Auto merge of #120136 - matthiaskrgr:rollup-3zzb0z9, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - #117561 (Stabilize `slice_first_last_chunk`)
 - #117662 ([rustdoc] Allows links in headings)
 - #119815 (Format sources into the error message when loading codegen backends)
 - #119835 (Exhaustiveness: simplify empty pattern logic)
 - #119984 (Change return type of unstable `Waker::noop()` from `Waker` to `&Waker`.)
 - #120009 (never_patterns: typecheck never patterns)
 - #120122 (Don't add needs-triage to A-diagnostics)
 - #120126 (Suggest `.swap()` when encountering conflicting borrows from `mem::swap` on a slice)
 - #120134 (Restrict access to the private field of newtype indexes)

Failed merges:

 - #119968 (Remove unused/unnecessary features)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -26,6 +26,7 @@ use rustc_span::hygiene::DesugaringKind;
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{BytePos, Span, Symbol};
 use rustc_trait_selection::infer::InferCtxtExt;
+use rustc_trait_selection::traits::error_reporting::FindExprBySpan;
 use rustc_trait_selection::traits::ObligationCtxt;
 use std::iter;
 
@@ -1304,14 +1305,96 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         place: Place<'tcx>,
         borrowed_place: Place<'tcx>,
     ) {
-        if let ([ProjectionElem::Index(_)], [ProjectionElem::Index(_)]) =
-            (&place.projection[..], &borrowed_place.projection[..])
+        let tcx = self.infcx.tcx;
+        let hir = tcx.hir();
+
+        if let ([ProjectionElem::Index(index1)], [ProjectionElem::Index(index2)])
+        | (
+            [ProjectionElem::Deref, ProjectionElem::Index(index1)],
+            [ProjectionElem::Deref, ProjectionElem::Index(index2)],
+        ) = (&place.projection[..], &borrowed_place.projection[..])
         {
-            err.help(
-                "consider using `.split_at_mut(position)` or similar method to obtain \
-                     two mutable non-overlapping sub-slices",
-            )
-            .help("consider using `.swap(index_1, index_2)` to swap elements at the specified indices");
+            let mut note_default_suggestion = || {
+                err.help(
+                    "consider using `.split_at_mut(position)` or similar method to obtain \
+                         two mutable non-overlapping sub-slices",
+                )
+                .help("consider using `.swap(index_1, index_2)` to swap elements at the specified indices");
+            };
+
+            let Some(body_id) = tcx.hir_node(self.mir_hir_id()).body_id() else {
+                note_default_suggestion();
+                return;
+            };
+
+            let mut expr_finder =
+                FindExprBySpan::new(self.body.local_decls[*index1].source_info.span);
+            expr_finder.visit_expr(hir.body(body_id).value);
+            let Some(index1) = expr_finder.result else {
+                note_default_suggestion();
+                return;
+            };
+
+            expr_finder = FindExprBySpan::new(self.body.local_decls[*index2].source_info.span);
+            expr_finder.visit_expr(hir.body(body_id).value);
+            let Some(index2) = expr_finder.result else {
+                note_default_suggestion();
+                return;
+            };
+
+            let sm = tcx.sess.source_map();
+
+            let Ok(index1_str) = sm.span_to_snippet(index1.span) else {
+                note_default_suggestion();
+                return;
+            };
+
+            let Ok(index2_str) = sm.span_to_snippet(index2.span) else {
+                note_default_suggestion();
+                return;
+            };
+
+            let Some(object) = hir.parent_id_iter(index1.hir_id).find_map(|id| {
+                if let hir::Node::Expr(expr) = tcx.hir_node(id)
+                    && let hir::ExprKind::Index(obj, ..) = expr.kind
+                {
+                    Some(obj)
+                } else {
+                    None
+                }
+            }) else {
+                note_default_suggestion();
+                return;
+            };
+
+            let Ok(obj_str) = sm.span_to_snippet(object.span) else {
+                note_default_suggestion();
+                return;
+            };
+
+            let Some(swap_call) = hir.parent_id_iter(object.hir_id).find_map(|id| {
+                if let hir::Node::Expr(call) = tcx.hir_node(id)
+                    && let hir::ExprKind::Call(callee, ..) = call.kind
+                    && let hir::ExprKind::Path(qpath) = callee.kind
+                    && let hir::QPath::Resolved(None, res) = qpath
+                    && let hir::def::Res::Def(_, did) = res.res
+                    && tcx.is_diagnostic_item(sym::mem_swap, did)
+                {
+                    Some(call)
+                } else {
+                    None
+                }
+            }) else {
+                note_default_suggestion();
+                return;
+            };
+
+            err.span_suggestion(
+                swap_call.span,
+                "use `.swap()` to swap elements at the specified indices instead",
+                format!("{obj_str}.swap({index1_str}, {index2_str})"),
+                Applicability::MachineApplicable,
+            );
         }
     }
 

compiler/rustc_codegen_cranelift/Cargo.lock

@@ -246,12 +246,12 @@ checksum = "9cdc71e17332e86d2e1d38c1f99edcb6288ee11b815fb1a4b049eaa2114d369b"
 
 [[package]]
 name = "libloading"
-version = "0.7.4"
+version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b67380fd3b2fbe7527a606e18729d21c6f3951633d0500574c4dc22d2d638b9f"
+checksum = "c571b676ddfc9a8c12f1f3d3085a7b163966a8fd8098a90640953ce5f6170161"
 dependencies = [
  "cfg-if",
- "winapi",
+ "windows-sys",
 ]
 
 [[package]]

compiler/rustc_codegen_cranelift/Cargo.toml

@@ -19,7 +19,7 @@ gimli = { version = "0.28", default-features = false, features = ["write"]}
 object = { version = "0.32", default-features = false, features = ["std", "read_core", "write", "archive", "coff", "elf", "macho", "pe"] }
 
 indexmap = "2.0.0"
-libloading = { version = "0.7.3", optional = true }
+libloading = { version = "0.8.0", optional = true }
 smallvec = "1.8.1"
 
 [patch.crates-io]

compiler/rustc_hir_typeck/src/pat.rs

@@ -178,8 +178,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let ty = match pat.kind {
             PatKind::Wild | PatKind::Err(_) => expected,
-            // FIXME(never_patterns): check the type is uninhabited. If that is not possible within
-            // typeck, do that in a later phase.
+            // We allow any type here; we ensure that the type is uninhabited during match checking.
             PatKind::Never => expected,
             PatKind::Lit(lt) => self.check_pat_lit(pat.span, lt, expected, ti),
             PatKind::Range(lhs, rhs, _) => self.check_pat_range(pat.span, lhs, rhs, expected, ti),

compiler/rustc_index_macros/src/newtype.rs

@@ -104,7 +104,7 @@ impl Parse for Newtype {
                 #gate_rustc_only
                 impl<E: ::rustc_serialize::Encoder> ::rustc_serialize::Encodable<E> for #name {
                     fn encode(&self, e: &mut E) {
-                        e.emit_u32(self.private);
+                        e.emit_u32(self.as_u32());
                     }
                 }
             }
@@ -164,7 +164,7 @@ impl Parse for Newtype {
                         #[inline]
                         fn eq(l: &Option<Self>, r: &Option<Self>) -> bool {
                             if #max_val < u32::MAX {
-                                l.map(|i| i.private).unwrap_or(#max_val+1) == r.map(|i| i.private).unwrap_or(#max_val+1)
+                                l.map(|i| i.as_u32()).unwrap_or(#max_val+1) == r.map(|i| i.as_u32()).unwrap_or(#max_val+1)
                             } else {
                                 match (l, r) {
                                     (Some(l), Some(r)) => r == l,
@@ -188,7 +188,7 @@ impl Parse for Newtype {
             #[cfg_attr(#gate_rustc_only_cfg, rustc_layout_scalar_valid_range_end(#max))]
             #[cfg_attr(#gate_rustc_only_cfg, rustc_pass_by_value)]
             #vis struct #name {
-                private: u32,
+                private_use_as_methods_instead: u32,
             }
 
             #(#consts)*
@@ -238,7 +238,7 @@ impl Parse for Newtype {
                 /// Prefer using `from_u32`.
                 #[inline]
                 #vis const unsafe fn from_u32_unchecked(value: u32) -> Self {
-                    Self { private: value }
+                    Self { private_use_as_methods_instead: value }
                 }
 
                 /// Extracts the value of this index as a `usize`.
@@ -250,7 +250,7 @@ impl Parse for Newtype {
                 /// Extracts the value of this index as a `u32`.
                 #[inline]
                 #vis const fn as_u32(self) -> u32 {
-                    self.private
+                    self.private_use_as_methods_instead
                 }
 
                 /// Extracts the value of this index as a `usize`.

compiler/rustc_interface/Cargo.toml

@@ -5,7 +5,7 @@ edition = "2021"
 
 [dependencies]
 # tidy-alphabetical-start
-libloading = "0.7.1"
+libloading = "0.8.0"
 rustc-rayon = { version = "0.5.0", optional = true }
 rustc-rayon-core = { version = "0.5.0", optional = true }
 rustc_ast = { path = "../rustc_ast" }

compiler/rustc_interface/src/lib.rs

@@ -1,9 +1,10 @@
 #![feature(box_patterns)]
 #![feature(decl_macro)]
+#![feature(error_iter)]
 #![feature(internal_output_capture)]
-#![feature(thread_spawn_unchecked)]
 #![feature(lazy_cell)]
 #![feature(let_chains)]
+#![feature(thread_spawn_unchecked)]
 #![feature(try_blocks)]
 #![recursion_limit = "256"]
 #![deny(rustc::untranslatable_diagnostic)]

compiler/rustc_interface/src/util.rs

@@ -162,15 +162,21 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce() -> R + Send, R: Send>(
 }
 
 fn load_backend_from_dylib(early_dcx: &EarlyDiagCtxt, path: &Path) -> MakeBackendFn {
+    fn format_err(e: &(dyn std::error::Error + 'static)) -> String {
+        e.sources().map(|e| format!(": {e}")).collect()
+    }
     let lib = unsafe { Library::new(path) }.unwrap_or_else(|err| {
-        let err = format!("couldn't load codegen backend {path:?}: {err}");
+        let err = format!("couldn't load codegen backend {path:?}{}", format_err(&err));
         early_dcx.early_fatal(err);
     });
 
     let backend_sym = unsafe { lib.get::<MakeBackendFn>(b"__rustc_codegen_backend") }
         .unwrap_or_else(|e| {
-            let err = format!("couldn't load codegen backend: {e}");
-            early_dcx.early_fatal(err);
+            let e = format!(
+                "`__rustc_codegen_backend` symbol lookup in the codegen backend failed{}",
+                format_err(&e)
+            );
+            early_dcx.early_fatal(e);
         });
 
     // Intentionally leak the dynamic library. We can't ever unload it

compiler/rustc_metadata/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 bitflags = "2.4.1"
-libloading = "0.7.1"
+libloading = "0.8.0"
 odht = { version = "0.3.1", features = ["nightly"] }
 rustc_ast = { path = "../rustc_ast" }
 rustc_attr = { path = "../rustc_attr" }

compiler/rustc_mir_build/messages.ftl

@@ -234,6 +234,11 @@ mir_build_mutation_of_layout_constrained_field_requires_unsafe_unsafe_op_in_unsa
 
 mir_build_non_const_path = runtime values cannot be referenced in patterns
 
+mir_build_non_empty_never_pattern =
+    mismatched types
+    .label = a never pattern must be used on an uninhabited type
+    .note = the matched value is of type `{$ty}`
+
 mir_build_non_exhaustive_match_all_arms_guarded =
     match arms with guards don't count towards exhaustivity
 

compiler/rustc_mir_build/src/errors.rs

@@ -788,6 +788,16 @@ pub struct FloatPattern;
 #[diag(mir_build_pointer_pattern)]
 pub struct PointerPattern;
 
+#[derive(Diagnostic)]
+#[diag(mir_build_non_empty_never_pattern)]
+#[note]
+pub struct NonEmptyNeverPattern<'tcx> {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    pub ty: Ty<'tcx>,
+}
+
 #[derive(LintDiagnostic)]
 #[diag(mir_build_indirect_structural_match)]
 #[note(mir_build_type_not_structural_tip)]

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -276,10 +276,13 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
         } else {
             // Check the pattern for some things unrelated to exhaustiveness.
             let refutable = if cx.refutable { Refutable } else { Irrefutable };
+            let mut err = Ok(());
             pat.walk_always(|pat| {
                 check_borrow_conflicts_in_at_patterns(self, pat);
                 check_for_bindings_named_same_as_variants(self, pat, refutable);
+                err = err.and(check_never_pattern(cx, pat));
             });
+            err?;
             Ok(cx.pattern_arena.alloc(cx.lower_pat(pat)))
         }
     }
@@ -289,7 +292,8 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
     fn is_known_valid_scrutinee(&self, scrutinee: &Expr<'tcx>) -> bool {
         use ExprKind::*;
         match &scrutinee.kind {
-            // Both pointers and references can validly point to a place with invalid data.
+            // Pointers can validly point to a place with invalid data. It is undecided whether
+            // references can too, so we conservatively assume they can.
             Deref { .. } => false,
             // Inherit validity of the parent place, unless the parent is an union.
             Field { lhs, .. } => {
@@ -811,6 +815,19 @@ fn check_for_bindings_named_same_as_variants(
     }
 }
 
+/// Check that never patterns are only used on inhabited types.
+fn check_never_pattern<'tcx>(
+    cx: &MatchCheckCtxt<'_, 'tcx>,
+    pat: &Pat<'tcx>,
+) -> Result<(), ErrorGuaranteed> {
+    if let PatKind::Never = pat.kind {
+        if !cx.is_uninhabited(pat.ty) {
+            return Err(cx.tcx.dcx().emit_err(NonEmptyNeverPattern { span: pat.span, ty: pat.ty }));
+        }
+    }
+    Ok(())
+}
+
 fn report_irrefutable_let_patterns(
     tcx: TyCtxt<'_>,
     id: HirId,

compiler/rustc_pattern_analysis/src/constructor.rs

@@ -861,12 +861,14 @@ impl<Cx: TypeCx> ConstructorSet<Cx> {
     /// any) are missing; 2/ split constructors to handle non-trivial intersections e.g. on ranges
     /// or slices. This can get subtle; see [`SplitConstructorSet`] for details of this operation
     /// and its invariants.
-    #[instrument(level = "debug", skip(self, pcx, ctors), ret)]
+    #[instrument(level = "debug", skip(self, ctors), ret)]
     pub(crate) fn split<'a>(
         &self,
-        pcx: &PlaceCtxt<'a, Cx>,
         ctors: impl Iterator<Item = &'a Constructor<Cx>> + Clone,
-    ) -> SplitConstructorSet<Cx> {
+    ) -> SplitConstructorSet<Cx>
+    where
+        Cx: 'a,
+    {
         let mut present: SmallVec<[_; 1]> = SmallVec::new();
         // Empty constructors found missing.
         let mut missing_empty = Vec::new();
@@ -1006,17 +1008,6 @@ impl<Cx: TypeCx> ConstructorSet<Cx> {
             }
         }
 
-        // We have now grouped all the constructors into 3 buckets: present, missing, missing_empty.
-        // In the absence of the `exhaustive_patterns` feature however, we don't count nested empty
-        // types as empty. Only non-nested `!` or `enum Foo {}` are considered empty.
-        if !pcx.mcx.tycx.is_exhaustive_patterns_feature_on()
-            && !(pcx.is_scrutinee && matches!(self, Self::NoConstructors))
-        {
-            // Treat all missing constructors as nonempty.
-            // This clears `missing_empty`.
-            missing.append(&mut missing_empty);
-        }
-
         SplitConstructorSet { present, missing, missing_empty }
     }
 }

compiler/rustc_pattern_analysis/src/lints.rs

@@ -56,7 +56,7 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
     ) -> Result<SplitConstructorSet<'p, 'tcx>, ErrorGuaranteed> {
         let column_ctors = self.patterns.iter().map(|p| p.ctor());
         let ctors_for_ty = &pcx.ctors_for_ty()?;
-        Ok(ctors_for_ty.split(pcx, column_ctors))
+        Ok(ctors_for_ty.split(column_ctors))
     }
 
     /// Does specialization: given a constructor, this takes the patterns from the column that match

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -737,15 +737,13 @@ pub(crate) struct PlaceCtxt<'a, Cx: TypeCx> {
     pub(crate) mcx: MatchCtxt<'a, Cx>,
     /// Type of the place under investigation.
     pub(crate) ty: Cx::Ty,
-    /// Whether the place is the original scrutinee place, as opposed to a subplace of it.
-    pub(crate) is_scrutinee: bool,
 }
 
 impl<'a, Cx: TypeCx> PlaceCtxt<'a, Cx> {
     /// A `PlaceCtxt` when code other than `is_useful` needs one.
     #[cfg_attr(not(feature = "rustc"), allow(dead_code))]
     pub(crate) fn new_dummy(mcx: MatchCtxt<'a, Cx>, ty: Cx::Ty) -> Self {
-        PlaceCtxt { mcx, ty, is_scrutinee: false }
+        PlaceCtxt { mcx, ty }
     }
 
     pub(crate) fn ctor_arity(&self, ctor: &Constructor<Cx>) -> usize {
@@ -768,9 +766,6 @@ impl<'a, Cx: TypeCx> PlaceCtxt<'a, Cx> {
 pub enum ValidityConstraint {
     ValidOnly,
     MaybeInvalid,
-    /// Option for backwards compatibility: the place is not known to be valid but we allow omitting
-    /// `useful && !reachable` arms anyway.
-    MaybeInvalidButAllowOmittingArms,
 }
 
 impl ValidityConstraint {
@@ -778,20 +773,9 @@ impl ValidityConstraint {
         if is_valid_only { ValidOnly } else { MaybeInvalid }
     }
 
-    fn allow_omitting_side_effecting_arms(self) -> Self {
-        match self {
-            MaybeInvalid | MaybeInvalidButAllowOmittingArms => MaybeInvalidButAllowOmittingArms,
-            // There are no side-effecting empty arms here, nothing to do.
-            ValidOnly => ValidOnly,
-        }
-    }
-
     fn is_known_valid(self) -> bool {
         matches!(self, ValidOnly)
     }
-    fn allows_omitting_empty_arms(self) -> bool {
-        matches!(self, ValidOnly | MaybeInvalidButAllowOmittingArms)
-    }
 
     /// If the place has validity given by `self` and we read that the value at the place has
     /// constructor `ctor`, this computes what we can assume about the validity of the constructor
@@ -814,7 +798,7 @@ impl fmt::Display for ValidityConstraint {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let s = match self {
             ValidOnly => "✓",
-            MaybeInvalid | MaybeInvalidButAllowOmittingArms => "?",
+            MaybeInvalid => "?",
         };
         write!(f, "{s}")
     }
@@ -1447,41 +1431,44 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
     };
 
     debug!("ty: {ty:?}");
-    let pcx = &PlaceCtxt { mcx, ty, is_scrutinee: is_top_level };
+    let pcx = &PlaceCtxt { mcx, ty };
+    let ctors_for_ty = pcx.ctors_for_ty()?;
 
     // Whether the place/column we are inspecting is known to contain valid data.
     let place_validity = matrix.place_validity[0];
-    // For backwards compability we allow omitting some empty arms that we ideally shouldn't.
-    let place_validity = place_validity.allow_omitting_side_effecting_arms();
+    // We treat match scrutinees of type `!` or `EmptyEnum` differently.
+    let is_toplevel_exception =
+        is_top_level && matches!(ctors_for_ty, ConstructorSet::NoConstructors);
+    // Whether empty patterns can be omitted for exhaustiveness.
+    let can_omit_empty_arms = is_toplevel_exception || mcx.tycx.is_exhaustive_patterns_feature_on();
+    // Whether empty patterns are counted as useful or not.
+    let empty_arms_are_unreachable = place_validity.is_known_valid() && can_omit_empty_arms;
 
     // Analyze the constructors present in this column.
     let ctors = matrix.heads().map(|p| p.ctor());
-    let ctors_for_ty = pcx.ctors_for_ty()?;
-    let is_integers = matches!(ctors_for_ty, ConstructorSet::Integers { .. }); // For diagnostics.
-    let split_set = ctors_for_ty.split(pcx, ctors);
+    let mut split_set = ctors_for_ty.split(ctors);
     let all_missing = split_set.present.is_empty();
-
     // Build the set of constructors we will specialize with. It must cover the whole type.
+    // We need to iterate over a full set of constructors, so we add `Missing` to represent the
+    // missing ones. This is explained under "Constructor Splitting" at the top of this file.
     let mut split_ctors = split_set.present;
-    if !split_set.missing.is_empty() {
-        // We need to iterate over a full set of constructors, so we add `Missing` to represent the
-        // missing ones. This is explained under "Constructor Splitting" at the top of this file.
-        split_ctors.push(Constructor::Missing);
-    } else if !split_set.missing_empty.is_empty() && !place_validity.is_known_valid() {
-        // The missing empty constructors are reachable if the place can contain invalid data.
+    if !(split_set.missing.is_empty()
+        && (split_set.missing_empty.is_empty() || empty_arms_are_unreachable))
+    {
         split_ctors.push(Constructor::Missing);
     }
 
     // Decide what constructors to report.
+    let is_integers = matches!(ctors_for_ty, ConstructorSet::Integers { .. });
     let always_report_all = is_top_level && !is_integers;
     // Whether we should report "Enum::A and Enum::C are missing" or "_ is missing".
     let report_individual_missing_ctors = always_report_all || !all_missing;
     // Which constructors are considered missing. We ensure that `!missing_ctors.is_empty() =>
-    // split_ctors.contains(Missing)`. The converse usually holds except in the
-    // `MaybeInvalidButAllowOmittingArms` backwards-compatibility case.
+    // split_ctors.contains(Missing)`. The converse usually holds except when
+    // `!place_validity.is_known_valid()`.
     let mut missing_ctors = split_set.missing;
-    if !place_validity.allows_omitting_empty_arms() {
-        missing_ctors.extend(split_set.missing_empty);
+    if !can_omit_empty_arms {
+        missing_ctors.append(&mut split_set.missing_empty);
     }
 
     let mut ret = WitnessMatrix::empty();

compiler/rustc_serialize/src/lib.rs

@@ -16,7 +16,6 @@
 #![feature(min_specialization)]
 #![feature(never_type)]
 #![feature(ptr_sub_ptr)]
-#![feature(slice_first_last_chunk)]
 #![cfg_attr(test, feature(test))]
 #![allow(rustc::internal)]
 #![deny(rustc::untranslatable_diagnostic)]

compiler/rustc_type_ir/src/lib.rs

@@ -327,21 +327,21 @@ impl UniverseIndex {
     /// name the region `'a`, but that region was not nameable from
     /// `U` because it was not in scope there.
     pub fn next_universe(self) -> UniverseIndex {
-        UniverseIndex::from_u32(self.private.checked_add(1).unwrap())
+        UniverseIndex::from_u32(self.as_u32().checked_add(1).unwrap())
     }
 
     /// Returns `true` if `self` can name a name from `other` -- in other words,
     /// if the set of names in `self` is a superset of those in
     /// `other` (`self >= other`).
     pub fn can_name(self, other: UniverseIndex) -> bool {
-        self.private >= other.private
+        self >= other
     }
 
     /// Returns `true` if `self` cannot name some names from `other` -- in other
     /// words, if the set of names in `self` is a strict subset of
     /// those in `other` (`self < other`).
     pub fn cannot_name(self, other: UniverseIndex) -> bool {
-        self.private < other.private
+        self < other
     }
 }