Auto merge of #114417 - chinedufn:fix-expect-unused-in-impl-block-rus…

…t-issue-114416, r=cjgillot

Fix multiple `expect` attribs in impl block

Closes #114416

compiler/rustc_passes/src/dead.rs

@@ -1,6 +1,7 @@
-// This implements the dead-code warning pass. It follows middle::reachable
-// closely. The idea is that all reachable symbols are live, codes called
-// from live codes are live, and everything else is dead.
+// This implements the dead-code warning pass.
+// All reachable symbols are live, code called from live code is live, code with certain lint
+// expectations such as `#[expect(unused)]` and `#[expect(dead_code)]` is live, and everything else
+// is dead.
 
 use hir::def_id::{LocalDefIdMap, LocalDefIdSet};
 use itertools::Itertools;
@@ -747,7 +748,7 @@ fn live_symbols_and_ignored_derived_traits(
  (symbol_visitor.live_symbols, symbol_visitor.ignored_derived_traits)
 }
 
-struct DeadVariant {
+struct DeadItem {
  def_id: LocalDefId,
  name: Symbol,
  level: lint::Level,
@@ -785,7 +786,13 @@ impl<'tcx> DeadVisitor<'tcx> {
  ShouldWarnAboutField::Yes(is_positional)
  }
 
- fn warn_multiple_dead_codes(
+ // # Panics
+ // All `dead_codes` must have the same lint level, otherwise we will intentionally ICE.
+ // This is because we emit a multi-spanned lint using the lint level of the `dead_codes`'s
+ // first local def id.
+ // Prefer calling `Self.warn_dead_code` or `Self.warn_dead_code_grouped_by_lint_level`
+ // since those methods group by lint level before calling this method.
+ fn lint_at_single_level(
  &self,
  dead_codes: &[LocalDefId],
  participle: &str,
@@ -796,6 +803,15 @@ impl<'tcx> DeadVisitor<'tcx> {
  return;
  };
  let tcx = self.tcx;
+
+ let first_hir_id = tcx.hir().local_def_id_to_hir_id(first_id);
+ let first_lint_level = tcx.lint_level_at_node(lint::builtin::DEAD_CODE, first_hir_id).0;
+ assert!(dead_codes.iter().skip(1).all(|id| {
+ let hir_id = tcx.hir().local_def_id_to_hir_id(*id);
+ let level = tcx.lint_level_at_node(lint::builtin::DEAD_CODE, hir_id).0;
+ level == first_lint_level
+ }));
+
  let names: Vec<_> =
  dead_codes.iter().map(|&def_id| tcx.item_name(def_id.to_def_id())).collect();
  let spans: Vec<_> = dead_codes
@@ -876,31 +892,26 @@ impl<'tcx> DeadVisitor<'tcx> {
  }
  };
 
- self.tcx.emit_spanned_lint(
- lint,
- tcx.hir().local_def_id_to_hir_id(first_id),
- MultiSpan::from_spans(spans),
- diag,
- );
+ self.tcx.emit_spanned_lint(lint, first_hir_id, MultiSpan::from_spans(spans), diag);
  }
 
- fn warn_dead_fields_and_variants(
+ fn warn_multiple(
  &self,
  def_id: LocalDefId,
  participle: &str,
- dead_codes: Vec<DeadVariant>,
+ dead_codes: Vec<DeadItem>,
  is_positional: bool,
  ) {
  let mut dead_codes = dead_codes
  .iter()
  .filter(|v| !v.name.as_str().starts_with('_'))
- .collect::<Vec<&DeadVariant>>();
+ .collect::<Vec<&DeadItem>>();
  if dead_codes.is_empty() {
  return;
  }
  dead_codes.sort_by_key(|v| v.level);
  for (_, group) in &dead_codes.into_iter().group_by(|v| v.level) {
- self.warn_multiple_dead_codes(
+ self.lint_at_single_level(
  &group.map(|v| v.def_id).collect::<Vec<_>>(),
  participle,
  Some(def_id),
@@ -910,7 +921,7 @@ impl<'tcx> DeadVisitor<'tcx> {
  }
 
  fn warn_dead_code(&mut self, id: LocalDefId, participle: &str) {
- self.warn_multiple_dead_codes(&[id], participle, None, false);
+ self.lint_at_single_level(&[id], participle, None, false);
  }
 
  fn check_definition(&mut self, def_id: LocalDefId) {
@@ -954,17 +965,16 @@ fn check_mod_deathness(tcx: TyCtxt<'_>, module: LocalModDefId) {
  if let hir::ItemKind::Impl(impl_item) = tcx.hir().item(item).kind {
  let mut dead_items = Vec::new();
  for item in impl_item.items {
- let did = item.id.owner_id.def_id;
- if !visitor.is_live_code(did) {
- dead_items.push(did)
+ let def_id = item.id.owner_id.def_id;
+ if !visitor.is_live_code(def_id) {
+ let name = tcx.item_name(def_id.to_def_id());
+ let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
+ let level = tcx.lint_level_at_node(lint::builtin::DEAD_CODE, hir_id).0;
+
+ dead_items.push(DeadItem { def_id, name, level })
  }
  }
- visitor.warn_multiple_dead_codes(
- &dead_items,
- "used",
- Some(item.owner_id.def_id),
- false,
- );
+ visitor.warn_multiple(item.owner_id.def_id, "used", dead_items, false);
  }
 
  if !live_symbols.contains(&item.owner_id.def_id) {
@@ -988,7 +998,7 @@ fn check_mod_deathness(tcx: TyCtxt<'_>, module: LocalModDefId) {
  // Record to group diagnostics.
  let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
  let level = tcx.lint_level_at_node(lint::builtin::DEAD_CODE, hir_id).0;
- dead_variants.push(DeadVariant { def_id, name: variant.name, level });
+ dead_variants.push(DeadItem { def_id, name: variant.name, level });
  continue;
  }
 
@@ -1013,21 +1023,16 @@ fn check_mod_deathness(tcx: TyCtxt<'_>, module: LocalModDefId) {
  hir_id,
  )
  .0;
- Some(DeadVariant { def_id, name: field.name, level })
+ Some(DeadItem { def_id, name: field.name, level })
  } else {
  None
  }
  })
  .collect();
- visitor.warn_dead_fields_and_variants(def_id, "read", dead_fields, is_positional)
+ visitor.warn_multiple(def_id, "read", dead_fields, is_positional);
  }
 
- visitor.warn_dead_fields_and_variants(
- item.owner_id.def_id,
- "constructed",
- dead_variants,
- false,
- );
+ visitor.warn_multiple(item.owner_id.def_id, "constructed", dead_variants, false);
  }
  }
 

tests/ui/lint/rfc-2383-lint-reason/expect_unused_inside_impl_block.rs

@@ -0,0 +1,30 @@
+// check-pass
+// incremental
+
+#![feature(lint_reasons)]
+#![warn(unused)]
+
+struct OneUnused;
+struct TwoUnused;
+
+impl OneUnused {
+ #[expect(unused)]
+ fn unused() {}
+}
+
+impl TwoUnused {
+ #[expect(unused)]
+ fn unused1(){}
+
+ // This unused method has `#[expect(unused)]`, so the compiler should not emit a warning.
+ // This ui test was added after a regression in the compiler where it did not recognize multiple
+ // `#[expect(unused)]` annotations inside of impl blocks.
+ // issue 114416
+ #[expect(unused)]
+ fn unused2(){}
+}
+
+fn main() {
+ let _ = OneUnused;
+ let _ = TwoUnused;
+}