get rid of nontrivial_structural_match lint and custom_eq const qualif

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -20,7 +20,7 @@ use std::mem;
 use std::ops::{ControlFlow, Deref};
 
 use super::ops::{self, NonConstOp, Status};
-use super::qualifs::{self, CustomEq, HasMutInterior, NeedsDrop, NeedsNonConstDrop};
+use super::qualifs::{self, HasMutInterior, NeedsDrop, NeedsNonConstDrop};
 use super::resolver::FlowSensitiveAnalysis;
 use super::{ConstCx, Qualif};
 use crate::const_eval::is_unstable_const_fn;
@@ -149,37 +149,10 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
 
         let return_loc = ccx.body.terminator_loc(return_block);
 
-        let custom_eq = match ccx.const_kind() {
-            // We don't care whether a `const fn` returns a value that is not structurally
-            // matchable. Functions calls are opaque and always use type-based qualification, so
-            // this value should never be used.
-            hir::ConstContext::ConstFn => true,
-
-            // If we know that all values of the return type are structurally matchable, there's no
-            // need to run dataflow.
-            // Opaque types do not participate in const generics or pattern matching, so we can safely count them out.
-            _ if ccx.body.return_ty().has_opaque_types()
-                || !CustomEq::in_any_value_of_ty(ccx, ccx.body.return_ty()) =>
-            {
-                false
-            }
-
-            hir::ConstContext::Const { .. } | hir::ConstContext::Static(_) => {
-                let mut cursor = FlowSensitiveAnalysis::new(CustomEq, ccx)
-                    .into_engine(ccx.tcx, ccx.body)
-                    .iterate_to_fixpoint()
-                    .into_results_cursor(ccx.body);
-
-                cursor.seek_after_primary_effect(return_loc);
-                cursor.get().contains(RETURN_PLACE)
-            }
-        };
-
         ConstQualifs {
             needs_drop: self.needs_drop(ccx, RETURN_PLACE, return_loc),
             needs_non_const_drop: self.needs_non_const_drop(ccx, RETURN_PLACE, return_loc),
             has_mut_interior: self.has_mut_interior(ccx, RETURN_PLACE, return_loc),
-            custom_eq,
             tainted_by_errors,
         }
     }

compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs

@@ -10,7 +10,7 @@ use rustc_middle::mir::*;
 use rustc_middle::traits::BuiltinImplSource;
 use rustc_middle::ty::{self, AdtDef, GenericArgsRef, Ty};
 use rustc_trait_selection::traits::{
-    self, ImplSource, Obligation, ObligationCause, ObligationCtxt, SelectionContext,
+    ImplSource, Obligation, ObligationCause, ObligationCtxt, SelectionContext,
 };
 
 use super::ConstCx;
@@ -24,7 +24,6 @@ pub fn in_any_value_of_ty<'tcx>(
         has_mut_interior: HasMutInterior::in_any_value_of_ty(cx, ty),
         needs_drop: NeedsDrop::in_any_value_of_ty(cx, ty),
         needs_non_const_drop: NeedsNonConstDrop::in_any_value_of_ty(cx, ty),
-        custom_eq: CustomEq::in_any_value_of_ty(cx, ty),
         tainted_by_errors,
     }
 }
@@ -213,35 +212,6 @@ impl Qualif for NeedsNonConstDrop {
     }
 }
 
-/// A constant that cannot be used as part of a pattern in a `match` expression.
-pub struct CustomEq;
-
-impl Qualif for CustomEq {
-    const ANALYSIS_NAME: &'static str = "flow_custom_eq";
-
-    fn in_qualifs(qualifs: &ConstQualifs) -> bool {
-        qualifs.custom_eq
-    }
-
-    fn in_any_value_of_ty<'tcx>(cx: &ConstCx<'_, 'tcx>, ty: Ty<'tcx>) -> bool {
-        // If *any* component of a composite data type does not implement `Structural{Partial,}Eq`,
-        // we know that at least some values of that type are not structural-match. I say "some"
-        // because that component may be part of an enum variant (e.g.,
-        // `Option::<NonStructuralMatchTy>::Some`), in which case some values of this type may be
-        // structural-match (`Option::None`).
-        traits::search_for_structural_match_violation(cx.body.span, cx.tcx, ty).is_some()
-    }
-
-    fn in_adt_inherently<'tcx>(
-        cx: &ConstCx<'_, 'tcx>,
-        def: AdtDef<'tcx>,
-        args: GenericArgsRef<'tcx>,
-    ) -> bool {
-        let ty = Ty::new_adt(cx.tcx, def, args);
-        !ty.is_structural_eq_shallow(cx.tcx)
-    }
-}
-
 // FIXME: Use `mir::visit::Visitor` for the `in_*` functions if/when it supports early return.
 
 /// Returns `true` if this `Rvalue` contains qualif `Q`.

compiler/rustc_lint/src/lib.rs

@@ -520,6 +520,11 @@ fn register_builtins(store: &mut LintStore) {
         "illegal_floating_point_literal_pattern",
         "no longer a warning, float patterns behave the same as `==`",
     );
+    store.register_removed(
+        "nontrivial_structural_match",
+        "no longer needed, see RFC #3535 \
+         <https://rust-lang.github.io/rfcs/3535-constants-in-patterns.html> for more information",
+    );
 }
 
 fn register_internals(store: &mut LintStore) {

compiler/rustc_lint_defs/src/builtin.rs

@@ -3,6 +3,9 @@
 //! These are the built-in lints that are emitted direct in the main
 //! compiler code, rather than using their own custom pass. Those
 //! lints are all available in `rustc_lint::builtin`.
+//!
+//! When removing a lint, make sure to also add a call to `register_removed` in
+//! compiler/rustc_lint/src/lib.rs.
 
 use crate::{declare_lint, declare_lint_pass, FutureIncompatibilityReason};
 use rustc_span::edition::Edition;
@@ -66,7 +69,6 @@ declare_lint_pass! {
         MUST_NOT_SUSPEND,
         NAMED_ARGUMENTS_USED_POSITIONALLY,
         NON_EXHAUSTIVE_OMITTED_PATTERNS,
-        NONTRIVIAL_STRUCTURAL_MATCH,
         ORDER_DEPENDENT_TRAIT_OBJECTS,
         OVERLAPPING_RANGE_ENDPOINTS,
         PATTERNS_IN_FNS_WITHOUT_BODY,
@@ -2341,45 +2343,6 @@ declare_lint! {
     };
 }
 
-declare_lint! {
-    /// The `nontrivial_structural_match` lint detects constants that are used in patterns,
-    /// whose type is not structural-match and whose initializer body actually uses values
-    /// that are not structural-match. So `Option<NotStructuralMatch>` is ok if the constant
-    /// is just `None`.
-    ///
-    /// ### Example
-    ///
-    /// ```rust,compile_fail
-    /// #![deny(nontrivial_structural_match)]
-    ///
-    /// #[derive(Copy, Clone, Debug)]
-    /// struct NoDerive(u32);
-    /// impl PartialEq for NoDerive { fn eq(&self, _: &Self) -> bool { false } }
-    /// impl Eq for NoDerive { }
-    /// fn main() {
-    ///     const INDEX: Option<NoDerive> = [None, Some(NoDerive(10))][0];
-    ///     match None { Some(_) => panic!("whoops"), INDEX => dbg!(INDEX), };
-    /// }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// Previous versions of Rust accepted constants in patterns, even if those constants' types
-    /// did not have `PartialEq` derived. Thus the compiler falls back to runtime execution of
-    /// `PartialEq`, which can report that two constants are not equal even if they are
-    /// bit-equivalent.
-    pub NONTRIVIAL_STRUCTURAL_MATCH,
-    Warn,
-    "constant used in pattern of non-structural-match type and the constant's initializer \
-    expression contains values of non-structural-match types",
-    @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
-        reference: "issue #73448 <https://github.com/rust-lang/rust/issues/73448>",
-    };
-}
-
 declare_lint! {
     /// The `const_patterns_without_partial_eq` lint detects constants that are used in patterns,
     /// whose type does not implement `PartialEq`.

compiler/rustc_middle/src/mir/query.rs

@@ -189,7 +189,7 @@ pub struct BorrowCheckResult<'tcx> {
 
 /// The result of the `mir_const_qualif` query.
 ///
-/// Each field (except `error_occurred`) corresponds to an implementer of the `Qualif` trait in
+/// Each field (except `tainted_by_errors`) corresponds to an implementer of the `Qualif` trait in
 /// `rustc_const_eval/src/transform/check_consts/qualifs.rs`. See that file for more information on each
 /// `Qualif`.
 #[derive(Clone, Copy, Debug, Default, TyEncodable, TyDecodable, HashStable)]
@@ -197,7 +197,6 @@ pub struct ConstQualifs {
     pub has_mut_interior: bool,
     pub needs_drop: bool,
     pub needs_non_const_drop: bool,
-    pub custom_eq: bool,
     pub tainted_by_errors: Option<ErrorGuaranteed>,
 }
 

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

@@ -1,6 +1,5 @@
 use rustc_apfloat::Float;
 use rustc_hir as hir;
-use rustc_hir::def_id::DefId;
 use rustc_index::Idx;
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::Obligation;
@@ -17,8 +16,8 @@ use std::cell::Cell;
 
 use super::PatCtxt;
 use crate::errors::{
-    IndirectStructuralMatch, InvalidPattern, NaNPattern, NonPartialEqMatch,
+    IndirectStructuralMatch, InvalidPattern, NaNPattern, NonPartialEqMatch, PointerPattern,
-    NontrivialStructuralMatch, PointerPattern, TypeNotStructural, UnionPattern, UnsizedPattern,
+    TypeNotStructural, UnionPattern, UnsizedPattern,
 };
 
 impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
@@ -33,11 +32,10 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         cv: mir::Const<'tcx>,
         id: hir::HirId,
         span: Span,
-        check_body_for_struct_match_violation: Option<DefId>,
     ) -> Box<Pat<'tcx>> {
         let infcx = self.tcx.infer_ctxt().build();
         let mut convert = ConstToPat::new(self, id, span, infcx);
-        convert.to_pat(cv, check_body_for_struct_match_violation)
+        convert.to_pat(cv)
     }
 }
 
@@ -103,11 +101,7 @@ impl<'tcx> ConstToPat<'tcx> {
         ty.is_structural_eq_shallow(self.infcx.tcx)
     }
 
-    fn to_pat(
+    fn to_pat(&mut self, cv: mir::Const<'tcx>) -> Box<Pat<'tcx>> {
-        &mut self,
-        cv: mir::Const<'tcx>,
-        check_body_for_struct_match_violation: Option<DefId>,
-    ) -> Box<Pat<'tcx>> {
         trace!(self.treat_byte_string_as_slice);
         // This method is just a wrapper handling a validity check; the heavy lifting is
         // performed by the recursive `recur` method, which is not meant to be
@@ -116,14 +110,6 @@ impl<'tcx> ConstToPat<'tcx> {
         // once indirect_structural_match is a full fledged error, this
         // level of indirection can be eliminated
 
-        let mir_structural_match_violation = check_body_for_struct_match_violation.map(|def_id| {
-            // `mir_const_qualif` must be called with the `DefId` of the item where the const is
-            // defined, not where it is declared. The difference is significant for associated
-            // constants.
-            self.tcx().mir_const_qualif(def_id).custom_eq
-        });
-        debug!(?check_body_for_struct_match_violation, ?mir_structural_match_violation);
-
         let have_valtree =
             matches!(cv, mir::Const::Ty(c) if matches!(c.kind(), ty::ConstKind::Value(_)));
         let inlined_const_as_pat = match cv {
@@ -137,15 +123,15 @@ impl<'tcx> ConstToPat<'tcx> {
                 | ty::ConstKind::Expr(_) => {
                     span_bug!(self.span, "unexpected const in `to_pat`: {:?}", c.kind())
                 }
-                ty::ConstKind::Value(valtree) => self
+                ty::ConstKind::Value(valtree) => {
-                    .recur(valtree, cv.ty(), mir_structural_match_violation.unwrap_or(false))
+                    self.recur(valtree, cv.ty()).unwrap_or_else(|_: FallbackToOpaqueConst| {
-                    .unwrap_or_else(|_: FallbackToOpaqueConst| {
                         Box::new(Pat {
                             span: self.span,
                             ty: cv.ty(),
                             kind: PatKind::Constant { value: cv },
                         })
-                    }),
+                    })
+                }
             },
             mir::Const::Unevaluated(_, _) => {
                 span_bug!(self.span, "unevaluated const in `to_pat`: {cv:?}")
@@ -160,7 +146,12 @@ impl<'tcx> ConstToPat<'tcx> {
         if self.saw_const_match_error.get().is_none() {
             // If we were able to successfully convert the const to some pat (possibly with some
             // lints, but no errors), double-check that all types in the const implement
-            // `Structural` and `PartialEq`.
+            // `PartialEq`. Even if we have a valtree, we may have found something
+            // in there with non-structural-equality, meaning we match using `PartialEq`
+            // and we hence have to check that that impl exists.
+            // This is all messy but not worth cleaning up: at some point we'll emit
+            // a hard error when we don't have a valtree or when we find something in
+            // the valtree that is not structural; then this can all be made a lot simpler.
 
             let structural =
                 traits::search_for_structural_match_violation(self.span, self.tcx(), cv.ty());
@@ -170,19 +161,12 @@ impl<'tcx> ConstToPat<'tcx> {
                 structural
             );
 
-            // This can occur because const qualification treats all associated constants as
-            // opaque, whereas `search_for_structural_match_violation` tries to monomorphize them
-            // before it runs.
-            //
-            // FIXME(#73448): Find a way to bring const qualification into parity with
-            // `search_for_structural_match_violation`.
-            if structural.is_none() && mir_structural_match_violation.unwrap_or(false) {
-                warn!("MIR const-checker found novel structural match violation. See #73448.");
-                return inlined_const_as_pat;
-            }
-
             if let Some(non_sm_ty) = structural {
                 if !self.type_has_partial_eq_impl(cv.ty()) {
+                    // This is reachable and important even if we have a valtree: there might be
+                    // non-structural things in a valtree, in which case we fall back to `PartialEq`
+                    // comparison, in which case we better make sure the trait is implemented for
+                    // each inner type (and not just for the surrounding type).
                     let e = if let ty::Adt(def, ..) = non_sm_ty.kind() {
                         if def.is_union() {
                             let err = UnionPattern { span: self.span };
@@ -201,35 +185,18 @@ impl<'tcx> ConstToPat<'tcx> {
                     // We errored. Signal that in the pattern, so that follow up errors can be silenced.
                     let kind = PatKind::Error(e);
                     return Box::new(Pat { span: self.span, ty: cv.ty(), kind });
-                } else if let ty::Adt(..) = cv.ty().kind()
+                } else if !have_valtree {
-                    && matches!(cv, mir::Const::Val(..))
+                    // Not being structural prevented us from constructing a valtree,
-                {
+                    // so this is definitely a case we want to reject.
-                    // This branch is only entered when the current `cv` is `mir::Const::Val`.
-                    // This is because `mir::Const::ty` has already been handled by `Self::recur`
-                    // and the invalid types may be ignored.
                     let err = TypeNotStructural { span: self.span, non_sm_ty };
                     let e = self.tcx().dcx().emit_err(err);
                     let kind = PatKind::Error(e);
                     return Box::new(Pat { span: self.span, ty: cv.ty(), kind });
-                } else if !self.saw_const_match_lint.get() {
+                } else {
-                    if let Some(mir_structural_match_violation) = mir_structural_match_violation {
+                    // This could be a violation in an inactive enum variant.
-                        match non_sm_ty.kind() {
+                    // Since we have a valtree, we trust that we have traversed the full valtree and
-                            ty::Adt(..) if mir_structural_match_violation => {
+                    // complained about structural match violations there, so we don't
-                                self.tcx().emit_node_span_lint(
+                    // have to check anything any more.
-                                    lint::builtin::INDIRECT_STRUCTURAL_MATCH,
-                                    self.id,
-                                    self.span,
-                                    IndirectStructuralMatch { non_sm_ty },
-                                );
-                            }
-                            _ => {
-                                debug!(
-                                    "`search_for_structural_match_violation` found one, but `CustomEq` was \
-                                  not in the qualifs for that `const`"
-                                );
-                            }
-                        }
-                    }
                 }
             } else if !have_valtree && !self.saw_const_match_lint.get() {
                 // The only way valtree construction can fail without the structural match
@@ -299,7 +266,7 @@ impl<'tcx> ConstToPat<'tcx> {
                 let field = FieldIdx::new(idx);
                 // Patterns can only use monomorphic types.
                 let ty = self.tcx().normalize_erasing_regions(self.param_env, ty);
-                Ok(FieldPat { field, pattern: self.recur(val, ty, false)? })
+                Ok(FieldPat { field, pattern: self.recur(val, ty)? })
             })
             .collect()
     }
@@ -310,7 +277,6 @@ impl<'tcx> ConstToPat<'tcx> {
         &self,
         cv: ValTree<'tcx>,
         ty: Ty<'tcx>,
-        mir_structural_match_violation: bool,
     ) -> Result<Box<Pat<'tcx>>, FallbackToOpaqueConst> {
         let id = self.id;
         let span = self.span;
@@ -395,7 +361,7 @@ impl<'tcx> ConstToPat<'tcx> {
                 prefix: cv
                     .unwrap_branch()
                     .iter()
-                    .map(|val| self.recur(*val, *elem_ty, false))
+                    .map(|val| self.recur(*val, *elem_ty))
                     .collect::<Result<_, _>>()?,
                 slice: None,
                 suffix: Box::new([]),
@@ -404,7 +370,7 @@ impl<'tcx> ConstToPat<'tcx> {
                 prefix: cv
                     .unwrap_branch()
                     .iter()
-                    .map(|val| self.recur(*val, *elem_ty, false))
+                    .map(|val| self.recur(*val, *elem_ty))
                     .collect::<Result<_, _>>()?,
                 slice: None,
                 suffix: Box::new([]),
@@ -471,7 +437,7 @@ impl<'tcx> ConstToPat<'tcx> {
                             _ => *pointee_ty,
                         };
                         // References have the same valtree representation as their pointee.
-                        let subpattern = self.recur(cv, pointee_ty, false)?;
+                        let subpattern = self.recur(cv, pointee_ty)?;
                         self.behind_reference.set(old);
                         PatKind::Deref { subpattern }
                     }
@@ -512,25 +478,6 @@ impl<'tcx> ConstToPat<'tcx> {
             }
         };
 
-        if self.saw_const_match_error.get().is_none()
-            && !self.saw_const_match_lint.get()
-            && mir_structural_match_violation
-            // FIXME(#73448): Find a way to bring const qualification into parity with
-            // `search_for_structural_match_violation` and then remove this condition.
-
-            // Obtain the actual type that isn't annotated. If we just looked at `cv.ty` we
-            // could get `Option<NonStructEq>`, even though `Option` is annotated with derive.
-            && let Some(non_sm_ty) = traits::search_for_structural_match_violation(span, tcx, ty)
-        {
-            self.saw_const_match_lint.set(true);
-            tcx.emit_node_span_lint(
-                lint::builtin::NONTRIVIAL_STRUCTURAL_MATCH,
-                id,
-                span,
-                NontrivialStructuralMatch { non_sm_ty },
-            );
-        }
-
         Ok(Box::new(Pat { span, ty, kind }))
     }
 }

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

@@ -542,7 +542,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
 
         match const_value {
             Ok(const_) => {
-                let pattern = self.const_to_pat(const_, id, span, Some(instance.def_id()));
+                let pattern = self.const_to_pat(const_, id, span);
 
                 if !is_associated_const {
                     return pattern;
@@ -612,7 +612,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         };
         if let Some(lit_input) = lit_input {
             match tcx.at(expr.span).lit_to_const(lit_input) {
-                Ok(c) => return self.const_to_pat(Const::Ty(c), id, span, None).kind,
+                Ok(c) => return self.const_to_pat(Const::Ty(c), id, span).kind,
                 // If an error occurred, ignore that it's a literal
                 // and leave reporting the error up to const eval of
                 // the unevaluated constant below.
@@ -635,17 +635,13 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         if let Ok(Some(valtree)) =
             self.tcx.const_eval_resolve_for_typeck(self.param_env, ct, Some(span))
         {
-            let subpattern = self.const_to_pat(
+            let subpattern =
-                Const::Ty(ty::Const::new_value(self.tcx, valtree, ty)),
+                self.const_to_pat(Const::Ty(ty::Const::new_value(self.tcx, valtree, ty)), id, span);
-                id,
-                span,
-                None,
-            );
             PatKind::InlineConstant { subpattern, def: def_id }
         } else {
             // If that fails, convert it to an opaque constant pattern.
             match tcx.const_eval_resolve(self.param_env, uneval, Some(span)) {
-                Ok(val) => self.const_to_pat(mir::Const::Val(val, ty), id, span, None).kind,
+                Ok(val) => self.const_to_pat(mir::Const::Val(val, ty), id, span).kind,
                 Err(ErrorHandled::TooGeneric(_)) => {
                     // If we land here it means the const can't be evaluated because it's `TooGeneric`.
                     let e = self.tcx.dcx().emit_err(ConstPatternDependsOnGenericParameter { span });
@@ -681,9 +677,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         let lit_input =
             LitToConstInput { lit: &lit.node, ty: self.typeck_results.expr_ty(expr), neg };
         match self.tcx.at(expr.span).lit_to_const(lit_input) {
-            Ok(constant) => {
+            Ok(constant) => self.const_to_pat(Const::Ty(constant), expr.hir_id, lit.span).kind,
-                self.const_to_pat(Const::Ty(constant), expr.hir_id, lit.span, None).kind
-            }
             Err(LitToConstError::Reported(e)) => PatKind::Error(e),
             Err(LitToConstError::TypeError) => bug!("lower_lit: had type error"),
         }

tests/ui/consts/const_in_pattern/accept_corner_cases.rs

@@ -2,9 +2,8 @@
 
 // This test is checking our logic for structural match checking by enumerating
 // the different kinds of const expressions. This test is collecting cases where
-// we have accepted the const expression as a pattern in the past but we want
+// we have accepted the const expression as a pattern in the past and wish to
-// to begin warning the user that a future version of Rust may start rejecting
+// continue doing so.
-// such const expressions.
 
 // The specific corner cases we are exploring here are instances where the
 // const-evaluator computes a value that *does* meet the conditions for
@@ -24,18 +23,12 @@ impl Eq for NoDerive { }
 fn main() {
     const INDEX: Option<NoDerive> = [None, Some(NoDerive(10))][0];
     match None { Some(_) => panic!("whoops"), INDEX => dbg!(INDEX), };
-    //~^ WARN must be annotated with `#[derive(PartialEq)]`
-    //~| WARN this was previously accepted
 
     const fn build() -> Option<NoDerive> { None }
     const CALL: Option<NoDerive> = build();
     match None { Some(_) => panic!("whoops"), CALL => dbg!(CALL), };
-    //~^ WARN must be annotated with `#[derive(PartialEq)]`
-    //~| WARN this was previously accepted
 
     impl NoDerive { const fn none() -> Option<NoDerive> { None } }
     const METHOD_CALL: Option<NoDerive> = NoDerive::none();
     match None { Some(_) => panic!("whoops"), METHOD_CALL => dbg!(METHOD_CALL), };
-    //~^ WARN must be annotated with `#[derive(PartialEq)]`
-    //~| WARN this was previously accepted
 }

tests/ui/consts/const_in_pattern/custom-eq-branch-pass.rs

@@ -12,6 +12,7 @@ impl PartialEq for CustomEq {
 }
 
 #[derive(PartialEq, Eq)]
+#[allow(unused)]
 enum Foo {
     Bar,
     Baz,
@@ -21,7 +22,7 @@ enum Foo {
 const BAR_BAZ: Foo = if 42 == 42 {
     Foo::Bar
 } else {
-    Foo::Baz
+    Foo::Qux(CustomEq) // dead arm
 };
 
 fn main() {

tests/ui/consts/const_in_pattern/custom-eq-branch-warn.rs

@@ -1,38 +0,0 @@
-// check-pass
-
-struct CustomEq;
-
-impl Eq for CustomEq {}
-impl PartialEq for CustomEq {
-    fn eq(&self, _: &Self) -> bool {
-        false
-    }
-}
-
-#[derive(PartialEq, Eq)]
-enum Foo {
-    Bar,
-    Baz,
-    Qux(CustomEq),
-}
-
-// We know that `BAR_BAZ` will always be `Foo::Bar` and thus eligible for structural matching, but
-// dataflow will be more conservative.
-const BAR_BAZ: Foo = if 42 == 42 {
-    Foo::Bar
-} else {
-    Foo::Qux(CustomEq)
-};
-
-fn main() {
-    match Foo::Qux(CustomEq) {
-        BAR_BAZ => panic!(),
-        //~^ WARN must be annotated with `#[derive(PartialEq)]`
-        //~| NOTE the traits must be derived
-        //~| NOTE StructuralPartialEq.html for details
-        //~| WARN this was previously accepted
-        //~| NOTE see issue #73448
-        //~| NOTE `#[warn(nontrivial_structural_match)]` on by default
-        _ => {}
-    }
-}

tests/ui/consts/const_in_pattern/custom-eq-branch-warn.stderr

@@ -1,14 +0,0 @@
-warning: to use a constant of type `CustomEq` in a pattern, the constant's initializer must be trivial or `CustomEq` must be annotated with `#[derive(PartialEq)]`
-  --> $DIR/custom-eq-branch-warn.rs:29:9
-   |
-LL |         BAR_BAZ => panic!(),
-   |         ^^^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #73448 <https://github.com/rust-lang/rust/issues/73448>
-   = note: the traits must be derived, manual `impl`s are not sufficient
-   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
-   = note: `#[warn(nontrivial_structural_match)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/consts/const_in_pattern/issue-73431.stderr

@@ -1 +0,0 @@
-WARN rustc_mir_build::thir::pattern::const_to_pat MIR const-checker found novel structural match violation. See #73448.

tests/ui/consts/const_in_pattern/warn_corner_cases.stderr

@@ -1,36 +0,0 @@
-warning: to use a constant of type `NoDerive` in a pattern, the constant's initializer must be trivial or `NoDerive` must be annotated with `#[derive(PartialEq)]`
-  --> $DIR/warn_corner_cases.rs:26:47
-   |
-LL |     match None { Some(_) => panic!("whoops"), INDEX => dbg!(INDEX), };
-   |                                               ^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #73448 <https://github.com/rust-lang/rust/issues/73448>
-   = note: the traits must be derived, manual `impl`s are not sufficient
-   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
-   = note: `#[warn(nontrivial_structural_match)]` on by default
-
-warning: to use a constant of type `NoDerive` in a pattern, the constant's initializer must be trivial or `NoDerive` must be annotated with `#[derive(PartialEq)]`
-  --> $DIR/warn_corner_cases.rs:32:47
-   |
-LL |     match None { Some(_) => panic!("whoops"), CALL => dbg!(CALL), };
-   |                                               ^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #73448 <https://github.com/rust-lang/rust/issues/73448>
-   = note: the traits must be derived, manual `impl`s are not sufficient
-   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
-
-warning: to use a constant of type `NoDerive` in a pattern, the constant's initializer must be trivial or `NoDerive` must be annotated with `#[derive(PartialEq)]`
-  --> $DIR/warn_corner_cases.rs:38:47
-   |
-LL |     match None { Some(_) => panic!("whoops"), METHOD_CALL => dbg!(METHOD_CALL), };
-   |                                               ^^^^^^^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #73448 <https://github.com/rust-lang/rust/issues/73448>
-   = note: the traits must be derived, manual `impl`s are not sufficient
-   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
-
-warning: 3 warnings emitted
-

tests/ui/rfcs/rfc-1445-restrict-constants-in-patterns/issue-62307-match-ref-ref-forbidden-without-eq.rs

@@ -10,7 +10,7 @@
 
 // Issue 62307 pointed out a case where the structural-match checking
 // was too shallow.
-#![warn(indirect_structural_match, nontrivial_structural_match)]
+#![warn(indirect_structural_match)]
 // run-pass
 
 #[derive(Debug)]

tests/ui/rfcs/rfc-1445-restrict-constants-in-patterns/issue-62307-match-ref-ref-forbidden-without-eq.stderr

@@ -11,7 +11,7 @@ LL |         RR_B1 => { println!("CLAIM RR0: {:?} matches {:?}", RR_B1, RR_B0);
 note: the lint level is defined here
   --> $DIR/issue-62307-match-ref-ref-forbidden-without-eq.rs:13:9
    |
-LL | #![warn(indirect_structural_match, nontrivial_structural_match)]
+LL | #![warn(indirect_structural_match)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: to use a constant of type `B` in a pattern, `B` must be annotated with `#[derive(PartialEq)]`