By tracking import use types to check whether it is scope uses or the other situations like module-relative uses, we can do more accurate redundant import checking.

fixes #117448

For example unnecessary imports in std::prelude that can be eliminated:

```rust
use std::option::Option::Some;//~ WARNING the item `Some` is imported redundantly
use std::option::Option::None; //~ WARNING the item `None` is imported redundantly
```

compiler/rustc_data_structures/src/owned_slice.rs

@@ -4,7 +4,7 @@ use crate::sync::Lrc;
 // Use our fake Send/Sync traits when on not parallel compiler,
 // so that `OwnedSlice` only implements/requires Send/Sync
 // for parallel compiler builds.
-use crate::sync::{Send, Sync};
+use crate::sync;
 
 /// An owned slice.
 ///
@@ -33,7 +33,7 @@ pub struct OwnedSlice {
     //       \/
     //      ⊂(´･◡･⊂ )∘˚˳° (I am the phantom remnant of #97770)
     #[expect(dead_code)]
-    owner: Lrc<dyn Send + Sync>,
+    owner: Lrc<dyn sync::Send + sync::Sync>,
 }
 
 /// Makes an [`OwnedSlice`] out of an `owner` and a `slicer` function.
@@ -60,7 +60,7 @@ pub struct OwnedSlice {
 /// ```
 pub fn slice_owned<O, F>(owner: O, slicer: F) -> OwnedSlice
 where
-    O: Send + Sync + 'static,
+    O: sync::Send + sync::Sync + 'static,
     F: FnOnce(&O) -> &[u8],
 {
     try_slice_owned(owner, |x| Ok::<_, !>(slicer(x))).into_ok()
@@ -71,7 +71,7 @@ where
 /// See [`slice_owned`] for the infallible version.
 pub fn try_slice_owned<O, F, E>(owner: O, slicer: F) -> Result<OwnedSlice, E>
 where
-    O: Send + Sync + 'static,
+    O: sync::Send + sync::Sync + 'static,
     F: FnOnce(&O) -> Result<&[u8], E>,
 {
     // We wrap the owner of the bytes in, so it doesn't move.
@@ -139,11 +139,11 @@ impl Borrow<[u8]> for OwnedSlice {
 
 // Safety: `OwnedSlice` is conceptually `(&'self.1 [u8], Arc<dyn Send + Sync>)`, which is `Send`
 #[cfg(parallel_compiler)]
-unsafe impl Send for OwnedSlice {}
+unsafe impl sync::Send for OwnedSlice {}
 
 // Safety: `OwnedSlice` is conceptually `(&'self.1 [u8], Arc<dyn Send + Sync>)`, which is `Sync`
 #[cfg(parallel_compiler)]
-unsafe impl Sync for OwnedSlice {}
+unsafe impl sync::Sync for OwnedSlice {}
 
 #[cfg(test)]
 mod tests;

compiler/rustc_hir_analysis/src/check/check.rs

@@ -5,10 +5,9 @@ use super::compare_impl_item::check_type_bounds;
 use super::compare_impl_item::{compare_impl_method, compare_impl_ty};
 use super::*;
 use rustc_attr as attr;
-use rustc_errors::{codes::*, ErrorGuaranteed, MultiSpan};
+use rustc_errors::{codes::*, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind};
-use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::Node;
 use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
 use rustc_infer::traits::{Obligation, TraitEngineExt as _};

compiler/rustc_hir_analysis/src/structured_errors/missing_cast_for_variadic_arg.rs

@@ -1,5 +1,5 @@
 use crate::{errors, structured_errors::StructuredDiagnostic};
-use rustc_errors::{codes::*, DiagnosticBuilder, ErrCode};
+use rustc_errors::{codes::*, DiagnosticBuilder};
 use rustc_middle::ty::{Ty, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_span::Span;

compiler/rustc_hir_analysis/src/structured_errors/sized_unsized_cast.rs

@@ -1,5 +1,5 @@
 use crate::{errors, structured_errors::StructuredDiagnostic};
-use rustc_errors::{codes::*, DiagnosticBuilder, ErrCode};
+use rustc_errors::{codes::*, DiagnosticBuilder};
 use rustc_middle::ty::{Ty, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_span::Span;

compiler/rustc_hir_analysis/src/structured_errors/wrong_number_of_generic_args.rs

@@ -1,7 +1,5 @@
 use crate::structured_errors::StructuredDiagnostic;
-use rustc_errors::{
+use rustc_errors::{codes::*, pluralize, Applicability, Diagnostic, DiagnosticBuilder, MultiSpan};
-    codes::*, pluralize, Applicability, Diagnostic, DiagnosticBuilder, ErrCode, MultiSpan,
-};
 use rustc_hir as hir;
 use rustc_middle::ty::{self as ty, AssocItems, AssocKind, TyCtxt};
 use rustc_session::Session;

compiler/rustc_hir_typeck/src/expr.rs

@@ -27,7 +27,7 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{
     codes::*, pluralize, struct_span_code_err, AddToDiagnostic, Applicability, Diagnostic,
-    DiagnosticBuilder, ErrCode, ErrorGuaranteed, StashKey,
+    DiagnosticBuilder, ErrorGuaranteed, StashKey,
 };
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind, Res};

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -13,7 +13,7 @@ use itertools::Itertools;
 use rustc_ast as ast;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{
-    codes::*, pluralize, Applicability, Diagnostic, ErrCode, ErrorGuaranteed, MultiSpan, StashKey,
+    codes::*, pluralize, Applicability, Diagnostic, ErrorGuaranteed, MultiSpan, StashKey,
 };
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind, Res};

compiler/rustc_hir_typeck/src/lib.rs

@@ -53,7 +53,7 @@ use crate::expectation::Expectation;
 use crate::fn_ctxt::LoweredTy;
 use crate::gather_locals::GatherLocalsVisitor;
 use rustc_data_structures::unord::UnordSet;
-use rustc_errors::{codes::*, struct_span_code_err, ErrCode, ErrorGuaranteed};
+use rustc_errors::{codes::*, struct_span_code_err, ErrorGuaranteed};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::Visitor;

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -5,7 +5,7 @@ use crate::errors::{
 use crate::infer::error_reporting::TypeErrCtxt;
 use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use crate::infer::InferCtxt;
-use rustc_errors::{codes::*, DiagnosticBuilder, ErrCode, IntoDiagnosticArg};
+use rustc_errors::{codes::*, DiagnosticBuilder, IntoDiagnosticArg};
 use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::def::{CtorOf, DefKind, Namespace};

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -13,7 +13,7 @@ use rustc_data_structures::unhash::UnhashMap;
 use rustc_expand::base::{SyntaxExtension, SyntaxExtensionKind};
 use rustc_expand::proc_macro::{AttrProcMacro, BangProcMacro, DeriveProcMacro};
 use rustc_hir::def::Res;
-use rustc_hir::def_id::{DefIdMap, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::definitions::{DefPath, DefPathData};
 use rustc_hir::diagnostic_items::DiagnosticItems;
 use rustc_index::Idx;

compiler/rustc_middle/src/mir/syntax.rs

@@ -15,7 +15,7 @@ use crate::ty::{Region, UserTypeAnnotationIndex};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_data_structures::packed::Pu128;
 use rustc_hir::def_id::DefId;
-use rustc_hir::{self, CoroutineKind};
+use rustc_hir::CoroutineKind;
 use rustc_index::IndexVec;
 use rustc_span::source_map::Spanned;
 use rustc_target::abi::{FieldIdx, VariantIdx};

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -8,11 +8,11 @@
 use crate::def_collector::collect_definitions;
 use crate::imports::{ImportData, ImportKind};
 use crate::macros::{MacroRulesBinding, MacroRulesScope, MacroRulesScopeRef};
-use crate::Namespace::{self, MacroNS, TypeNS, ValueNS};
+use crate::Namespace::{MacroNS, TypeNS, ValueNS};
 use crate::{errors, BindingKey, MacroData, NameBindingData};
 use crate::{Determinacy, ExternPreludeEntry, Finalize, Module, ModuleKind, ModuleOrUniformRoot};
-use crate::{NameBinding, NameBindingKind, ParentScope, PathResult, PerNS, ResolutionError};
+use crate::{NameBinding, NameBindingKind, ParentScope, PathResult, ResolutionError};
-use crate::{Resolver, ResolverArenas, Segment, ToNameBinding, VisResolutionError};
+use crate::{Resolver, ResolverArenas, Segment, ToNameBinding, Used, VisResolutionError};
 
 use rustc_ast::visit::{self, AssocCtxt, Visitor};
 use rustc_ast::{self as ast, AssocItem, AssocItemKind, MetaItemKind, StmtKind};
@@ -362,7 +362,7 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
             root_span,
             root_id,
             vis: Cell::new(Some(vis)),
-            used: Cell::new(false),
+            used: Default::default(),
         });
 
         self.r.indeterminate_imports.push(import);
@@ -885,7 +885,7 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
             span: item.span,
             module_path: Vec::new(),
             vis: Cell::new(Some(vis)),
-            used: Cell::new(used),
+            used: Cell::new(used.then_some(Used::Other)),
         });
         self.r.potentially_unused_imports.push(import);
         let imported_binding = self.r.import(binding, import);
@@ -1090,7 +1090,7 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
                 span,
                 module_path: Vec::new(),
                 vis: Cell::new(Some(ty::Visibility::Restricted(CRATE_DEF_ID))),
-                used: Cell::new(false),
+                used: Default::default(),
             })
         };
 
@@ -1261,7 +1261,7 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
                     span,
                     module_path: Vec::new(),
                     vis: Cell::new(Some(vis)),
-                    used: Cell::new(true),
+                    used: Cell::new(Some(Used::Other)),
                 });
                 let import_binding = self.r.import(binding, import);
                 self.r.define(self.r.graph_root, ident, MacroNS, import_binding);

compiler/rustc_resolve/src/check_unused.rs

@@ -27,9 +27,10 @@ use crate::imports::ImportKind;
 use crate::module_to_string;
 use crate::Resolver;
 
+use crate::NameBindingKind;
 use rustc_ast as ast;
 use rustc_ast::visit::{self, Visitor};
-use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
+use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::{pluralize, MultiSpan};
 use rustc_hir::def::{DefKind, Res};
@@ -38,14 +39,14 @@ use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_span::symbol::{kw, Ident};
 use rustc_span::{Span, DUMMY_SP};
 
-struct UnusedImport<'a> {
+struct UnusedImport {
-    use_tree: &'a ast::UseTree,
+    use_tree: ast::UseTree,
     use_tree_id: ast::NodeId,
     item_span: Span,
     unused: UnordSet<ast::NodeId>,
 }
 
-impl<'a> UnusedImport<'a> {
+impl UnusedImport {
     fn add(&mut self, id: ast::NodeId) {
         self.unused.insert(id);
     }
@@ -54,7 +55,7 @@ impl<'a> UnusedImport<'a> {
 struct UnusedImportCheckVisitor<'a, 'b, 'tcx> {
     r: &'a mut Resolver<'b, 'tcx>,
     /// All the (so far) unused imports, grouped path list
-    unused_imports: FxIndexMap<ast::NodeId, UnusedImport<'a>>,
+    unused_imports: FxIndexMap<ast::NodeId, UnusedImport>,
     extern_crate_items: Vec<ExternCrateToLint>,
     base_use_tree: Option<&'a ast::UseTree>,
     base_id: ast::NodeId,
@@ -100,9 +101,9 @@ impl<'a, 'b, 'tcx> UnusedImportCheckVisitor<'a, 'b, 'tcx> {
         }
     }
 
-    fn unused_import(&mut self, id: ast::NodeId) -> &mut UnusedImport<'a> {
+    fn unused_import(&mut self, id: ast::NodeId) -> &mut UnusedImport {
         let use_tree_id = self.base_id;
-        let use_tree = self.base_use_tree.unwrap();
+        let use_tree = self.base_use_tree.unwrap().clone();
         let item_span = self.item_span;
 
         self.unused_imports.entry(id).or_insert_with(|| UnusedImport {
@@ -197,7 +198,7 @@ enum UnusedSpanResult {
 }
 
 fn calc_unused_spans(
-    unused_import: &UnusedImport<'_>,
+    unused_import: &UnusedImport,
     use_tree: &ast::UseTree,
     use_tree_id: ast::NodeId,
 ) -> UnusedSpanResult {
@@ -287,7 +288,7 @@ impl Resolver<'_, '_> {
 
         for import in self.potentially_unused_imports.iter() {
             match import.kind {
-                _ if import.used.get()
+                _ if import.used.get().is_some()
                     || import.expect_vis().is_public()
                     || import.span.is_dummy() =>
                 {
@@ -336,7 +337,7 @@ impl Resolver<'_, '_> {
 
         for unused in visitor.unused_imports.values() {
             let mut fixes = Vec::new();
-            let spans = match calc_unused_spans(unused, unused.use_tree, unused.use_tree_id) {
+            let 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()));
@@ -483,5 +484,30 @@ impl Resolver<'_, '_> {
                 BuiltinLintDiagnostics::ExternCrateNotIdiomatic { vis_span, ident_span },
             );
         }
+
+        let unused_imports = visitor.unused_imports;
+        let mut check_redundant_imports = FxIndexSet::default();
+        for module in self.arenas.local_modules().iter() {
+            for (_key, resolution) in self.resolutions(*module).borrow().iter() {
+                let resolution = resolution.borrow();
+
+                if let Some(binding) = resolution.binding
+                    && let NameBindingKind::Import { import, .. } = binding.kind
+                    && let ImportKind::Single { id, .. } = import.kind
+                {
+                    if let Some(unused_import) = unused_imports.get(&import.root_id)
+                        && unused_import.unused.contains(&id)
+                    {
+                        continue;
+                    }
+
+                    check_redundant_imports.insert(import);
+                }
+            }
+        }
+
+        for import in check_redundant_imports {
+            self.check_for_redundant_imports(import);
+        }
     }
 }

compiler/rustc_resolve/src/def_collector.rs

@@ -1,5 +1,5 @@
 use crate::{ImplTraitContext, Resolver};
-use rustc_ast::visit::{self, FnKind};
+use rustc_ast::visit::FnKind;
 use rustc_ast::*;
 use rustc_expand::expand::AstFragment;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind};

compiler/rustc_resolve/src/diagnostics.rs

@@ -33,8 +33,8 @@ use crate::errors::{AddedMacroUse, ChangeImportBinding, ChangeImportBindingSugge
 use crate::errors::{ConsiderAddingADerive, ExplicitUnsafeTraits, MaybeMissingMacroRulesName};
 use crate::imports::{Import, ImportKind};
 use crate::late::{PatternSource, Rib};
-use crate::path_names_to_string;
 use crate::{errors as errs, BindingKey};
+use crate::{path_names_to_string, Used};
 use crate::{AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, BindingError, Finalize};
 use crate::{HasGenericParams, MacroRulesScope, Module, ModuleKind, ModuleOrUniformRoot};
 use crate::{LexicalScopeBinding, NameBinding, NameBindingKind, PrivacyError, VisResolutionError};
@@ -1503,7 +1503,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                         );
                         // Silence the 'unused import' warning we might get,
                         // since this diagnostic already covers that import.
-                        self.record_use(ident, binding, false);
+                        self.record_use(ident, binding, Used::Other);
                         return;
                     }
                 }

compiler/rustc_resolve/src/ident.rs

@@ -12,8 +12,8 @@ use rustc_span::Span;
 use crate::errors::{ParamKindInEnumDiscriminant, ParamKindInNonTrivialAnonConst};
 use crate::late::{ConstantHasGenerics, NoConstantGenericsReason, PathSource, Rib, RibKind};
 use crate::macros::{sub_namespace_match, MacroRulesScope};
-use crate::BindingKey;
 use crate::{errors, AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, Determinacy, Finalize};
+use crate::{BindingKey, Used};
 use crate::{ImportKind, LexicalScopeBinding, Module, ModuleKind, ModuleOrUniformRoot};
 use crate::{NameBinding, NameBindingKind, ParentScope, PathResult, PrivacyError, Res};
 use crate::{ResolutionError, Resolver, Scope, ScopeSet, Segment, ToNameBinding, Weak};
@@ -339,7 +339,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 ident,
                 ns,
                 parent_scope,
-                finalize,
+                finalize.map(|finalize| Finalize { used: Used::Scope, ..finalize }),
                 ignore_binding,
             );
             if let Ok(binding) = item {
@@ -506,7 +506,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                             ns,
                             adjusted_parent_scope,
                             !matches!(scope_set, ScopeSet::Late(..)),
-                            finalize,
+                            finalize.map(|finalize| Finalize { used: Used::Scope, ..finalize }),
                             ignore_binding,
                         );
                         match binding {
@@ -857,7 +857,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             .into_iter()
             .find_map(|binding| if binding == ignore_binding { None } else { binding });
 
-        if let Some(Finalize { path_span, report_private, .. }) = finalize {
+        if let Some(Finalize { path_span, report_private, used, .. }) = finalize {
             let Some(binding) = binding else {
                 return Err((Determined, Weak::No));
             };
@@ -901,7 +901,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 }
             }
 
-            self.record_use(ident, binding, restricted_shadowing);
+            self.record_use(ident, binding, used);
             return Ok(binding);
         }
 

compiler/rustc_resolve/src/imports.rs

@@ -10,9 +10,9 @@ use crate::errors::{
 use crate::Determinacy::{self, *};
 use crate::Namespace::*;
 use crate::{module_to_string, names_to_string, ImportSuggestion};
-use crate::{AmbiguityKind, BindingKey, ModuleKind, ResolutionError, Resolver, Segment};
+use crate::{AmbiguityKind, BindingKey, ResolutionError, Resolver, Segment};
 use crate::{Finalize, Module, ModuleOrUniformRoot, ParentScope, PerNS, ScopeSet};
-use crate::{NameBinding, NameBindingData, NameBindingKind, PathResult};
+use crate::{NameBinding, NameBindingData, NameBindingKind, PathResult, Used};
 
 use rustc_ast::NodeId;
 use rustc_data_structures::fx::FxHashSet;
@@ -173,7 +173,7 @@ pub(crate) struct ImportData<'a> {
     /// The resolution of `module_path`.
     pub imported_module: Cell<Option<ModuleOrUniformRoot<'a>>>,
     pub vis: Cell<Option<ty::Visibility>>,
-    pub used: Cell<bool>,
+    pub used: Cell<Option<Used>>,
 }
 
 /// All imports are unique and allocated on a same arena,
@@ -286,7 +286,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         }
 
         self.arenas.alloc_name_binding(NameBindingData {
-            kind: NameBindingKind::Import { binding, import, used: Cell::new(false) },
+            kind: NameBindingKind::Import { binding, import },
             ambiguity: None,
             warn_ambiguity: false,
             span: import.span,
@@ -485,9 +485,9 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     resolution.single_imports.remove(&import);
                 })
             });
-            self.record_use(target, dummy_binding, false);
+            self.record_use(target, dummy_binding, Used::Other);
         } else if import.imported_module.get().is_none() {
-            import.used.set(true);
+            import.used.set(Some(Used::Other));
             if let Some(id) = import.id() {
                 self.used_imports.insert(id);
             }
@@ -1056,11 +1056,12 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                                     && initial_binding.is_extern_crate()
                                     && !initial_binding.is_import()
                                 {
-                                    this.record_use(
+                                    let used = if import.module_path.is_empty() {
-                                        ident,
+                                        Used::Scope
-                                        target_binding,
+                                    } else {
-                                        import.module_path.is_empty(),
+                                        Used::Other
-                                    );
+                                    };
+                                    this.record_use(ident, target_binding, used);
                                 }
                             }
                             initial_binding.res()
@@ -1299,22 +1300,23 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             }
         });
 
-        self.check_for_redundant_imports(ident, import, source_bindings, target_bindings, target);
-
         debug!("(resolving single import) successfully resolved import");
         None
     }
 
-    fn check_for_redundant_imports(
+    pub(crate) fn check_for_redundant_imports(&mut self, import: Import<'a>) {
-        &mut self,
-        ident: Ident,
-        import: Import<'a>,
-        source_bindings: &PerNS<Cell<Result<NameBinding<'a>, Determinacy>>>,
-        target_bindings: &PerNS<Cell<Option<NameBinding<'a>>>>,
-        target: Ident,
-    ) {
         // This function is only called for single imports.
-        let ImportKind::Single { id, .. } = import.kind else { unreachable!() };
+        let ImportKind::Single {
+            source, target, ref source_bindings, ref target_bindings, id, ..
+        } = import.kind
+        else {
+            unreachable!()
+        };
+
+        // Skip if the import is of the form `use source as target` and source != target.
+        if source != target {
+            return;
+        }
 
         // Skip if the import was produced by a macro.
         if import.parent_scope.expansion != LocalExpnId::ROOT {
@@ -1323,16 +1325,20 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
 
         // Skip if we are inside a named module (in contrast to an anonymous
         // module defined by a block).
-        if let ModuleKind::Def(..) = import.parent_scope.module.kind {
+        // Skip if the import is public or was used through non scope-based resolution,
+        // e.g. through a module-relative path.
+        if import.used.get() == Some(Used::Other)
+            || self.effective_visibilities.is_exported(self.local_def_id(id))
+        {
             return;
         }
 
-        let mut is_redundant = PerNS { value_ns: None, type_ns: None, macro_ns: None };
+        let mut is_redundant = true;
 
         let mut redundant_span = PerNS { value_ns: None, type_ns: None, macro_ns: None };
 
         self.per_ns(|this, ns| {
-            if let Ok(binding) = source_bindings[ns].get() {
+            if is_redundant && let Ok(binding) = source_bindings[ns].get() {
                 if binding.res() == Res::Err {
                     return;
                 }
@@ -1346,18 +1352,19 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     target_bindings[ns].get(),
                 ) {
                     Ok(other_binding) => {
-                        is_redundant[ns] = Some(
+                        is_redundant =
-                            binding.res() == other_binding.res() && !other_binding.is_ambiguity(),
+                            binding.res() == other_binding.res() && !other_binding.is_ambiguity();
-                        );
+                        if is_redundant {
-                        redundant_span[ns] = Some((other_binding.span, other_binding.is_import()));
+                            redundant_span[ns] =
+                                Some((other_binding.span, other_binding.is_import()));
+                        }
                     }
-                    Err(_) => is_redundant[ns] = Some(false),
+                    Err(_) => is_redundant = false,
                 }
             }
         });
 
-        if !is_redundant.is_empty() && is_redundant.present_items().all(|is_redundant| is_redundant)
+        if is_redundant && !redundant_span.is_empty() {
-        {
             let mut redundant_spans: Vec<_> = redundant_span.present_items().collect();
             redundant_spans.sort();
             redundant_spans.dedup();
@@ -1365,8 +1372,8 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 UNUSED_IMPORTS,
                 id,
                 import.span,
-                format!("the item `{ident}` is imported redundantly"),
+                format!("the item `{source}` is imported redundantly"),
-                BuiltinLintDiagnostics::RedundantImport(redundant_spans, ident),
+                BuiltinLintDiagnostics::RedundantImport(redundant_spans, source),
             );
         }
     }

compiler/rustc_resolve/src/late.rs

@@ -7,23 +7,22 @@
 //! `build_reduced_graph.rs`, `macros.rs` and `imports.rs`.
 
 use crate::errors::ImportsCannotReferTo;
-use crate::BindingKey;
 use crate::{path_names_to_string, rustdoc, BindingError, Finalize, LexicalScopeBinding};
+use crate::{BindingKey, Used};
 use crate::{Module, ModuleOrUniformRoot, NameBinding, ParentScope, PathResult};
 use crate::{ResolutionError, Resolver, Segment, UseError};
 
 use rustc_ast::ptr::P;
-use rustc_ast::visit::{self, AssocCtxt, BoundKind, FnCtxt, FnKind, Visitor};
+use rustc_ast::visit::{AssocCtxt, BoundKind, FnCtxt, FnKind, Visitor};
 use rustc_ast::*;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_errors::{
-    codes::*, struct_span_code_err, Applicability, DiagnosticArgValue, ErrCode, IntoDiagnosticArg,
+    codes::*, struct_span_code_err, Applicability, DiagnosticArgValue, IntoDiagnosticArg, StashKey,
-    StashKey,
 };
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, DefKind, LifetimeRes, NonMacroAttrKind, PartialRes, PerNS};
 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
-use rustc_hir::{BindingAnnotation, PrimTy, TraitCandidate};
+use rustc_hir::{PrimTy, TraitCandidate};
 use rustc_metadata::creader::CStore;
 use rustc_middle::middle::resolve_bound_vars::Set1;
 use rustc_middle::{bug, span_bug};
@@ -3623,7 +3622,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                 // whether they can be shadowed by fresh bindings or not, so force an error.
                 // issues/33118#issuecomment-233962221 (see below) still applies here,
                 // but we have to ignore it for backward compatibility.
-                self.r.record_use(ident, binding, false);
+                self.r.record_use(ident, binding, Used::Other);
                 return None;
             }
             LexicalScopeBinding::Item(binding) => (binding.res(), Some(binding)),
@@ -3638,7 +3637,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
             ) if is_syntactic_ambiguity => {
                 // Disambiguate in favor of a unit struct/variant or constant pattern.
                 if let Some(binding) = binding {
-                    self.r.record_use(ident, binding, false);
+                    self.r.record_use(ident, binding, Used::Other);
                 }
                 Some(res)
             }

compiler/rustc_resolve/src/lib.rs

@@ -175,6 +175,23 @@ enum ImplTraitContext {
     Universal,
 }
 
+/// Used for tracking import use types which will be used for redundant import checking.
+/// ### Used::Scope Example
+///  ```rust,compile_fail
+/// #![deny(unused_imports)]
+/// use std::mem::drop;
+/// fn main() {
+///     let s = Box::new(32);
+///     drop(s);
+/// }
+/// ```
+/// Used::Other is for other situations like module-relative uses.
+#[derive(Clone, Copy, PartialEq, PartialOrd, Debug)]
+enum Used {
+    Scope,
+    Other,
+}
+
 #[derive(Debug)]
 struct BindingError {
     name: Symbol,
@@ -695,7 +712,7 @@ impl<'a> ToNameBinding<'a> for NameBinding<'a> {
 enum NameBindingKind<'a> {
     Res(Res),
     Module(Module<'a>),
-    Import { binding: NameBinding<'a>, import: Import<'a>, used: Cell<bool> },
+    Import { binding: NameBinding<'a>, import: Import<'a> },
 }
 
 impl<'a> NameBindingKind<'a> {
@@ -1784,15 +1801,15 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         false
     }
 
-    fn record_use(&mut self, ident: Ident, used_binding: NameBinding<'a>, is_lexical_scope: bool) {
+    fn record_use(&mut self, ident: Ident, used_binding: NameBinding<'a>, used: Used) {
-        self.record_use_inner(ident, used_binding, is_lexical_scope, used_binding.warn_ambiguity);
+        self.record_use_inner(ident, used_binding, used, used_binding.warn_ambiguity);
     }
 
     fn record_use_inner(
         &mut self,
         ident: Ident,
         used_binding: NameBinding<'a>,
-        is_lexical_scope: bool,
+        used: Used,
         warn_ambiguity: bool,
     ) {
         if let Some((b2, kind)) = used_binding.ambiguity {
@@ -1810,27 +1827,35 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 self.ambiguity_errors.push(ambiguity_error);
             }
         }
-        if let NameBindingKind::Import { import, binding, ref used } = used_binding.kind {
+        if let NameBindingKind::Import { import, binding } = used_binding.kind {
             if let ImportKind::MacroUse { warn_private: true } = import.kind {
                 let msg = format!("macro `{ident}` is private");
                 self.lint_buffer().buffer_lint(PRIVATE_MACRO_USE, import.root_id, ident.span, msg);
             }
             // Avoid marking `extern crate` items that refer to a name from extern prelude,
             // but not introduce it, as used if they are accessed from lexical scope.
-            if is_lexical_scope {
+            if used == Used::Scope {
                 if let Some(entry) = self.extern_prelude.get(&ident.normalize_to_macros_2_0()) {
                     if !entry.introduced_by_item && entry.binding == Some(used_binding) {
                         return;
                     }
                 }
             }
-            used.set(true);
+            let old_used = import.used.get();
-            import.used.set(true);
+            let new_used = Some(used);
+            if new_used > old_used {
+                import.used.set(new_used);
+            }
             if let Some(id) = import.id() {
                 self.used_imports.insert(id);
             }
             self.add_to_glob_map(import, ident);
-            self.record_use_inner(ident, binding, false, warn_ambiguity || binding.warn_ambiguity);
+            self.record_use_inner(
+                ident,
+                binding,
+                Used::Other,
+                warn_ambiguity || binding.warn_ambiguity,
+            );
         }
     }
 
@@ -1985,7 +2010,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     if !entry.is_import() {
                         self.crate_loader(|c| c.process_path_extern(ident.name, ident.span));
                     } else if entry.introduced_by_item {
-                        self.record_use(ident, binding, false);
+                        self.record_use(ident, binding, Used::Other);
                     }
                 }
                 binding
@@ -2115,7 +2140,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         let is_import = name_binding.is_import();
         let span = name_binding.span;
         if let Res::Def(DefKind::Fn, _) = res {
-            self.record_use(ident, name_binding, false);
+            self.record_use(ident, name_binding, Used::Other);
         }
         self.main_def = Some(MainDefinition { res, is_import, span });
     }
@@ -2176,6 +2201,8 @@ struct Finalize {
     /// Whether to report privacy errors or silently return "no resolution" for them,
     /// similarly to speculative resolution.
     report_private: bool,
+    /// Tracks whether an item is used in scope or used relatively to a module.
+    used: Used,
 }
 
 impl Finalize {
@@ -2184,7 +2211,7 @@ impl Finalize {
     }
 
     fn with_root_span(node_id: NodeId, path_span: Span, root_span: Span) -> Finalize {
-        Finalize { node_id, path_span, root_span, report_private: true }
+        Finalize { node_id, path_span, root_span, report_private: true, used: Used::Other }
     }
 }
 

compiler/rustc_resolve/src/macros.rs

@@ -5,7 +5,7 @@ use crate::errors::CannotDetermineMacroResolution;
 use crate::errors::{self, AddAsNonDerive, CannotFindIdentInThisScope};
 use crate::errors::{MacroExpectedFound, RemoveSurroundingDerive};
 use crate::Namespace::*;
-use crate::{BuiltinMacroState, Determinacy, MacroData};
+use crate::{BuiltinMacroState, Determinacy, MacroData, Used};
 use crate::{DeriveData, Finalize, ParentScope, ResolutionError, Resolver, ScopeSet};
 use crate::{ModuleKind, ModuleOrUniformRoot, NameBinding, PathResult, Segment, ToNameBinding};
 use rustc_ast::expand::StrippedCfgItem;
@@ -794,7 +794,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             ) {
                 Ok(binding) => {
                     let initial_res = initial_binding.map(|initial_binding| {
-                        self.record_use(ident, initial_binding, false);
+                        self.record_use(ident, initial_binding, Used::Other);
                         initial_binding.res()
                     });
                     let res = binding.res();

compiler/rustc_session/src/session.rs

@@ -22,7 +22,7 @@ use rustc_errors::emitter::{DynEmitter, HumanEmitter, HumanReadableErrorType};
 use rustc_errors::json::JsonEmitter;
 use rustc_errors::registry::Registry;
 use rustc_errors::{
-    codes::*, fallback_fluent_bundle, DiagCtxt, DiagnosticBuilder, DiagnosticMessage, ErrCode,
+    codes::*, fallback_fluent_bundle, DiagCtxt, DiagnosticBuilder, DiagnosticMessage,
     ErrorGuaranteed, FatalAbort, FluentBundle, IntoDiagnostic, LazyFallbackBundle, TerminalUrl,
 };
 use rustc_macros::HashStable_Generic;

compiler/rustc_span/src/source_map/tests.rs

@@ -1,7 +1,5 @@
 use super::*;
 
-use rustc_data_structures::sync::FreezeLock;
-
 fn init_source_map() -> SourceMap {
     let sm = SourceMap::new(FilePathMapping::empty());
     sm.new_source_file(PathBuf::from("blork.rs").into(), "first line.\nsecond line".to_string());

library/std/src/os/unix/fs.rs

@@ -397,7 +397,6 @@ pub trait OpenOptionsExt {
     ///
     /// ```no_run
     /// # #![feature(rustc_private)]
-    /// use libc;
     /// use std::fs::OpenOptions;
     /// use std::os::unix::fs::OpenOptionsExt;
     ///

src/tools/clippy/src/driver.rs

@@ -28,7 +28,6 @@ use std::fs::read_to_string;
 use std::ops::Deref;
 use std::path::Path;
 use std::process::exit;
-use std::string::ToString;
 
 use anstream::println;
 

src/tools/rust-analyzer/crates/hir-def/src/body/pretty.rs

@@ -6,7 +6,7 @@ use itertools::Itertools;
 
 use crate::{
     hir::{
-        Array, BindingAnnotation, BindingId, CaptureBy, ClosureKind, Literal, LiteralOrConst,
+        Array, BindingAnnotation, CaptureBy, ClosureKind, Literal, LiteralOrConst,
         Movability, Statement,
     },
     pretty::{print_generic_args, print_path, print_type_ref},

src/tools/rust-analyzer/crates/hir-def/src/import_map.rs

@@ -3,7 +3,7 @@
 use std::{fmt, hash::BuildHasherDefault};
 
 use base_db::CrateId;
-use fst::{self, raw::IndexedValue, Automaton, Streamer};
+use fst::{raw::IndexedValue, Automaton, Streamer};
 use hir_expand::name::Name;
 use indexmap::IndexMap;
 use itertools::Itertools;

src/tools/rust-analyzer/crates/hir-def/src/item_tree/lower.rs

@@ -2,12 +2,12 @@
 
 use std::collections::hash_map::Entry;
 
-use hir_expand::{ast_id_map::AstIdMap, span_map::SpanMapRef, HirFileId};
+use hir_expand::{ast_id_map::AstIdMap, span_map::SpanMapRef};
-use syntax::ast::{self, HasModuleItem, HasTypeBounds, IsString};
+use syntax::ast::{HasModuleItem, HasTypeBounds, IsString};
 
 use crate::{
-    generics::{GenericParams, GenericParamsCollector, TypeParamData, TypeParamProvenance},
+    generics::{GenericParamsCollector, TypeParamData, TypeParamProvenance},
-    type_ref::{LifetimeRef, TraitBoundModifier, TraitRef},
+    type_ref::{LifetimeRef, TraitBoundModifier},
     LocalLifetimeParamId, LocalTypeOrConstParamId,
 };
 

src/tools/rust-analyzer/crates/hir-def/src/item_tree/pretty.rs

@@ -1,13 +1,12 @@
 //! `ItemTree` debug printer.
 
-use std::fmt::{self, Write};
+use std::fmt::Write;
 
 use span::ErasedFileAstId;
 
 use crate::{
-    generics::{TypeOrConstParamData, WherePredicate, WherePredicateTypeTarget},
+    generics::{WherePredicate, WherePredicateTypeTarget},
     pretty::{print_path, print_type_bounds, print_type_ref},
-    visibility::RawVisibility,
 };
 
 use super::*;

src/tools/rust-analyzer/crates/hir-def/src/nameres.rs

@@ -57,7 +57,7 @@ pub mod proc_macro;
 #[cfg(test)]
 mod tests;
 
-use std::{cmp::Ord, ops::Deref};
+use std::ops::Deref;
 
 use base_db::{CrateId, Edition, FileId};
 use hir_expand::{

src/tools/rust-analyzer/crates/hir-ty/src/diagnostics/match_check/pat_util.rs

@@ -2,7 +2,7 @@
 //!
 //! Originates from `rustc_hir::pat_util`
 
-use std::iter::{Enumerate, ExactSizeIterator};
+use std::iter::Enumerate;
 
 pub(crate) struct EnumerateAndAdjust<I> {
     enumerate: Enumerate<I>,

src/tools/rust-analyzer/crates/hir-ty/src/mir/eval/shim.rs

@@ -4,11 +4,7 @@
 use std::cmp;
 
 use chalk_ir::TyKind;
-use hir_def::{
+use hir_def::builtin_type::{BuiltinInt, BuiltinUint};
-    builtin_type::{BuiltinInt, BuiltinUint},
-    resolver::HasResolver,
-};
-use hir_expand::mod_path::ModPath;
 
 use super::*;
 

src/tools/rust-analyzer/crates/hir-ty/src/mir/lower.rs

@@ -1,6 +1,6 @@
 //! This module generates a polymorphic MIR from a hir body
 
-use std::{fmt::Write, iter, mem};
+use std::{fmt::Write, mem};
 
 use base_db::{salsa::Cycle, FileId};
 use chalk_ir::{BoundVar, ConstData, DebruijnIndex, TyKind};
@@ -14,23 +14,19 @@ use hir_def::{
     lang_item::{LangItem, LangItemTarget},
     path::Path,
     resolver::{resolver_for_expr, HasResolver, ResolveValueResult, ValueNs},
-    AdtId, DefWithBodyId, EnumVariantId, GeneralConstId, HasModule, ItemContainerId, LocalFieldId,
+    AdtId, EnumVariantId, GeneralConstId, HasModule, ItemContainerId, LocalFieldId,
     Lookup, TraitId, TupleId, TypeOrConstParamId,
 };
 use hir_expand::name::Name;
-use la_arena::ArenaMap;
-use rustc_hash::FxHashMap;
 use syntax::TextRange;
 use triomphe::Arc;
 
 use crate::{
     consteval::ConstEvalError,
-    db::{HirDatabase, InternedClosure},
+    db::InternedClosure,
-    display::HirDisplay,
     infer::{CaptureKind, CapturedItem, TypeMismatch},
     inhabitedness::is_ty_uninhabited_from,
     layout::LayoutError,
-    mapping::ToChalk,
     static_lifetime,
     traits::FnTrait,
     utils::{generics, ClosureSubst},

src/tools/rust-analyzer/crates/hir-ty/src/mir/lower/pattern_matching.rs

@@ -1,6 +1,6 @@
 //! MIR lowering for patterns
 
-use hir_def::{hir::LiteralOrConst, resolver::HasResolver, AssocItemId};
+use hir_def::AssocItemId;
 
 use crate::BindingMode;
 

src/tools/rust-analyzer/crates/ide-assists/src/handlers/generate_delegate_methods.rs

@@ -1,4 +1,4 @@
-use hir::{self, HasCrate, HasVisibility};
+use hir::{HasCrate, HasVisibility};
 use ide_db::{path_transform::PathTransform, FxHashSet};
 use syntax::{
     ast::{

src/tools/rust-analyzer/crates/ide-completion/src/completions/item_list/trait_impl.rs

@@ -31,7 +31,7 @@
 //! }
 //! ```
 
-use hir::{self, HasAttrs};
+use hir::HasAttrs;
 use ide_db::{
     documentation::HasDocs, path_transform::PathTransform,
     syntax_helpers::insert_whitespace_into_node, traits::get_missing_assoc_items, SymbolKind,

src/tools/rust-analyzer/crates/ide-db/src/symbol_index.rs

@@ -31,7 +31,7 @@ use base_db::{
     salsa::{self, ParallelDatabase},
     SourceDatabaseExt, SourceRootId, Upcast,
 };
-use fst::{self, raw::IndexedValue, Automaton, Streamer};
+use fst::{raw::IndexedValue, Automaton, Streamer};
 use hir::{
     db::HirDatabase,
     import_map::{AssocSearchMode, SearchMode},

src/tools/rust-analyzer/crates/rust-analyzer/src/cargo_target_spec.rs

@@ -4,7 +4,7 @@ use std::mem;
 
 use cfg::{CfgAtom, CfgExpr};
 use ide::{Cancellable, CrateId, FileId, RunnableKind, TestId};
-use project_model::{self, CargoFeatures, ManifestPath, TargetKind};
+use project_model::{CargoFeatures, ManifestPath, TargetKind};
 use rustc_hash::FxHashSet;
 use vfs::AbsPathBuf;
 

src/tools/rust-analyzer/crates/rust-analyzer/src/cli/lsif.rs

@@ -13,7 +13,7 @@ use ide_db::{
     LineIndexDatabase,
 };
 use load_cargo::{load_workspace, LoadCargoConfig, ProcMacroServerChoice};
-use lsp_types::{self, lsif};
+use lsp_types::lsif;
 use project_model::{CargoConfig, ProjectManifest, ProjectWorkspace, RustLibSource};
 use rustc_hash::FxHashMap;
 use vfs::{AbsPathBuf, Vfs};

src/tools/rust-analyzer/crates/salsa/salsa-macros/src/query_group.rs

@@ -1,5 +1,4 @@
 //!
-use std::{convert::TryFrom, iter::FromIterator};
 
 use crate::parenthesized::Parenthesized;
 use heck::ToUpperCamelCase;

src/tools/rust-analyzer/crates/salsa/src/debug.rs

@@ -5,7 +5,6 @@ use crate::durability::Durability;
 use crate::plumbing::QueryStorageOps;
 use crate::Query;
 use crate::QueryTable;
-use std::iter::FromIterator;
 
 /// Additional methods on queries that can be used to "peek into"
 /// their current state. These methods are meant for debugging and

src/tools/rust-analyzer/crates/salsa/src/derived.rs

@@ -13,7 +13,6 @@ use crate::Runtime;
 use crate::{Database, DatabaseKeyIndex, QueryDb, Revision};
 use parking_lot::RwLock;
 use std::borrow::Borrow;
-use std::convert::TryFrom;
 use std::hash::Hash;
 use std::marker::PhantomData;
 use triomphe::Arc;

src/tools/rust-analyzer/crates/salsa/src/input.rs

@@ -14,7 +14,6 @@ use crate::Runtime;
 use crate::{DatabaseKeyIndex, QueryDb};
 use indexmap::map::Entry;
 use parking_lot::RwLock;
-use std::convert::TryFrom;
 use std::iter;
 use tracing::debug;
 

src/tools/rust-analyzer/crates/salsa/src/interned.rs

@@ -13,7 +13,6 @@ use crate::{Database, DatabaseKeyIndex, QueryDb};
 use parking_lot::RwLock;
 use rustc_hash::FxHashMap;
 use std::collections::hash_map::Entry;
-use std::convert::From;
 use std::fmt::Debug;
 use std::hash::Hash;
 use triomphe::Arc;

tests/ui/lint/unused/lint-unused-imports.rs

@@ -66,7 +66,6 @@ pub mod bar {
 
 fn g() {
     use self::g; //~ ERROR unused import: `self::g`
-    //~^ ERROR the item `g` is imported redundantly
     fn f() {
         self::g();
     }
@@ -76,7 +75,6 @@ fn g() {
 #[allow(unused_variables)]
 fn h() {
     use test2::foo; //~ ERROR unused import: `test2::foo`
-    //~^ ERROR the item `foo` is imported redundantly
     let foo = 0;
 }
 

tests/ui/lint/unused/lint-unused-imports.stderr

@@ -34,36 +34,14 @@ error: unused import: `foo::Square`
 LL |         use foo::Square;
    |             ^^^^^^^^^^^
 
-error: the item `g` is imported redundantly
-  --> $DIR/lint-unused-imports.rs:68:9
-   |
-LL | / fn g() {
-LL | |     use self::g;
-   | |         ^^^^^^^
-LL | |
-LL | |     fn f() {
-LL | |         self::g();
-LL | |     }
-LL | | }
-   | |_- the item `g` is already defined here
-
 error: unused import: `self::g`
   --> $DIR/lint-unused-imports.rs:68:9
    |
 LL |     use self::g;
    |         ^^^^^^^
 
-error: the item `foo` is imported redundantly
-  --> $DIR/lint-unused-imports.rs:78:9
-   |
-LL | use test2::{foo, bar};
-   |             --- the item `foo` is already imported here
-...
-LL |     use test2::foo;
-   |         ^^^^^^^^^^
-
 error: unused import: `test2::foo`
-  --> $DIR/lint-unused-imports.rs:78:9
+  --> $DIR/lint-unused-imports.rs:77:9
    |
 LL |     use test2::foo;
    |         ^^^^^^^^^^
@@ -74,5 +52,5 @@ error: unused import: `test::B2`
 LL | use test::B2;
    |     ^^^^^^^^
 
-error: aborting due to 10 previous errors
+error: aborting due to 8 previous errors
 

tests/ui/lint/use-redundant/use-redundant-prelude-rust-2015.rs

@@ -0,0 +1,19 @@
+//@ check-pass
+#![warn(unused_imports)]
+
+
+use std::option::Option::Some;//~ WARNING the item `Some` is imported redundantly
+use std::option::Option::None; //~ WARNING the item `None` is imported redundantly
+
+use std::result::Result::Ok;//~ WARNING the item `Ok` is imported redundantly
+use std::result::Result::Err;//~ WARNING the item `Err` is imported redundantly
+use std::convert::{TryFrom, TryInto};
+
+fn main() {
+    let _a: Option<i32> = Some(1);
+    let _b: Option<i32>  = None;
+    let _c: Result<i32, String> = Ok(1);
+    let _d: Result<i32, &str> = Err("error");
+    let _e: Result<i32, _> = 8u8.try_into();
+    let _f: Result<i32, _> = i32::try_from(8u8);
+}

tests/ui/lint/use-redundant/use-redundant-prelude-rust-2015.stderr

@@ -0,0 +1,44 @@
+warning: the item `Some` is imported redundantly
+  --> $DIR/use-redundant-prelude-rust-2015.rs:5:5
+   |
+LL | use std::option::Option::Some;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+  --> $SRC_DIR/std/src/prelude/mod.rs:LL:COL
+   |
+   = note: the item `Some` is already defined here
+   |
+note: the lint level is defined here
+  --> $DIR/use-redundant-prelude-rust-2015.rs:2:9
+   |
+LL | #![warn(unused_imports)]
+   |         ^^^^^^^^^^^^^^
+
+warning: the item `None` is imported redundantly
+  --> $DIR/use-redundant-prelude-rust-2015.rs:6:5
+   |
+LL | use std::option::Option::None;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+  --> $SRC_DIR/std/src/prelude/mod.rs:LL:COL
+   |
+   = note: the item `None` is already defined here
+
+warning: the item `Ok` is imported redundantly
+  --> $DIR/use-redundant-prelude-rust-2015.rs:8:5
+   |
+LL | use std::result::Result::Ok;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^
+  --> $SRC_DIR/std/src/prelude/mod.rs:LL:COL
+   |
+   = note: the item `Ok` is already defined here
+
+warning: the item `Err` is imported redundantly
+  --> $DIR/use-redundant-prelude-rust-2015.rs:9:5
+   |
+LL | use std::result::Result::Err;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^
+  --> $SRC_DIR/std/src/prelude/mod.rs:LL:COL
+   |
+   = note: the item `Err` is already defined here
+
+warning: 4 warnings emitted
+

tests/ui/lint/use-redundant/use-redundant-prelude-rust-2021.rs

@@ -0,0 +1,11 @@
+//@ check-pass
+//@ edition:2021
+#![warn(unused_imports)]
+
+use std::convert::TryFrom;//~ WARNING the item `TryFrom` is imported redundantly
+use std::convert::TryInto;//~ WARNING the item `TryInto` is imported redundantly
+
+fn main() {
+    let _e: Result<i32, _> = 8u8.try_into();
+    let _f: Result<i32, _> = i32::try_from(8u8);
+}

tests/ui/lint/use-redundant/use-redundant-prelude-rust-2021.stderr

@@ -0,0 +1,26 @@
+warning: the item `TryFrom` is imported redundantly
+  --> $DIR/use-redundant-prelude-rust-2021.rs:5:5
+   |
+LL | use std::convert::TryFrom;
+   |     ^^^^^^^^^^^^^^^^^^^^^
+  --> $SRC_DIR/std/src/prelude/mod.rs:LL:COL
+   |
+   = note: the item `TryFrom` is already defined here
+   |
+note: the lint level is defined here
+  --> $DIR/use-redundant-prelude-rust-2021.rs:3:9
+   |
+LL | #![warn(unused_imports)]
+   |         ^^^^^^^^^^^^^^
+
+warning: the item `TryInto` is imported redundantly
+  --> $DIR/use-redundant-prelude-rust-2021.rs:6:5
+   |
+LL | use std::convert::TryInto;
+   |     ^^^^^^^^^^^^^^^^^^^^^
+  --> $SRC_DIR/std/src/prelude/mod.rs:LL:COL
+   |
+   = note: the item `TryInto` is already defined here
+
+warning: 2 warnings emitted
+

tests/ui/rust-2018/remove-extern-crate.fixed

@@ -6,6 +6,7 @@
 
 #![warn(rust_2018_idioms)]
 #![allow(dropping_copy_types)]
+#![allow(unused_imports)]
 
  //~ WARNING unused extern crate
 // Shouldn't suggest changing to `use`, as `another_name`

tests/ui/rust-2018/remove-extern-crate.rs

@@ -6,6 +6,7 @@
 
 #![warn(rust_2018_idioms)]
 #![allow(dropping_copy_types)]
+#![allow(unused_imports)]
 
 extern crate core; //~ WARNING unused extern crate
 // Shouldn't suggest changing to `use`, as `another_name`

tests/ui/rust-2018/remove-extern-crate.stderr

@@ -1,5 +1,5 @@
 warning: unused extern crate
-  --> $DIR/remove-extern-crate.rs:10:1
+  --> $DIR/remove-extern-crate.rs:11:1
    |
 LL | extern crate core;
    | ^^^^^^^^^^^^^^^^^^ help: remove it
@@ -12,7 +12,7 @@ LL | #![warn(rust_2018_idioms)]
    = note: `#[warn(unused_extern_crates)]` implied by `#[warn(rust_2018_idioms)]`
 
 warning: `extern crate` is not idiomatic in the new edition
-  --> $DIR/remove-extern-crate.rs:34:5
+  --> $DIR/remove-extern-crate.rs:35:5
    |
 LL |     extern crate core;
    |     ^^^^^^^^^^^^^^^^^^
@@ -23,7 +23,7 @@ LL |     use core;
    |     ~~~
 
 warning: `extern crate` is not idiomatic in the new edition
-  --> $DIR/remove-extern-crate.rs:44:5
+  --> $DIR/remove-extern-crate.rs:45:5
    |
 LL |     pub extern crate core;
    |     ^^^^^^^^^^^^^^^^^^^^^^