resolve: only report unused import for no-reexports lint

compiler/rustc_resolve/src/check_unused.rs

@@ -23,6 +23,7 @@
 //  - `check_crate` finally emits the diagnostics based on the data generated
 //    in the last step
 
+use crate::fluent_generated as fluent;
 use crate::imports::ImportKind;
 use crate::module_to_string;
 use crate::Resolver;
@@ -487,4 +488,20 @@ impl Resolver<'_, '_> {
             );
         }
     }
+
+    pub(crate) fn check_no_reexports(&mut self) {
+        for import in &self.no_reexports_imports {
+            let ImportKind::Glob { id, .. } = import.kind else {
+                unreachable!();
+            };
+            if !import.used.get() {
+                self.lint_buffer.buffer_lint(
+                    UNUSED_IMPORTS,
+                    id,
+                    import.span,
+                    fluent::resolve_glob_import_doesnt_reexport,
+                );
+            }
+        }
+    }
 }

compiler/rustc_resolve/src/imports.rs

@@ -8,7 +8,7 @@ use crate::errors::{
     ItemsInTraitsAreNotImportable,
 };
 use crate::Determinacy::{self, *};
-use crate::{fluent_generated as fluent, Namespace::*};
+use crate::Namespace::*;
 use crate::{module_to_string, names_to_string, ImportSuggestion};
 use crate::{AmbiguityKind, BindingKey, ModuleKind, ResolutionError, Resolver, Segment};
 use crate::{Finalize, Module, ModuleOrUniformRoot, ParentScope, PerNS, ScopeSet};
@@ -965,7 +965,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     id,
                     ..
                 } => (source, target, source_bindings, target_bindings, type_ns_only, id),
-                ImportKind::Glob { is_prelude, ref max_vis, id } => {
+                ImportKind::Glob { is_prelude, ref max_vis, .. } => {
                     if import.module_path.len() <= 1 {
                         // HACK(eddyb) `lint_if_path_starts_with_module` needs at least
                         // 2 segments, so the `resolve_path` above won't trigger it.
@@ -992,7 +992,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     && let Some(max_vis) = max_vis.get()
                     && !max_vis.is_at_least(import.expect_vis(), self.tcx)
                     {
-                        self.lint_buffer.buffer_lint(UNUSED_IMPORTS, id, import.span, fluent::resolve_glob_import_doesnt_reexport);
+                        self.no_reexports_imports.push(import);
                     }
                     return None;
                 }

compiler/rustc_resolve/src/lib.rs

@@ -954,6 +954,8 @@ pub struct Resolver<'a, 'tcx> {
     /// All non-determined imports.
     indeterminate_imports: Vec<Import<'a>>,
 
+    no_reexports_imports: Vec<Import<'a>>,
+
     // Spans for local variables found during pattern resolution.
     // Used for suggestions during error reporting.
     pat_span_map: NodeMap<Span>,
@@ -1336,6 +1338,8 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             determined_imports: Vec::new(),
             indeterminate_imports: Vec::new(),
 
+            no_reexports_imports: Vec::new(),
+
             pat_span_map: Default::default(),
             partial_res_map: Default::default(),
             import_res_map: Default::default(),
@@ -1605,6 +1609,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             self.tcx.sess.time("late_resolve_crate", || self.late_resolve_crate(krate));
             self.tcx.sess.time("resolve_main", || self.resolve_main());
             self.tcx.sess.time("resolve_check_unused", || self.check_unused(krate));
+            self.tcx.sess.time("resolve_check_no_reexports", || self.check_no_reexports());
             self.tcx.sess.time("resolve_report_errors", || self.report_errors(krate));
             self.tcx
                 .sess

tests/ui/imports/no-reexports-but-used.rs

@@ -0,0 +1,16 @@
+// check-pass
+
+// https://github.com/rust-lang/rust/issues/115966
+
+#![deny(unused_imports)]
+
+mod a {
+    mod b {
+        pub(crate) const C: &str = "123";
+    }
+    pub use self::b::*;
+}
+
+fn main() {
+    let _ = a::C;
+}