fixes rust-lang#121331

compiler/rustc_resolve/src/check_unused.rs

@@ -27,18 +27,23 @@ use crate::imports::ImportKind;
 use crate::module_to_string;
 use crate::Resolver;
 
-use crate::NameBindingKind;
+use crate::{LexicalScopeBinding, NameBindingKind};
 use rustc_ast as ast;
 use rustc_ast::visit::{self, Visitor};
 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};
-use rustc_session::lint::builtin::{MACRO_USE_EXTERN_CRATE, UNUSED_EXTERN_CRATES, UNUSED_IMPORTS};
+use rustc_session::lint::builtin::{
+    MACRO_USE_EXTERN_CRATE, UNUSED_EXTERN_CRATES, UNUSED_IMPORTS, UNUSED_QUALIFICATIONS,
+};
 use rustc_session::lint::BuiltinLintDiag;
+use rustc_span::symbol::sym;
 use rustc_span::symbol::{kw, Ident};
 use rustc_span::{Span, DUMMY_SP};
+use thin_vec::ThinVec;
 
+#[derive(Debug)]
 struct UnusedImport {
     use_tree: ast::UseTree,
     use_tree_id: ast::NodeId,
@@ -494,6 +499,39 @@ impl Resolver<'_, '_> {
         }
 
         let unused_imports = visitor.unused_imports;
+
+        // The lint fixes for unused_import and unnecessary_qualification may conflict.
+        // Deleting both unused imports and unnecessary segments of an item may result
+        // in the item not being found.
+        for v in &self.potentially_unnecessary_qualification {
+            if let LexicalScopeBinding::Item(name_binding) = v.binding
+                && let NameBindingKind::Import { binding: _, import } = name_binding.kind
+                && let Some(unused_import) = unused_imports.get(&import.root_id)
+                && let Some(id) = import.id()
+                && unused_import.unused.contains(&id)
+            {
+                let def_id = self.local_def_id(id);
+                if let Some(attr) = tcx.get_attr(def_id, sym::allow) {
+                    debug!("surechen attr:{:?}", attr);
+                    for item in attr.meta_item_list().unwrap_or_else(ThinVec::new) {
+                        debug!("surechen item:{:?}", item);
+                        if !item.has_name(sym::unused_imports) {
+                            debug!("surechen yes item:{:?}", item);
+                            continue;
+                        }
+                    }
+                }
+            }
+
+            self.lint_buffer.buffer_lint_with_diagnostic(
+                UNUSED_QUALIFICATIONS,
+                v.finalize.node_id,
+                v.finalize.path_span,
+                "unnecessary qualification",
+                BuiltinLintDiag::UnusedQualifications { removal_span: v.span },
+            );
+        }
+
         let mut check_redundant_imports = FxIndexSet::default();
         for module in self.arenas.local_modules().iter() {
             for (_key, resolution) in self.resolutions(*module).borrow().iter() {

compiler/rustc_resolve/src/imports.rs

@@ -1352,6 +1352,11 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     target_bindings[ns].get(),
                 ) {
                     Ok(other_binding) => {
+                        debug!(
+                            "surechen check_for_redundant_imports other_binding:{:?}",
+                            other_binding
+                        );
+                        debug!("surechen check_for_redundant_imports binding:{:?}", binding);
                         is_redundant =
                             binding.res() == other_binding.res() && !other_binding.is_ambiguity();
                         if is_redundant {

compiler/rustc_resolve/src/late.rs

@@ -580,6 +580,14 @@ impl MaybeExported<'_> {
     }
 }
 
+/// Used for recording UnnecessaryQualification.
+#[derive(Debug)]
+pub(crate) struct UnnecessaryQualification<'a> {
+    pub binding: LexicalScopeBinding<'a>,
+    pub finalize: Finalize,
+    pub span: Span,
+}
+
 #[derive(Default)]
 struct DiagMetadata<'ast> {
     /// The current trait's associated items' ident, used for diagnostic suggestions.
@@ -4653,20 +4661,15 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
             let ns = if i + 1 == path.len() { ns } else { TypeNS };
             let res = self.r.partial_res_map.get(&seg.id?)?.full_res()?;
             let binding = self.resolve_ident_in_lexical_scope(seg.ident, ns, None, None)?;
-
-            (res == binding.res()).then_some(seg)
+            (res == binding.clone().res()).then_some((seg, binding))
         });
 
         if let Some(unqualified) = unqualified {
-            self.r.lint_buffer.buffer_lint_with_diagnostic(
-                lint::builtin::UNUSED_QUALIFICATIONS,
-                finalize.node_id,
-                finalize.path_span,
-                "unnecessary qualification",
-                lint::BuiltinLintDiag::UnusedQualifications {
-                    removal_span: path[0].ident.span.until(unqualified.ident.span),
-                },
-            );
+            self.r.potentially_unnecessary_qualification.push(UnnecessaryQualification {
+                binding: unqualified.1,
+                finalize: finalize,
+                span: path[0].ident.span.until(unqualified.0.ident.span),
+            });
         }
     }
 }

compiler/rustc_resolve/src/lib.rs

@@ -68,7 +68,7 @@ use std::fmt;
 
 use diagnostics::{ImportSuggestion, LabelSuggestion, Suggestion};
 use imports::{Import, ImportData, ImportKind, NameResolution};
-use late::{HasGenericParams, PathSource, PatternSource};
+use late::{HasGenericParams, PathSource, PatternSource, UnnecessaryQualification};
 use macros::{MacroRulesBinding, MacroRulesScope, MacroRulesScopeRef};
 
 use crate::effective_visibilities::EffectiveVisibilitiesVisitor;
@@ -372,7 +372,7 @@ impl<'a> From<&'a ast::PathSegment> for Segment {
 /// This refers to the thing referred by a name. The difference between `Res` and `Item` is that
 /// items are visible in their whole block, while `Res`es only from the place they are defined
 /// forward.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 enum LexicalScopeBinding<'a> {
     Item(NameBinding<'a>),
     Res(Res),
@@ -1105,6 +1105,8 @@ pub struct Resolver<'a, 'tcx> {
 
     potentially_unused_imports: Vec<Import<'a>>,
 
+    potentially_unnecessary_qualification: Vec<UnnecessaryQualification<'a>>,
+
     /// Table for mapping struct IDs into struct constructor IDs,
     /// it's not used during normal resolution, only for better error reporting.
     /// Also includes of list of each fields visibility
@@ -1464,6 +1466,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             local_macro_def_scopes: FxHashMap::default(),
             name_already_seen: FxHashMap::default(),
             potentially_unused_imports: Vec::new(),
+            potentially_unnecessary_qualification: Default::default(),
             struct_constructors: Default::default(),
             unused_macros: Default::default(),
             unused_macro_rules: Default::default(),

tests/ui/lint/lint-qualification.fixed

@@ -21,8 +21,8 @@ fn main() {
     //~^ ERROR: unnecessary qualification
     //~| ERROR: unnecessary qualification
 
-    use std::fmt;
-    let _: fmt::Result = Ok(()); //~ ERROR: unnecessary qualification
+     //~ ERROR: unused import: `std::fmt`
+    let _: std::fmt::Result = Ok(()); // issue #121999
 
     let _ = <bool as Default>::default(); // issue #121999
     //~^ ERROR: unnecessary qualification

tests/ui/lint/lint-qualification.rs

@@ -21,8 +21,9 @@ fn main() {
     //~^ ERROR: unnecessary qualification
     //~| ERROR: unnecessary qualification
 
-    use std::fmt;
-    let _: std::fmt::Result = Ok(()); //~ ERROR: unnecessary qualification
+    #[deny(unused_imports)]
+    use std::fmt; //~ ERROR: unused import: `std::fmt`
+    let _: std::fmt::Result = Ok(()); // issue #121331
 
     let _ = <bool as ::std::default::Default>::default(); // issue #121999
     //~^ ERROR: unnecessary qualification

tests/ui/lint/lint-qualification.stderr

@@ -75,20 +75,20 @@ LL -     let _: std::vec::Vec<String> = std::vec::Vec::<String>::new();
 LL +     let _: std::vec::Vec<String> = Vec::<String>::new();
    |
 
-error: unnecessary qualification
-  --> $DIR/lint-qualification.rs:25:12
-   |
-LL |     let _: std::fmt::Result = Ok(());
-   |            ^^^^^^^^^^^^^^^^
+error: unused import: `std::fmt`
+  --> $DIR/lint-qualification.rs:25:9
    |
-help: remove the unnecessary path segments
+LL |     use std::fmt;
+   |         ^^^^^^^^
    |
-LL -     let _: std::fmt::Result = Ok(());
-LL +     let _: fmt::Result = Ok(());
+note: the lint level is defined here
+  --> $DIR/lint-qualification.rs:24:12
    |
+LL |     #[deny(unused_imports)]
+   |            ^^^^^^^^^^^^^^
 
 error: unnecessary qualification
-  --> $DIR/lint-qualification.rs:27:13
+  --> $DIR/lint-qualification.rs:28:13
    |
 LL |     let _ = <bool as ::std::default::Default>::default(); // issue #121999
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/lint/unused/lint-qualification-issue-121331.rs

@@ -0,0 +1,27 @@
+//@ run-rustfix
+//@ edition:2021
+#![deny(unused_qualifications)]
+#![feature(coroutines, coroutine_trait)]
+
+use std::ops::{
+    Coroutine,
+    CoroutineState::{self, *},
+};
+use std::pin::Pin;
+
+fn finish<T>(mut amt: usize, mut t: T) -> T::Return
+    where T: Coroutine<(), Yield = ()> + Unpin,
+{
+    loop {
+        match Pin::new(&mut t).resume(()) {
+            CoroutineState::Yielded(()) => amt = amt.checked_sub(1).unwrap(),
+            CoroutineState::Complete(ret) => {
+                assert_eq!(amt, 0);
+                return ret
+            }
+        }
+    }
+
+}
+
+pub fn main() {}