Give items related to issue 33140 a more meaningful name

Author: fmease

compiler/rustc_middle/src/query/mod.rs

@@ -847,8 +847,10 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query issue33140_self_ty(key: DefId) -> Option<ty::EarlyBinder<ty::Ty<'tcx>>> {
-        desc { |tcx| "computing Self type wrt issue #33140 `{}`", tcx.def_path_str(key) }
+    query self_ty_of_trait_impl_enabling_order_dep_trait_object_hack(
+        key: DefId
+    ) -> Option<ty::EarlyBinder<ty::Ty<'tcx>>> {
+        desc { |tcx| "computing self type wrt issue #33140 `{}`", tcx.def_path_str(key) }
     }
 
     /// Maps a `DefId` of a type to a list of its inherent impls.

compiler/rustc_middle/src/ty/mod.rs

@@ -1503,14 +1503,14 @@ pub enum ImplOverlapKind {
         /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait
         marker: bool,
     },
-    /// These impls are allowed to overlap, but that raises
-    /// an issue #33140 future-compatibility warning.
+    /// These impls are allowed to overlap, but that raises an
+    /// issue #33140 future-compatibility warning (tracked in #56484).
     ///
     /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's
     /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different.
     ///
-    /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied
-    /// that difference, making what reduces to the following set of impls:
+    /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied on
+    /// that difference, doing what reduces to the following set of impls:
     ///
     /// ```compile_fail,(E0119)
     /// trait Trait {}
@@ -1535,7 +1535,7 @@ pub enum ImplOverlapKind {
     /// 4. Neither of the impls can have any where-clauses.
     ///
     /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed.
-    Issue33140,
+    FutureCompatOrderDepTraitObjects,
 }
 
 /// Useful source information about where a desugared associated type for an
@@ -1730,27 +1730,26 @@ impl<'tcx> TyCtxt<'tcx> {
             | (ImplPolarity::Negative, ImplPolarity::Negative) => {}
         };
 
-        let is_marker_overlap = {
-            let is_marker_impl =
-                |trait_ref: TraitRef<'_>| -> bool { self.trait_def(trait_ref.def_id).is_marker };
-            is_marker_impl(trait_ref1) && is_marker_impl(trait_ref2)
-        };
+        let is_marker_impl = |trait_ref: TraitRef<'_>| self.trait_def(trait_ref.def_id).is_marker;
+        let is_marker_overlap = is_marker_impl(trait_ref1) && is_marker_impl(trait_ref2);
 
         if is_marker_overlap {
-            Some(ImplOverlapKind::Permitted { marker: true })
-        } else {
-            if let Some(self_ty1) = self.issue33140_self_ty(def_id1) {
-                if let Some(self_ty2) = self.issue33140_self_ty(def_id2) {
-                    if self_ty1 == self_ty2 {
-                        return Some(ImplOverlapKind::Issue33140);
-                    } else {
-                        debug!("found {self_ty1:?} != {self_ty2:?}");
-                    }
-                }
-            }
+            return Some(ImplOverlapKind::Permitted { marker: true });
+        }
 
-            None
+        if let Some(self_ty1) =
+            self.self_ty_of_trait_impl_enabling_order_dep_trait_object_hack(def_id1)
+            && let Some(self_ty2) =
+                self.self_ty_of_trait_impl_enabling_order_dep_trait_object_hack(def_id2)
+        {
+            if self_ty1 == self_ty2 {
+                return Some(ImplOverlapKind::FutureCompatOrderDepTraitObjects);
+            } else {
+                debug!("found {self_ty1:?} != {self_ty2:?}");
+            }
         }
+
+        None
     }
 
     /// Returns `ty::VariantDef` if `res` refers to a struct,

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2001,7 +2001,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                     // any associated items and there are no where-clauses.
                     //
                     // We can just arbitrarily drop one of the impls.
-                    Some(ty::ImplOverlapKind::Issue33140) => {
+                    Some(ty::ImplOverlapKind::FutureCompatOrderDepTraitObjects) => {
                         assert_eq!(other.evaluation, victim.evaluation);
                         DropVictim::Yes
                     }

compiler/rustc_trait_selection/src/traits/specialize/mod.rs

@@ -453,7 +453,7 @@ fn report_conflicting_impls<'tcx>(
             overlap.trait_ref.print_trait_sugared(),
             overlap.self_ty.map_or_else(String::new, |ty| format!(" for type `{ty}`")),
             match used_to_be_allowed {
-                Some(FutureCompatOverlapErrorKind::Issue33140) => ": (E0119)",
+                Some(FutureCompatOverlapErrorKind::OrderDepTraitObjects) => ": (E0119)",
                 _ => "",
             }
         )
@@ -480,7 +480,7 @@ fn report_conflicting_impls<'tcx>(
         }
         Some(kind) => {
             let lint = match kind {
-                FutureCompatOverlapErrorKind::Issue33140 => ORDER_DEPENDENT_TRAIT_OBJECTS,
+                FutureCompatOverlapErrorKind::OrderDepTraitObjects => ORDER_DEPENDENT_TRAIT_OBJECTS,
                 FutureCompatOverlapErrorKind::LeakCheck => COHERENCE_LEAK_CHECK,
             };
             tcx.node_span_lint(

compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs

@@ -11,7 +11,7 @@ pub use rustc_middle::traits::specialization_graph::*;
 
 #[derive(Copy, Clone, Debug)]
 pub enum FutureCompatOverlapErrorKind {
-    Issue33140,
+    OrderDepTraitObjects,
     LeakCheck,
 }
 
@@ -150,10 +150,10 @@ impl<'tcx> Children {
                 {
                     match overlap_kind {
                         ty::ImplOverlapKind::Permitted { marker: _ } => {}
-                        ty::ImplOverlapKind::Issue33140 => {
+                        ty::ImplOverlapKind::FutureCompatOrderDepTraitObjects => {
                             *last_lint_mut = Some(FutureCompatOverlapError {
                                 error: create_overlap_error(overlap),
-                                kind: FutureCompatOverlapErrorKind::Issue33140,
+                                kind: FutureCompatOverlapErrorKind::OrderDepTraitObjects,
                             });
                         }
                     }

compiler/rustc_ty_utils/src/ty.rs

@@ -243,37 +243,39 @@ fn param_env_reveal_all_normalized(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamE
     tcx.param_env(def_id).with_reveal_all_normalized(tcx)
 }
 
-/// If `def_id` is an issue 33140 hack impl, returns its self type; otherwise, returns `None`.
+/// If the given trait impl enables exploiting the former order dependence of trait objects,
+/// returns its self type; otherwise, returns `None`.
 ///
-/// See [`ty::ImplOverlapKind::Issue33140`] for more details.
-fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<EarlyBinder<Ty<'_>>> {
-    debug!("issue33140_self_ty({:?})", def_id);
-
-    let impl_ = tcx
-        .impl_trait_header(def_id)
-        .unwrap_or_else(|| bug!("issue33140_self_ty called on inherent impl {:?}", def_id));
+/// See [`ty::ImplOverlapKind::FutureCompatOrderDepTraitObjects`] for more details.
+#[instrument(level = "debug", skip(tcx))]
+fn self_ty_of_trait_impl_enabling_order_dep_trait_object_hack(
+    tcx: TyCtxt<'_>,
+    def_id: DefId,
+) -> Option<EarlyBinder<Ty<'_>>> {
+    let impl_ =
+        tcx.impl_trait_header(def_id).unwrap_or_else(|| bug!("called on inherent impl {def_id:?}"));
 
     let trait_ref = impl_.trait_ref.skip_binder();
-    debug!("issue33140_self_ty({:?}), trait-ref={:?}", def_id, trait_ref);
+    debug!(?trait_ref);
 
     let is_marker_like = impl_.polarity == ty::ImplPolarity::Positive
         && tcx.associated_item_def_ids(trait_ref.def_id).is_empty();
 
     // Check whether these impls would be ok for a marker trait.
     if !is_marker_like {
-        debug!("issue33140_self_ty - not marker-like!");
+        debug!("not marker-like!");
         return None;
     }
 
     // impl must be `impl Trait for dyn Marker1 + Marker2 + ...`
     if trait_ref.args.len() != 1 {
-        debug!("issue33140_self_ty - impl has args!");
+        debug!("impl has args!");
         return None;
     }
 
     let predicates = tcx.predicates_of(def_id);
     if predicates.parent.is_some() || !predicates.predicates.is_empty() {
-        debug!("issue33140_self_ty - impl has predicates {:?}!", predicates);
+        debug!(?predicates, "impl has predicates!");
         return None;
     }
 
@@ -284,10 +286,10 @@ fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<EarlyBinder<Ty<'
     };
 
     if self_ty_matches {
-        debug!("issue33140_self_ty - MATCHES!");
+        debug!("MATCHES!");
         Some(EarlyBinder::bind(self_ty))
     } else {
-        debug!("issue33140_self_ty - non-matching self type");
+        debug!("non-matching self type");
         None
     }
 }
@@ -351,7 +353,7 @@ pub(crate) fn provide(providers: &mut Providers) {
         adt_sized_constraint,
         param_env,
         param_env_reveal_all_normalized,
-        issue33140_self_ty,
+        self_ty_of_trait_impl_enabling_order_dep_trait_object_hack,
         defaultness,
         unsizing_params_for_adt,
         ..*providers