482,11 @@ pub struct Import {
     /// AST ID of the `use` or `extern crate` item this import was derived from. Note that many
     /// `Import`s can map to the same `use` item.
     pub ast_id: FileAstId<ast::Use>,
+    /// Index of this `Import` when the containing `Use` is visited via `ModPath::expand_use_item`.
+    ///
+    /// This can be used to get the `UseTree` this `Import` corresponds to and allows emitting
+    /// precise diagnostics.
+    pub index: usize,
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]

crates/hir_def/src/item_tree/lower.rs

@@ -483,7 +483,7 @@ impl Ctx {
         ModPath::expand_use_item(
             InFile::new(self.file, use_item.clone()),
             &self.hygiene,
-            |path, _tree, is_glob, alias| {
+            |path, _use_tree, is_glob, alias| {
                 imports.push(id(tree.imports.alloc(Import {
                     path,
                     alias,
@@ -491,6 +491,7 @@ impl Ctx {
                     is_glob,
                     is_prelude,
                     ast_id,
+                    index: imports.len(),
                 })));
             },
         );

crates/hir_def/src/item_tree/tests.rs

@@ -228,9 +228,9 @@ fn smoke() {
 
             top-level items:
             #[Attrs { entries: Some([Attr { path: ModPath { kind: Plain, segments: [Name(Text("attr_on_use"))] }, input: None }]) }]
-            Import { path: ModPath { kind: Plain, segments: [Name(Text("a"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_glob: false, is_prelude: false, ast_id: FileAstId::<syntax::ast::generated::nodes::Use>(0) }
+            Import { path: ModPath { kind: Plain, segments: [Name(Text("a"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_glob: false, is_prelude: false, ast_id: FileAstId::<syntax::ast::generated::nodes::Use>(0), index: 0 }
             #[Attrs { entries: Some([Attr { path: ModPath { kind: Plain, segments: [Name(Text("attr_on_use"))] }, input: None }]) }]
-            Import { path: ModPath { kind: Plain, segments: [Name(Text("b"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_glob: true, is_prelude: false, ast_id: FileAstId::<syntax::ast::generated::nodes::Use>(0) }
+            Import { path: ModPath { kind: Plain, segments: [Name(Text("b"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_glob: true, is_prelude: false, ast_id: FileAstId::<syntax::ast::generated::nodes::Use>(0), index: 1 }
             #[Attrs { entries: Some([Attr { path: ModPath { kind: Plain, segments: [Name(Text("ext_crate"))] }, input: None }]) }]
             ExternCrate { path: ModPath { kind: Plain, segments: [Name(Text("krate"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_macro_use: false, ast_id: FileAstId::<syntax::ast::generated::nodes::ExternCrate>(1) }
             #[Attrs { entries: Some([Attr { path: ModPath { kind: Plain, segments: [Name(Text("on_trait"))] }, input: None }]) }]

crates/hir_def/src/nameres.rs

@@ -288,31 +288,70 @@ pub enum ModuleSource {
 
 mod diagnostics {
     use hir_expand::diagnostics::DiagnosticSink;
+    use hir_expand::hygiene::Hygiene;
+    use hir_expand::InFile;
     use syntax::{ast, AstPtr};
 
-    use crate::{db::DefDatabase, diagnostics::UnresolvedModule, nameres::LocalModuleId, AstId};
+    use crate::path::ModPath;
+    use crate::{db::DefDatabase, diagnostics::*, nameres::LocalModuleId, AstId};
 
     #[derive(Debug, PartialEq, Eq)]
-    pub(super) enum DefDiagnostic {
-        UnresolvedModule {
-            module: LocalModuleId,
-            declaration: AstId<ast::Module>,
-            candidate: String,
-        },
+    enum DiagnosticKind {
+        UnresolvedModule { declaration: AstId<ast::Module>, candidate: String },
+
+        UnresolvedExternCrate { ast: AstId<ast::ExternCrate> },
+
+        UnresolvedImport { ast: AstId<ast::Use>, index: usize },
+    }
+
+    #[derive(Debug, PartialEq, Eq)]
+    pub(super) struct DefDiagnostic {
+        in_module: LocalModuleId,
+        kind: DiagnosticKind,
     }
 
     impl DefDiagnostic {
+        pub(super) fn unresolved_module(
+            container: LocalModuleId,
+            declaration: AstId<ast::Module>,
+            candidate: String,
+        ) -> Self {
+            Self {
+                in_module: container,
+                kind: DiagnosticKind::UnresolvedModule { declaration, candidate },
+            }
+        }
+
+        pub(super) fn unresolved_extern_crate(
+            container: LocalModuleId,
+            declaration: AstId<ast::ExternCrate>,
+        ) -> Self {
+            Self {
+                in_module: container,
+                kind: DiagnosticKind::UnresolvedExternCrate { ast: declaration },
+            }
+        }
+
+        pub(super) fn unresolved_import(
+            container: LocalModuleId,
+            ast: AstId<ast::Use>,
+            index: usize,
+        ) -> Self {
+            Self { in_module: container, kind: DiagnosticKind::UnresolvedImport { ast, index } }
+        }
+
         pub(super) fn add_to(
             &self,
             db: &dyn DefDatabase,
             target_module: LocalModuleId,
             sink: &mut DiagnosticSink,
         ) {
-            match self {
-                DefDiagnostic::UnresolvedModule { module, declaration, candidate } => {
-                    if *module != target_module {
-                        return;
-                    }
+            if self.in_module != target_module {
+                return;
+            }
+
+            match &self.kind {
+                DiagnosticKind::UnresolvedModule { declaration, candidate } => {
                     let decl = declaration.to_node(db.upcast());
                     sink.push(UnresolvedModule {
                         file: declaration.file_id,
@@ -320,6 +359,36 @@ mod diagnostics {
                         candidate: candidate.clone(),
                     })
                 }
+
+                DiagnosticKind::UnresolvedExternCrate { ast } => {
+                    let item = ast.to_node(db.upcast());
+                    sink.push(UnresolvedExternCrate {
+                        file: ast.file_id,
+                        item: AstPtr::new(&item),
+                    });
+                }
+
+                DiagnosticKind::UnresolvedImport { ast, index } => {
+                    let use_item = ast.to_node(db.upcast());
+                    let hygiene = Hygiene::new(db.upcast(), ast.file_id);
+                    let mut cur = 0;
+                    let mut tree = None;
+                    ModPath::expand_use_item(
+                        InFile::new(ast.file_id, use_item),
+                        &hygiene,
+                        |_mod_path, use_tree, _is_glob, _alias| {
+                            if cur == *index {
+                                tree = Some(use_tree.clone());
+                            }
+
+                            cur += 1;
+                        },
+                    );
+
+                    if let Some(tree) = tree {
+                        sink.push(UnresolvedImport { file: ast.file_id, node: AstPtr::new(&tree) });
+                    }
+                }
             }
         }
     }

crates/hir_def/src/nameres/collector.rs

@@ -5,6 +5,7 @@
 
 use base_db::{CrateId, FileId, ProcMacroId};
 use cfg::CfgOptions;
+use hir_expand::InFile;
 use hir_expand::{
     ast_id_map::FileAstId,
     builtin_derive::find_builtin_derive,
@@ -14,6 +15,7 @@ use hir_expand::{
     HirFileId, MacroCallId, MacroDefId, MacroDefKind,
 };
 use rustc_hash::FxHashMap;
+use rustc_hash::FxHashSet;
 use syntax::ast;
 use test_utils::mark;
 
@@ -21,9 +23,7 @@ use crate::{
     attr::Attrs,
     db::DefDatabase,
     item_scope::{ImportType, PerNsGlobImports},
-    item_tree::{
-        self, FileItemTreeId, ItemTree, ItemTreeId, MacroCall, Mod, ModItem, ModKind, StructDefKind,
-    },
+    item_tree::{self, ItemTree, ItemTreeId, MacroCall, Mod, ModItem, ModKind, StructDefKind},
     nameres::{
         diagnostics::DefDiagnostic, mod_resolution::ModDir, path_resolution::ReachedFixedPoint,
         BuiltinShadowMode, CrateDefMap, ModuleData, ModuleOrigin, ResolveMode,
@@ -111,6 +111,12 @@ impl PartialResolvedImport {
     }
 }
 
+#[derive(Clone, Debug, Eq, PartialEq)]
+enum ImportSource {
+    Import(ItemTreeId<item_tree::Import>),
+    ExternCrate(ItemTreeId<item_tree::ExternCrate>),
+}
+
 #[derive(Clone, Debug, Eq, PartialEq)]
 struct Import {
     pub path: ModPath,
@@ -120,11 +126,12 @@ struct Import {
     pub is_prelude: bool,
     pub is_extern_crate: bool,
     pub is_macro_use: bool,
+    source: ImportSource,
 }
 
 impl Import {
-    fn from_use(tree: &ItemTree, id: FileItemTreeId<item_tree::Import>) -> Self {
-        let it = &tree[id];
+    fn from_use(tree: &ItemTree, id: ItemTreeId<item_tree::Import>) -> Self {
+        let it = &tree[id.value];
         let visibility = &tree[it.visibility];
         Self {
             path: it.path.clone(),
@@ -134,11 +141,12 @@ impl Import {
             is_prelude: it.is_prelude,
             is_extern_crate: false,
             is_macro_use: false,
+            source: ImportSource::Import(id),
         }
     }
 
-    fn from_extern_crate(tree: &ItemTree, id: FileItemTreeId<item_tree::ExternCrate>) -> Self {
-        let it = &tree[id];
+    fn from_extern_crate(tree: &ItemTree, id: ItemTreeId<item_tree::ExternCrate>) -> Self {
+        let it = &tree[id.value];
         let visibility = &tree[it.visibility];
         Self {
             path: it.path.clone(),
@@ -148,6 +156,7 @@ impl Import {
             is_prelude: false,
             is_extern_crate: true,
             is_macro_use: it.is_macro_use,
+            source: ImportSource::ExternCrate(id),
         }
     }
 }
@@ -245,9 +254,10 @@ impl DefCollector<'_> {
 
         let unresolved_imports = std::mem::replace(&mut self.unresolved_imports, Vec::new());
         // show unresolved imports in completion, etc
-        for directive in unresolved_imports {
-            self.record_resolved_import(&directive)
+        for directive in &unresolved_imports {
+            self.record_resolved_import(directive)
         }
+        self.unresolved_imports = unresolved_imports;
 
         // Record proc-macros
         self.collect_proc_macro();
@@ -420,7 +430,11 @@ impl DefCollector<'_> {
                     .as_ident()
                     .expect("extern crate should have been desugared to one-element path"),
             );
-            PartialResolvedImport::Resolved(res)
+            if res.is_none() {
+                PartialResolvedImport::Unresolved
+            } else {
+                PartialResolvedImport::Resolved(res)
+            }
         } else {
             let res = self.def_map.resolve_path_fp_with_macro(
                 self.db,
@@ -774,7 +788,51 @@ impl DefCollector<'_> {
         .collect(item_tree.top_level_items());
     }
 
-    fn finish(self) -> CrateDefMap {
+    fn finish(mut self) -> CrateDefMap {
+        // Emit diagnostics for all remaining unresolved imports.
+
+        // We'd like to avoid emitting a diagnostics avalanche when some `extern crate` doesn't
+        // resolve. We first emit diagnostics for unresolved extern crates and collect the missing
+        // crate names. Then we emit diagnostics for unresolved imports, but only if the import
+        // doesn't start with an unresolved crate's name. Due to renaming and reexports, this is a
+        // heuristic, but it works in practice.
+        let mut diagnosed_extern_crates = FxHashSet::default();
+        for directive in &self.unresolved_imports {
+            if let ImportSource::ExternCrate(krate) = directive.import.source {
+                let item_tree = self.db.item_tree(krate.file_id);
+                let extern_crate = &item_tree[krate.value];
+
+                diagnosed_extern_crates.insert(extern_crate.path.segments[0].clone());
+
+                self.def_map.diagnostics.push(DefDiagnostic::unresolved_extern_crate(
+                    directive.module_id,
+                    InFile::new(krate.file_id, extern_crate.ast_id),
+                ));
+            }
+        }
+
+        for directive in &self.unresolved_imports {
+            if let ImportSource::Import(import) = &directive.import.source {
+                let item_tree = self.db.item_tree(import.file_id);
+                let import_data = &item_tree[import.value];
+
+                match (import_data.path.segments.first(), &import_data.path.kind) {
+                    (Some(krate), PathKind::Plain) | (Some(krate), PathKind::Abs) => {
+                        if diagnosed_extern_crates.contains(krate) {
+                            continue;
+                        }
+                    }
+                    _ => {}
+                }
+
+                self.def_map.diagnostics.push(DefDiagnostic::unresolved_import(
+                    directive.module_id,
+                    InFile::new(import.file_id, import_data.ast_id),
+                    import_data.index,
+                ));
+            }
+        }
+
         self.def_map
     }
 }
@@ -830,14 +888,20 @@ impl ModCollector<'_, '_> {
                     ModItem::Import(import_id) => {
                         self.def_collector.unresolved_imports.push(ImportDirective {
                             module_id: self.module_id,
-                            import: Import::from_use(&self.item_tree, import_id),
+                            import: Import::from_use(
+                                &self.item_tree,
+                                InFile::new(self.file_id, import_id),
+                            ),
                             status: PartialResolvedImport::Unresolved,
                         })
                     }
                     ModItem::ExternCrate(import_id) => {
                         self.def_collector.unresolved_imports.push(ImportDirective {
                             module_id: self.module_id,
-                            import: Import::from_extern_crate(&self.item_tree, import_id),
+                            import: Import::from_extern_crate(
+                                &self.item_tree,
+                                InFile::new(self.file_id, import_id),
+                            ),
                             status: PartialResolvedImport::Unresolved,
                         })
                     }
@@ -1051,13 +1115,11 @@ impl ModCollector<'_, '_> {
                             self.import_all_legacy_macros(module_id);
                         }
                     }
-                    Err(candidate) => self.def_collector.def_map.diagnostics.push(
-                        DefDiagnostic::UnresolvedModule {
-                            module: self.module_id,
-                            declaration: ast_id,
-                            candidate,
-                        },
-                    ),
+                    Err(candidate) => {
+                        self.def_collector.def_map.diagnostics.push(
+                            DefDiagnostic::unresolved_module(self.module_id, ast_id, candidate),
+                        );
+                    }
                 };
             }
         }

crates/hir_def/src/nameres/tests.rs

@@ -2,6 +2,7 @@ mod globs;
 mod incremental;
 mod macros;
 mod mod_resolution;
+mod diagnostics;
 mod primitives;
 
 use std::sync::Arc;

crates/hir_def/src/nameres/tests/diagnostics.rs

@@ -0,0 +1,131 @@
+use base_db::fixture::WithFixture;
+use base_db::FileId;
+use base_db::SourceDatabaseExt;
+use hir_expand::db::AstDatabase;
+use rustc_hash::FxHashMap;
+use syntax::TextRange;
+use syntax::TextSize;
+
+use crate::test_db::TestDB;
+
+fn check_diagnostics(ra_fixture: &str) {
+    let db: TestDB = TestDB::with_files(ra_fixture);
+    let annotations = db.extract_annotations();
+    assert!(!annotations.is_empty());
+
+    let mut actual: FxHashMap<FileId, Vec<(TextRange, String)>> = FxHashMap::default();
+    db.diagnostics(|d| {
+        let src = d.display_source();
+        let root = db.parse_or_expand(src.file_id).unwrap();
+        // FIXME: macros...
+        let file_id = src.file_id.original_file(&db);
+        let range = src.value.to_node(&root).text_range();
+        let message = d.message().to_owned();
+        actual.entry(file_id).or_default().push((range, message));
+    });
+
+    for (file_id, diags) in actual.iter_mut() {
+        diags.sort_by_key(|it| it.0.start());
+        let text = db.file_text(*file_id);
+        // For multiline spans, place them on line start
+        for (range, content) in diags {
+            if text[*range].contains('\n') {
+                *range = TextRange::new(range.start(), range.start() + TextSize::from(1));
+                *content = format!("... {}", content);
+            }
+        }
+    }
+
+    assert_eq!(annotations, actual);
+}
+
+#[test]
+fn unresolved_import() {
+    check_diagnostics(
+        r"
+        use does_exist;
+        use does_not_exist;
+          //^^^^^^^^^^^^^^ unresolved import
+
+        mod does_exist {}
+        ",
+    );
+}
+
+#[test]
+fn unresolved_import_in_use_tree() {
+    // Only the relevant part of a nested `use` item should be highlighted.
+    check_diagnostics(
+        r"
+        use does_exist::{Exists, DoesntExist};
+                               //^^^^^^^^^^^ unresolved import
+
+        use {does_not_exist::*, does_exist};
+           //^^^^^^^^^^^^^^^^^ unresolved import
+
+        use does_not_exist::{
+            a,
+          //^ unresolved import
+            b,
+          //^ unresolved import
+            c,
+          //^ unresolved import
+        };
+
+        mod does_exist {
+            pub struct Exists;
+        }
+        ",
+    );
+}
+
+#[test]
+fn unresolved_extern_crate() {
+    check_diagnostics(
+        r"
+        //- /main.rs crate:main deps:core
+        extern crate core;
+          extern crate doesnotexist;
+        //^^^^^^^^^^^^^^^^^^^^^^^^^^ unresolved extern crate
+        //- /lib.rs crate:core
+        ",
+    );
+}
+
+#[test]
+fn dedup_unresolved_import_from_unresolved_crate() {
+    check_diagnostics(
+        r"
+        //- /main.rs crate:main
+        mod a {
+            extern crate doesnotexist;
+          //^^^^^^^^^^^^^^^^^^^^^^^^^^ unresolved extern crate
+
+            // Should not error, since we already errored for the missing crate.
+            use doesnotexist::{self, bla, *};
+
+            use crate::doesnotexist;
+              //^^^^^^^^^^^^^^^^^^^ unresolved import
+        }
+
+        mod m {
+            use super::doesnotexist;
+              //^^^^^^^^^^^^^^^^^^^ unresolved import
+        }
+        ",
+    );
+}
+
+#[test]
+fn unresolved_module() {
+    check_diagnostics(
+        r"
+        //- /lib.rs
+        mod foo;
+          mod bar;
+        //^^^^^^^^ unresolved module
+        mod baz {}
+        //- /foo.rs
+        ",
+    );
+}

crates/hir_def/src/nameres/tests/mod_resolution.rs

@@ -671,42 +671,6 @@ pub struct Baz;
     );
 }
 
-#[test]
-fn unresolved_module_diagnostics() {
-    let db = TestDB::with_files(
-        r"
-        //- /lib.rs
-        mod foo;
-        mod bar;
-        mod baz {}
-        //- /foo.rs
-        ",
-    );
-    let krate = db.test_crate();
-
-    let crate_def_map = db.crate_def_map(krate);
-
-    expect![[r#"
-        [
-            UnresolvedModule {
-                module: Idx::<ModuleData>(0),
-                declaration: InFile {
-                    file_id: HirFileId(
-                        FileId(
-                            FileId(
-                                0,
-                            ),
-                        ),
-                    ),
-                    value: FileAstId::<syntax::ast::generated::nodes::Module>(1),
-                },
-                candidate: "bar.rs",
-            },
-        ]
-    "#]]
-    .assert_debug_eq(&crate_def_map.diagnostics);
-}
-
 #[test]
 fn module_resolution_decl_inside_module_in_non_crate_root_2() {
     check(

crates/hir_def/src/test_db.rs

@@ -5,9 +5,15 @@ use std::{
     sync::{Arc, Mutex},
 };
 
+use base_db::SourceDatabase;
 use base_db::{salsa, CrateId, FileId, FileLoader, FileLoaderDelegate, Upcast};
 use hir_expand::db::AstDatabase;
+use hir_expand::diagnostics::Diagnostic;
+use hir_expand::diagnostics::DiagnosticSinkBuilder;
+use rustc_hash::FxHashMap;
 use rustc_hash::FxHashSet;
+use syntax::TextRange;
+use test_utils::extract_annotations;
 
 use crate::db::DefDatabase;
 
@@ -98,4 +104,40 @@ impl TestDB {
             })
             .collect()
     }
+
+    pub fn extract_annotations(&self) -> FxHashMap<FileId, Vec<(TextRange, String)>> {
+        let mut files = Vec::new();
+        let crate_graph = self.crate_graph();
+        for krate in crate_graph.iter() {
+            let crate_def_map = self.crate_def_map(krate);
+            for (module_id, _) in crate_def_map.modules.iter() {
+                let file_id = crate_def_map[module_id].origin.file_id();
+                files.extend(file_id)
+            }
+        }
+        assert!(!files.is_empty());
+        files
+            .into_iter()
+            .filter_map(|file_id| {
+                let text = self.file_text(file_id);
+                let annotations = extract_annotations(&text);
+                if annotations.is_empty() {
+                    return None;
+                }
+                Some((file_id, annotations))
+            })
+            .collect()
+    }
+
+    pub fn diagnostics<F: FnMut(&dyn Diagnostic)>(&self, mut cb: F) {
+        let crate_graph = self.crate_graph();
+        for krate in crate_graph.iter() {
+            let crate_def_map = self.crate_def_map(krate);
+
+            let mut sink = DiagnosticSinkBuilder::new().build(&mut cb);
+            for (module_id, _) in crate_def_map.modules.iter() {
+                crate_def_map.add_diagnostics(self, module_id, &mut sink);
+            }
+        }
+    }
 }

crates/ide/src/diagnostics.rs

@@ -622,13 +622,65 @@ pub struct Foo { pub a: i32, pub b: i32 }
             r#"
 use a;
 use a::{c, d::e};
+
+mod a {
+    mod c {}
+    mod d {
+        mod e {}
+    }
+}
 "#,
         );
-        check_fix(r#"use {<|>b};"#, r#"use b;"#);
-        check_fix(r#"use {b<|>};"#, r#"use b;"#);
-        check_fix(r#"use a::{c<|>};"#, r#"use a::c;"#);
-        check_fix(r#"use a::{self<|>};"#, r#"use a;"#);
-        check_fix(r#"use a::{c, d::{e<|>}};"#, r#"use a::{c, d::e};"#);
+        check_fix(
+            r"
+            mod b {}
+            use {<|>b};
+            ",
+            r"
+            mod b {}
+            use b;
+            ",
+        );
+        check_fix(
+            r"
+            mod b {}
+            use {b<|>};
+            ",
+            r"
+            mod b {}
+            use b;
+            ",
+        );
+        check_fix(
+            r"
+            mod a { mod c {} }
+            use a::{c<|>};
+            ",
+            r"
+            mod a { mod c {} }
+            use a::c;
+            ",
+        );
+        check_fix(
+            r"
+            mod a {}
+            use a::{self<|>};
+            ",
+            r"
+            mod a {}
+            use a;
+            ",
+        );
+        check_fix(
+            r"
+            mod a { mod c {} mod d { mod e {} } }
+            use a::{c, d::{e<|>}};
+            ",
+            r"
+            mod a { mod c {} mod d { mod e {} } }
+            use a::{c, d::e};
+            ",
+        );
     }
 
     #[test]