From 010f3944e0f0baac8d738da49772fd06acd3701b Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Sat, 17 Feb 2024 01:23:40 +1100
Subject: [PATCH 1/2] Convert `delayed_bug`s to `bug`s.

I have a suspicion that quite a few delayed bug paths are impossible to
reach, so I did an experiment.

I converted every `delayed_bug` to a `bug`, ran the full test suite,
then converted back every `bug` that was hit. A surprising number were
never hit.

The next commit will convert some more back, based on human judgment.
---
 compiler/rustc_ast_lowering/src/lib.rs        |  4 +--
 .../src/diagnostics/region_name.rs            |  2 +-
 .../src/type_check/free_region_relations.rs   |  3 +-
 .../src/type_check/input_output.rs            |  3 +-
 compiler/rustc_borrowck/src/type_check/mod.rs | 12 ++++----
 .../src/const_eval/machine.rs                 |  8 ++---
 .../src/transform/check_consts/check.rs       |  4 +--
 .../src/transform/validate.rs                 |  2 +-
 .../rustc_hir_analysis/src/astconv/mod.rs     |  3 +-
 .../rustc_hir_analysis/src/check/check.rs     |  7 ++---
 .../src/check/compare_impl_item.rs            | 14 ++++-----
 .../src/check/compare_impl_item/refine.rs     |  9 ++----
 .../rustc_hir_analysis/src/check/dropck.rs    |  3 +-
 .../rustc_hir_analysis/src/check/wfcheck.rs   |  6 ++--
 .../src/collect/generics_of.rs                |  2 +-
 .../src/collect/resolve_bound_vars.rs         |  9 +++---
 compiler/rustc_hir_typeck/src/cast.rs         |  5 +---
 compiler/rustc_hir_typeck/src/expr.rs         | 15 +++-------
 compiler/rustc_hir_typeck/src/intrinsicck.rs  |  3 +-
 .../src/mem_categorization.rs                 |  6 ++--
 compiler/rustc_hir_typeck/src/method/probe.rs |  3 +-
 .../rustc_hir_typeck/src/method/suggest.rs    |  2 +-
 compiler/rustc_hir_typeck/src/pat.rs          |  5 +---
 .../src/infer/outlives/obligations.rs         |  2 +-
 .../rustc_infer/src/infer/outlives/verify.rs  |  6 +---
 compiler/rustc_infer/src/infer/relate/nll.rs  |  8 ++---
 .../rustc_middle/src/ty/typeck_results.rs     |  3 +-
 compiler/rustc_middle/src/ty/util.rs          |  4 +--
 compiler/rustc_middle/src/util/bug.rs         |  2 +-
 .../src/build/expr/as_constant.rs             | 15 ++++------
 compiler/rustc_mir_build/src/thir/constant.rs | 29 +++++++------------
 .../rustc_mir_build/src/thir/pattern/mod.rs   |  2 +-
 compiler/rustc_mir_transform/src/coroutine.rs |  6 +---
 .../src/elaborate_drops.rs                    |  2 +-
 compiler/rustc_resolve/src/late.rs            |  4 +--
 .../src/traits/const_evaluatable.rs           |  6 ++--
 .../error_reporting/type_err_ctxt_ext.rs      |  2 +-
 .../rustc_trait_selection/src/traits/mod.rs   |  2 +-
 .../src/traits/outlives_bounds.rs             |  2 +-
 .../src/traits/project.rs                     |  5 ++--
 .../src/traits/query/type_op/custom.rs        |  2 +-
 .../src/traits/query/type_op/mod.rs           |  7 ++---
 compiler/rustc_ty_utils/src/layout.rs         |  3 +-
 compiler/rustc_ty_utils/src/opaque_types.rs   |  2 +-
 44 files changed, 87 insertions(+), 157 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index a5be91bb87209..ef843da7307d3 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1636,9 +1636,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     if let Some(old_def_id) = self.orig_opt_local_def_id(param) {
                         old_def_id
                     } else {
-                        self.dcx()
-                            .span_delayed_bug(lifetime.ident.span, "no def-id for fresh lifetime");
-                        continue;
+                        self.dcx().span_bug(lifetime.ident.span, "no def-id for fresh lifetime");
                     }
                 }
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index 5b235066ea6cb..fea8c5a6de665 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -628,7 +628,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                 ) => {
                     // HIR lowering sometimes doesn't catch this in erroneous
                     // programs, so we need to use span_delayed_bug here. See #82126.
-                    self.dcx().span_delayed_bug(
+                    self.dcx().span_bug(
                         hir_arg.span(),
                         format!("unmatched arg and hir arg: found {kind:?} vs {hir_arg:?}"),
                     );
diff --git a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
index 356f0024c071e..0fc0417570594 100644
--- a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
+++ b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
@@ -316,8 +316,7 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
                     .and(type_op::normalize::Normalize::new(ty))
                     .fully_perform(self.infcx, span)
                 else {
-                    tcx.dcx().span_delayed_bug(span, format!("failed to normalize {ty:?}"));
-                    continue;
+                    tcx.dcx().span_bug(span, format!("failed to normalize {ty:?}"));
                 };
                 constraints.extend(c);
 
diff --git a/compiler/rustc_borrowck/src/type_check/input_output.rs b/compiler/rustc_borrowck/src/type_check/input_output.rs
index af5b635ae6688..8af78b08f69c1 100644
--- a/compiler/rustc_borrowck/src/type_check/input_output.rs
+++ b/compiler/rustc_borrowck/src/type_check/input_output.rs
@@ -154,8 +154,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             if argument_index + 1 >= body.local_decls.len() {
                 self.tcx()
                     .dcx()
-                    .span_delayed_bug(body.span, "found more normalized_input_ty than local_decls");
-                break;
+                    .span_bug(body.span, "found more normalized_input_ty than local_decls");
             }
 
             // In MIR, argument N is stored in local N+1.
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index f96c2cbd8c05b..81193902f9b32 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -220,14 +220,13 @@ pub(crate) fn type_check<'mir, 'tcx>(
                     "opaque_type_map",
                 ),
             );
-            let mut hidden_type = infcx.resolve_vars_if_possible(decl.hidden_type);
+            let hidden_type = infcx.resolve_vars_if_possible(decl.hidden_type);
             trace!("finalized opaque type {:?} to {:#?}", opaque_type_key, hidden_type.ty.kind());
             if hidden_type.has_non_region_infer() {
-                let reported = infcx.dcx().span_delayed_bug(
+                infcx.dcx().span_bug(
                     decl.hidden_type.span,
                     format!("could not resolve {:#?}", hidden_type.ty.kind()),
                 );
-                hidden_type.ty = Ty::new_error(infcx.tcx, reported);
             }
 
             (opaque_type_key, hidden_type)
@@ -1089,10 +1088,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         );
 
         if result.is_err() {
-            self.infcx.dcx().span_delayed_bug(
-                self.body.span,
-                "failed re-defining predefined opaques in mir typeck",
-            );
+            self.infcx
+                .dcx()
+                .span_bug(self.body.span, "failed re-defining predefined opaques in mir typeck");
         }
     }
 
diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs
index 2c60ede79758c..77744945b12fe 100644
--- a/compiler/rustc_const_eval/src/const_eval/machine.rs
+++ b/compiler/rustc_const_eval/src/const_eval/machine.rs
@@ -393,11 +393,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                 if ecx.tcx.is_ctfe_mir_available(def) {
                     Ok(ecx.tcx.mir_for_ctfe(def))
                 } else if ecx.tcx.def_kind(def) == DefKind::AssocConst {
-                    let guar = ecx
-                        .tcx
-                        .dcx()
-                        .delayed_bug("This is likely a const item that is missing from its impl");
-                    throw_inval!(AlreadyReported(guar.into()));
+                    ecx.tcx.dcx().bug("This is likely a const item that is missing from its impl");
                 } else {
                     // `find_mir_or_eval_fn` checks that this is a const fn before even calling us,
                     // so this should be unreachable.
@@ -626,7 +622,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                 );
                 // If this was a hard error, don't bother continuing evaluation.
                 if is_error {
-                    let guard = ecx
+                    let guard: rustc_errors::ErrorGuaranteed = ecx
                         .tcx
                         .dcx()
                         .span_delayed_bug(span, "The deny lint should have already errored");
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/check.rs b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
index 26ef083219f97..effaedd0820c3 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
@@ -329,9 +329,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
 
     fn check_static(&mut self, def_id: DefId, span: Span) {
         if self.tcx.is_thread_local_static(def_id) {
-            self.tcx
-                .dcx()
-                .span_delayed_bug(span, "tls access is checked in `Rvalue::ThreadLocalRef`");
+            self.tcx.dcx().span_bug(span, "tls access is checked in `Rvalue::ThreadLocalRef`");
         }
         self.check_op_spanned(ops::StaticAccess, span)
     }
diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs
index 1ff72516324c3..cc49e8ea247f7 100644
--- a/compiler/rustc_const_eval/src/transform/validate.rs
+++ b/compiler/rustc_const_eval/src/transform/validate.rs
@@ -517,7 +517,7 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
 
     fn visit_source_scope(&mut self, scope: SourceScope) {
         if self.body.source_scopes.get(scope).is_none() {
-            self.tcx.dcx().span_delayed_bug(
+            self.tcx.dcx().span_bug(
                 self.body.span,
                 format!(
                     "broken MIR in {:?} ({}):\ninvalid source scope {:?}",
diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs
index 502e83db65473..385b1f2a3e377 100644
--- a/compiler/rustc_hir_analysis/src/astconv/mod.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs
@@ -1237,8 +1237,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 // trait reference.
                 let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) else {
                     // A cycle error occurred, most likely.
-                    let guar = tcx.dcx().span_delayed_bug(span, "expected cycle error");
-                    return Err(guar);
+                    tcx.dcx().span_bug(span, "expected cycle error");
                 };
 
                 self.one_bound_for_assoc_item(
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index b3700013f9c2d..b945eed54d048 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -257,8 +257,7 @@ fn check_static_inhabited(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 fn check_opaque(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     let item = tcx.hir().expect_item(def_id);
     let hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) = item.kind else {
-        tcx.dcx().span_delayed_bug(item.span, "expected opaque item");
-        return;
+        tcx.dcx().span_bug(item.span, "expected opaque item");
     };
 
     // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
@@ -382,10 +381,10 @@ fn check_opaque_meets_bounds<'tcx>(
         Ok(()) => {}
         Err(ty_err) => {
             let ty_err = ty_err.to_string(tcx);
-            return Err(tcx.dcx().span_delayed_bug(
+            tcx.dcx().span_bug(
                 span,
                 format!("could not unify `{hidden_ty}` with revealed type:\n{ty_err}"),
-            ));
+            );
         }
     }
 
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 1dd27f0cc5314..42a64d8670de7 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -734,11 +734,8 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
                 remapped_types.insert(def_id, ty::EarlyBinder::bind(ty));
             }
             Err(err) => {
-                let reported = tcx.dcx().span_delayed_bug(
-                    return_span,
-                    format!("could not fully resolve: {ty} => {err:?}"),
-                );
-                remapped_types.insert(def_id, ty::EarlyBinder::bind(Ty::new_error(tcx, reported)));
+                tcx.dcx()
+                    .span_bug(return_span, format!("could not fully resolve: {ty} => {err:?}"));
             }
         }
     }
@@ -917,7 +914,7 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
                         .with_note(format!("hidden type inferred to be `{}`", self.ty))
                         .emit()
                 }
-                _ => self.tcx.dcx().delayed_bug("should've been able to remap region"),
+                _ => self.tcx.dcx().bug("should've been able to remap region"),
             };
             return Err(guar);
         };
@@ -1276,9 +1273,8 @@ fn compare_number_of_generics<'tcx>(
     // inheriting the generics from will also have mismatched arguments, and
     // we'll report an error for that instead. Delay a bug for safety, though.
     if trait_.is_impl_trait_in_trait() {
-        return Err(tcx.dcx().delayed_bug(
-            "errors comparing numbers of generics of trait/impl functions were not emitted",
-        ));
+        tcx.dcx()
+            .bug("errors comparing numbers of generics of trait/impl functions were not emitted");
     }
 
     let matchings = [
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
index 3d3b21eabb383..da40d6a860e6b 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
@@ -154,8 +154,7 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
         trait_m_sig.inputs_and_output,
     ));
     if !ocx.select_all_or_error().is_empty() {
-        tcx.dcx().delayed_bug("encountered errors when checking RPITIT refinement (selection)");
-        return;
+        tcx.dcx().bug("encountered errors when checking RPITIT refinement (selection)");
     }
     let outlives_env = OutlivesEnvironment::with_bounds(
         param_env,
@@ -163,13 +162,11 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
     );
     let errors = infcx.resolve_regions(&outlives_env);
     if !errors.is_empty() {
-        tcx.dcx().delayed_bug("encountered errors when checking RPITIT refinement (regions)");
-        return;
+        tcx.dcx().bug("encountered errors when checking RPITIT refinement (regions)");
     }
     // Resolve any lifetime variables that may have been introduced during normalization.
     let Ok((trait_bounds, impl_bounds)) = infcx.fully_resolve((trait_bounds, impl_bounds)) else {
-        tcx.dcx().delayed_bug("encountered errors when checking RPITIT refinement (resolution)");
-        return;
+        tcx.dcx().bug("encountered errors when checking RPITIT refinement (resolution)");
     };
 
     // For quicker lookup, use an `IndexSet` (we don't use one earlier because
diff --git a/compiler/rustc_hir_analysis/src/check/dropck.rs b/compiler/rustc_hir_analysis/src/check/dropck.rs
index 82a6b6b6f2cb5..9b46b415491ff 100644
--- a/compiler/rustc_hir_analysis/src/check/dropck.rs
+++ b/compiler/rustc_hir_analysis/src/check/dropck.rs
@@ -67,11 +67,10 @@ pub fn check_drop_impl(tcx: TyCtxt<'_>, drop_impl_did: DefId) -> Result<(), Erro
             // already checked by coherence, but compilation may
             // not have been terminated.
             let span = tcx.def_span(drop_impl_did);
-            let reported = tcx.dcx().span_delayed_bug(
+            tcx.dcx().span_bug(
                 span,
                 format!("should have been rejected by coherence check: {dtor_self_type}"),
             );
-            Err(reported)
         }
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index e7506cee60e7c..81d8a51485f12 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -1088,10 +1088,8 @@ fn check_type_defn<'tcx>(
                     let ty = tcx.type_of(variant.tail().did).instantiate_identity();
                     let ty = tcx.erase_regions(ty);
                     if ty.has_infer() {
-                        tcx.dcx()
-                            .span_delayed_bug(item.span, format!("inference variables in {ty:?}"));
-                        // Just treat unresolved type expression as if it needs drop.
-                        true
+                        // Unresolved type expression.
+                        tcx.dcx().span_bug(item.span, format!("inference variables in {ty:?}"));
                     } else {
                         ty.needs_drop(tcx, tcx.param_env(item.owner_id))
                     }
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index 9cc6c16c12639..410a069f9568f 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -315,7 +315,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
 
             if is_host_effect {
                 if let Some(idx) = host_effect_index {
-                    tcx.dcx().span_delayed_bug(
+                    tcx.dcx().span_bug(
                         param.span,
                         format!("parent also has host effect param? index: {idx}, def: {def_id:?}"),
                     );
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 325a0ee9a18fd..efde4e11c79dd 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -1331,7 +1331,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             }
         }
 
-        self.tcx.dcx().span_delayed_bug(
+        self.tcx.dcx().span_bug(
             lifetime_ref.ident.span,
             format!("Could not resolve {:?} in scope {:#?}", lifetime_ref, self.scope,),
         );
@@ -1465,10 +1465,9 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             }
         }
 
-        self.tcx.dcx().span_delayed_bug(
-            self.tcx.hir().span(hir_id),
-            format!("could not resolve {param_def_id:?}"),
-        );
+        self.tcx
+            .dcx()
+            .span_bug(self.tcx.hir().span(hir_id), format!("could not resolve {param_def_id:?}"));
     }
 
     #[instrument(level = "debug", skip(self))]
diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs
index 48fc2900b0d5e..b662d23c27150 100644
--- a/compiler/rustc_hir_typeck/src/cast.rs
+++ b/compiler/rustc_hir_typeck/src/cast.rs
@@ -139,10 +139,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             | ty::Never
             | ty::Dynamic(_, _, ty::DynStar)
             | ty::Error(_) => {
-                let guar = self
-                    .dcx()
-                    .span_delayed_bug(span, format!("`{t:?}` should be sized but is not?"));
-                return Err(guar);
+                self.dcx().span_bug(span, format!("`{t:?}` should be sized but is not?"));
             }
         })
     }
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 0f6544c3e1f9c..0a636fa9eacd0 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -76,16 +76,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // While we don't allow *arbitrary* coercions here, we *do* allow
         // coercions from ! to `expected`.
         if ty.is_never() {
-            if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
-                let reported = self.dcx().span_delayed_bug(
-                    expr.span,
-                    "expression with never type wound up being adjusted",
-                );
-                return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
-                    target.to_owned()
-                } else {
-                    Ty::new_error(self.tcx(), reported)
-                };
+            if let Some(_) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
+                self.dcx()
+                    .span_bug(expr.span, "expression with never type wound up being adjusted");
             }
 
             let adj_ty = self.next_ty_var(TypeVariableOrigin {
@@ -1325,7 +1318,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // permit break with a value [1].
         if ctxt.coerce.is_none() && !ctxt.may_break {
             // [1]
-            self.dcx().span_delayed_bug(body.span, "no coercion, but loop may not break");
+            self.dcx().span_bug(body.span, "no coercion, but loop may not break");
         }
         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| Ty::new_unit(self.tcx))
     }
diff --git a/compiler/rustc_hir_typeck/src/intrinsicck.rs b/compiler/rustc_hir_typeck/src/intrinsicck.rs
index 2dee5093e876d..fd62afbae96aa 100644
--- a/compiler/rustc_hir_typeck/src/intrinsicck.rs
+++ b/compiler/rustc_hir_typeck/src/intrinsicck.rs
@@ -48,8 +48,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let to = normalize(to);
         trace!(?from, ?to);
         if from.has_non_region_infer() || to.has_non_region_infer() {
-            tcx.dcx().span_delayed_bug(span, "argument to transmute has inference variables");
-            return;
+            tcx.dcx().span_bug(span, "argument to transmute has inference variables");
         }
         // Transmutes that are only changing lifetimes are always ok.
         if from == to {
diff --git a/compiler/rustc_hir_typeck/src/mem_categorization.rs b/compiler/rustc_hir_typeck/src/mem_categorization.rs
index fefaf9967253b..c300ec7444b2e 100644
--- a/compiler/rustc_hir_typeck/src/mem_categorization.rs
+++ b/compiler/rustc_hir_typeck/src/mem_categorization.rs
@@ -570,8 +570,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
             _ => {
                 self.tcx()
                     .dcx()
-                    .span_delayed_bug(span, "struct or tuple struct pattern not applied to an ADT");
-                Err(())
+                    .span_bug(span, "struct or tuple struct pattern not applied to an ADT");
             }
         }
     }
@@ -583,8 +582,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
         match ty.kind() {
             ty::Tuple(args) => Ok(args.len()),
             _ => {
-                self.tcx().dcx().span_delayed_bug(span, "tuple pattern not applied to a tuple");
-                Err(())
+                self.tcx().dcx().span_bug(span, "tuple pattern not applied to a tuple");
             }
         }
     }
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index d7edc70bce82e..a58e194e20aed 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -804,11 +804,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         let trait_ref = principal.with_self_ty(self.tcx, self_ty);
         self.elaborate_bounds(iter::once(trait_ref), |this, new_trait_ref, item| {
             if new_trait_ref.has_non_region_bound_vars() {
-                this.dcx().span_delayed_bug(
+                this.dcx().span_bug(
                     this.span,
                     "tried to select method from HRTB with non-lifetime bound vars",
                 );
-                return;
             }
 
             let new_trait_ref = this.instantiate_bound_regions_with_erased(new_trait_ref);
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 005d217fdc44f..13f33abaa6451 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -924,7 +924,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         span: item_span,
                         ..
                     })) => {
-                        tcx.dcx().span_delayed_bug(
+                        tcx.dcx().span_bug(
                             *item_span,
                             "auto trait is invoked with no method error, but no error reported?",
                         );
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index 73689b45b95ba..b15c9ef901877 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -1085,10 +1085,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let variant = match res {
             Res::Err => {
-                let e = tcx.dcx().span_delayed_bug(pat.span, "`Res::Err` but no error emitted");
-                self.set_tainted_by_errors(e);
-                on_error(e);
-                return Ty::new_error(tcx, e);
+                tcx.dcx().span_bug(pat.span, "`Res::Err` but no error emitted");
             }
             Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) => {
                 let e = report_unexpected_res(res);
diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs
index c0a99e5cc4177..643fe83e89881 100644
--- a/compiler/rustc_infer/src/infer/outlives/obligations.rs
+++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs
@@ -303,7 +303,7 @@ where
                     // Ignore this, we presume it will yield an error later,
                     // since if a type variable is not resolved by this point
                     // it never will be.
-                    self.tcx.dcx().span_delayed_bug(
+                    self.tcx.dcx().span_bug(
                         origin.span(),
                         format!("unresolved inference variable in outlives: {v:?}"),
                     );
diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs
index 3ef37bf3466f1..515f44c914d07 100644
--- a/compiler/rustc_infer/src/infer/outlives/verify.rs
+++ b/compiler/rustc_infer/src/infer/outlives/verify.rs
@@ -175,11 +175,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
                 // Ignore this, we presume it will yield an error later, since
                 // if a type variable is not resolved by this point it never
                 // will be.
-                self.tcx
-                    .dcx()
-                    .delayed_bug(format!("unresolved inference variable in outlives: {v:?}"));
-                // Add a bound that never holds.
-                VerifyBound::AnyBound(vec![])
+                self.tcx.dcx().bug(format!("unresolved inference variable in outlives: {v:?}"));
             }
         }
     }
diff --git a/compiler/rustc_infer/src/infer/relate/nll.rs b/compiler/rustc_infer/src/infer/relate/nll.rs
index 4ba4bd38e9fe4..4cc6457df7a30 100644
--- a/compiler/rustc_infer/src/infer/relate/nll.rs
+++ b/compiler/rustc_infer/src/infer/relate/nll.rs
@@ -420,11 +420,9 @@ where
         match b.kind() {
             ty::ConstKind::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => {
                 // Forbid inference variables in the RHS.
-                self.infcx.dcx().span_delayed_bug(
-                    self.delegate.span(),
-                    format!("unexpected inference var {b:?}",),
-                );
-                Ok(a)
+                self.infcx
+                    .dcx()
+                    .span_bug(self.delegate.span(), format!("unexpected inference var {b:?}",));
             }
             // FIXME(invariance): see the related FIXME above.
             _ => self.infcx.super_combine_consts(self, a, b),
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index a03ee78a29a58..4287b382604ee 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -410,8 +410,7 @@ impl<'tcx> TypeckResults<'tcx> {
 
     pub fn extract_binding_mode(&self, s: &Session, id: HirId, sp: Span) -> Option<BindingMode> {
         self.pat_binding_modes().get(id).copied().or_else(|| {
-            s.dcx().span_delayed_bug(sp, "missing binding mode");
-            None
+            s.dcx().span_bug(sp, "missing binding mode");
         })
     }
 
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 3f539945841b6..95d55a7081db5 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -356,9 +356,7 @@ impl<'tcx> TyCtxt<'tcx> {
             }
 
             let Some(item_id) = self.associated_item_def_ids(impl_did).first() else {
-                self.dcx()
-                    .span_delayed_bug(self.def_span(impl_did), "Drop impl without drop function");
-                return;
+                self.dcx().span_bug(self.def_span(impl_did), "Drop impl without drop function");
             };
 
             if let Some((old_item_id, _)) = dtor_candidate {
diff --git a/compiler/rustc_middle/src/util/bug.rs b/compiler/rustc_middle/src/util/bug.rs
index a67ec99158210..dae6c0b9d68b8 100644
--- a/compiler/rustc_middle/src/util/bug.rs
+++ b/compiler/rustc_middle/src/util/bug.rs
@@ -42,7 +42,7 @@ fn opt_span_bug_fmt<S: Into<MultiSpan>>(
 /// delayed bug, so what is the point of this? It exists to help us test the interaction of delayed
 /// bugs with the query system and incremental.
 pub fn trigger_delayed_bug(tcx: TyCtxt<'_>, key: rustc_hir::def_id::DefId) {
-    tcx.dcx().span_delayed_bug(
+    tcx.dcx().span_bug(
         tcx.def_span(key),
         "delayed bug triggered by #[rustc_error(delayed_bug_from_inside_query)]",
     );
diff --git a/compiler/rustc_mir_build/src/build/expr/as_constant.rs b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
index 7c3d2671d592c..d66540d8e79e4 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_constant.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
@@ -110,15 +110,12 @@ fn lit_to_mir_constant<'tcx>(
     let LitToConstInput { lit, ty, neg } = lit_input;
     let trunc = |n| {
         let param_ty = ty::ParamEnv::reveal_all().and(ty);
-        let width =
-            tcx.layout_of(param_ty)
-                .map_err(|_| {
-                    LitToConstError::Reported(tcx.dcx().delayed_bug(format!(
-                        "couldn't compute width of literal: {:?}",
-                        lit_input.lit
-                    )))
-                })?
-                .size;
+        let width = tcx
+            .layout_of(param_ty)
+            .map_err(|_| {
+                tcx.dcx().bug(format!("couldn't compute width of literal: {:?}", lit_input.lit))
+            })?
+            .size;
         trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
         let result = width.truncate(n);
         trace!("trunc result: {}", result);
diff --git a/compiler/rustc_mir_build/src/thir/constant.rs b/compiler/rustc_mir_build/src/thir/constant.rs
index d444de8b28eec..46580432f1328 100644
--- a/compiler/rustc_mir_build/src/thir/constant.rs
+++ b/compiler/rustc_mir_build/src/thir/constant.rs
@@ -12,15 +12,12 @@ pub(crate) fn lit_to_const<'tcx>(
 
     let trunc = |n| {
         let param_ty = ParamEnv::reveal_all().and(ty);
-        let width =
-            tcx.layout_of(param_ty)
-                .map_err(|_| {
-                    LitToConstError::Reported(tcx.dcx().delayed_bug(format!(
-                        "couldn't compute width of literal: {:?}",
-                        lit_input.lit
-                    )))
-                })?
-                .size;
+        let width = tcx
+            .layout_of(param_ty)
+            .map_err(|_| {
+                tcx.dcx().bug(format!("couldn't compute width of literal: {:?}", lit_input.lit))
+            })?
+            .size;
         trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
         let result = width.truncate(n);
         trace!("trunc result: {}", result);
@@ -59,15 +56,11 @@ pub(crate) fn lit_to_const<'tcx>(
         }
         (ast::LitKind::Bool(b), ty::Bool) => ty::ValTree::from_scalar_int((*b).into()),
         (ast::LitKind::Float(n, _), ty::Float(fty)) => {
-            let bits =
-                parse_float_into_scalar(*n, *fty, neg)
-                    .ok_or_else(|| {
-                        LitToConstError::Reported(tcx.dcx().delayed_bug(format!(
-                            "couldn't parse float literal: {:?}",
-                            lit_input.lit
-                        )))
-                    })?
-                    .assert_int();
+            let bits = parse_float_into_scalar(*n, *fty, neg)
+                .ok_or_else(|| {
+                    tcx.dcx().bug(format!("couldn't parse float literal: {:?}", lit_input.lit))
+                })?
+                .assert_int();
             ty::ValTree::from_scalar_int(bits)
         }
         (ast::LitKind::Char(c), ty::Char) => ty::ValTree::from_scalar_int((*c).into()),
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
index 1a5cf13e28978..0329e1d3096dc 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -175,7 +175,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
     ) -> Result<PatKind<'tcx>, ErrorGuaranteed> {
         if lo_expr.is_none() && hi_expr.is_none() {
             let msg = "found twice-open range pattern (`..`) outside of error recovery";
-            return Err(self.tcx.dcx().span_delayed_bug(span, msg));
+            self.tcx.dcx().span_bug(span, msg);
         }
 
         let (lo, lo_ascr, lo_inline) = self.lower_pattern_range_endpoint(lo_expr)?;
diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/compiler/rustc_mir_transform/src/coroutine.rs
index a0851aa557b86..54b13a40e92dd 100644
--- a/compiler/rustc_mir_transform/src/coroutine.rs
+++ b/compiler/rustc_mir_transform/src/coroutine.rs
@@ -1615,11 +1615,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
                 (args.discr_ty(tcx), coroutine_kind.movability() == hir::Movability::Movable)
             }
             _ => {
-                tcx.dcx().span_delayed_bug(
-                    body.span,
-                    format!("unexpected coroutine type {coroutine_ty}"),
-                );
-                return;
+                tcx.dcx().span_bug(body.span, format!("unexpected coroutine type {coroutine_ty}"));
             }
         };
 
diff --git a/compiler/rustc_mir_transform/src/elaborate_drops.rs b/compiler/rustc_mir_transform/src/elaborate_drops.rs
index 8575f552f0ae7..03d952abad118 100644
--- a/compiler/rustc_mir_transform/src/elaborate_drops.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_drops.rs
@@ -380,7 +380,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
                 LookupResult::Parent(None) => {}
                 LookupResult::Parent(Some(_)) => {
                     if !replace {
-                        self.tcx.dcx().span_delayed_bug(
+                        self.tcx.dcx().span_bug(
                             terminator.source_info.span,
                             format!("drop of untracked value {bb:?}"),
                         );
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 6aacb0e17d576..676bc9db4a924 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -3681,13 +3681,13 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                 None
             }
             Res::SelfCtor(_) => {
+                // njn: remove comment?
                 // We resolve `Self` in pattern position as an ident sometimes during recovery,
                 // so delay a bug instead of ICEing.
-                self.r.dcx().span_delayed_bug(
+                self.r.dcx().span_bug(
                     ident.span,
                     "unexpected `SelfCtor` in pattern, expected identifier"
                 );
-                None
             }
             _ => span_bug!(
                 ident.span,
diff --git a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
index 1edf6b11fc343..79f423756fd7a 100644
--- a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
+++ b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
@@ -62,14 +62,12 @@ pub fn is_const_evaluatable<'tcx>(
 
         match unexpanded_ct.kind() {
             ty::ConstKind::Expr(_) => {
+                // njn: ?
                 // FIXME(generic_const_exprs): we have a `ConstKind::Expr` which is fully concrete,
                 // but currently it is not possible to evaluate `ConstKind::Expr` so we are unable
                 // to tell if it is evaluatable or not. For now we just ICE until this is
                 // implemented.
-                Err(NotConstEvaluatable::Error(tcx.dcx().span_delayed_bug(
-                    span,
-                    "evaluating `ConstKind::Expr` is not currently supported",
-                )))
+                tcx.dcx().span_bug(span, "evaluating `ConstKind::Expr` is not currently supported");
             }
             ty::ConstKind::Unevaluated(uv) => {
                 let concrete = infcx.const_eval_resolve(param_env, uv, Some(span));
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index 4f674ac7583c9..aa8bd5fdc866b 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -3313,7 +3313,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         expected_trait_ref.self_ty().error_reported()?;
 
         let Some(found_trait_ty) = found_trait_ref.self_ty().no_bound_vars() else {
-            return Err(self.dcx().delayed_bug("bound vars outside binder"));
+            self.dcx().bug("bound vars outside binder");
         };
 
         let found_did = match *found_trait_ty.kind() {
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index 9eec60ea06c21..43f709352a293 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -172,7 +172,7 @@ fn do_normalize_predicates<'tcx>(
     // the normalized predicates.
     let errors = infcx.resolve_regions(&outlives_env);
     if !errors.is_empty() {
-        tcx.dcx().span_delayed_bug(
+        tcx.dcx().span_bug(
             span,
             format!("failed region resolution while normalizing {elaborated_env:?}: {errors:?}"),
         );
diff --git a/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
index 8b2e8b54aee64..c4110df45dbb4 100644
--- a/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
+++ b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
@@ -100,7 +100,7 @@ fn implied_outlives_bounds<'a, 'tcx>(
 
         let errors = ocx.select_all_or_error();
         if !errors.is_empty() {
-            infcx.dcx().span_delayed_bug(
+            infcx.dcx().span_bug(
                 span,
                 "implied_outlives_bounds failed to solve obligations from instantiation",
             );
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 9c532ea4d8d85..dc5b62fbd1c72 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -645,7 +645,7 @@ pub fn compute_inherent_assoc_ty_args<'a, 'b, 'tcx>(
     match selcx.infcx.at(&cause, param_env).eq(DefineOpaqueTypes::No, impl_ty, self_ty) {
         Ok(mut ok) => obligations.append(&mut ok.obligations),
         Err(_) => {
-            tcx.dcx().span_delayed_bug(
+            tcx.dcx().span_bug(
                 cause.span,
                 format!(
                     "{self_ty:?} was a subtype of {impl_ty:?} during selection but now it is not"
@@ -1190,11 +1190,10 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
             ImplSource::Builtin(BuiltinImplSource::TraitUpcasting { .. }, _)
             | ImplSource::Builtin(BuiltinImplSource::TupleUnsizing, _) => {
                 // These traits have no associated types.
-                selcx.tcx().dcx().span_delayed_bug(
+                selcx.tcx().dcx().span_bug(
                     obligation.cause.span,
                     format!("Cannot project an associated type from `{impl_source:?}`"),
                 );
-                return Err(());
             }
         };
 
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
index d533e69a4fa7f..a8d9b0f42d94e 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
@@ -82,7 +82,7 @@ where
     let value = infcx.commit_if_ok(|_| {
         let ocx = ObligationCtxt::new(infcx);
         let value = op(&ocx).map_err(|_| {
-            infcx.dcx().span_delayed_bug(span, format!("error performing operation: {name}"))
+            infcx.dcx().span_bug(span, format!("error performing operation: {name}"))
         })?;
         let errors = ocx.select_all_or_error();
         if errors.is_empty() {
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
index fb09f094d37ae..12ee778ee05c6 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
@@ -190,10 +190,9 @@ where
                 }
             }
             if !progress {
-                return Err(infcx.dcx().span_delayed_bug(
-                    span,
-                    format!("ambiguity processing {obligations:?} from {self:?}"),
-                ));
+                infcx
+                    .dcx()
+                    .span_bug(span, format!("ambiguity processing {obligations:?} from {self:?}"));
             }
         }
 
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index 96f8148bf7204..b00330d335e43 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -90,8 +90,7 @@ fn univariant_uninterned<'tcx>(
     let dl = cx.data_layout();
     let pack = repr.pack;
     if pack.is_some() && repr.align.is_some() {
-        cx.tcx.dcx().delayed_bug("struct cannot be packed and aligned");
-        return Err(cx.tcx.arena.alloc(LayoutError::Unknown(ty)));
+        cx.tcx.dcx().bug("struct cannot be packed and aligned");
     }
 
     cx.univariant(dl, fields, repr, kind).ok_or_else(|| error(cx, LayoutError::SizeOverflow(ty)))
diff --git a/compiler/rustc_ty_utils/src/opaque_types.rs b/compiler/rustc_ty_utils/src/opaque_types.rs
index 329cf32cad5ea..86c7551882aab 100644
--- a/compiler/rustc_ty_utils/src/opaque_types.rs
+++ b/compiler/rustc_ty_utils/src/opaque_types.rs
@@ -337,7 +337,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInAssocTypeCollector<'tcx> {
                                 .instantiate(self.0.tcx, impl_args)
                                 .visit_with(self);
                         } else {
-                            self.0.tcx.dcx().span_delayed_bug(
+                            self.0.tcx.dcx().span_bug(
                                 self.0.tcx.def_span(assoc.def_id),
                                 "item had incorrect args",
                             );

From 2903bbbc156fb9707b43038af6723844fd4ccf29 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Tue, 20 Feb 2024 09:36:28 +1100
Subject: [PATCH 2/2] Convert `bug`s back to `delayed_bug`s.

This commit undoes some of the previous commit's mechanical changes,
based on human judgment.
---
 .../rustc_borrowck/src/diagnostics/region_name.rs  |  4 ++--
 .../src/type_check/free_region_relations.rs        |  6 +++++-
 .../rustc_const_eval/src/const_eval/machine.rs     |  2 +-
 .../src/check/compare_impl_item.rs                 | 14 +++++++++++++-
 .../src/check/compare_impl_item/refine.rs          |  9 +++++++++
 compiler/rustc_hir_analysis/src/check/dropck.rs    |  3 ++-
 compiler/rustc_hir_analysis/src/check/wfcheck.rs   |  8 ++------
 compiler/rustc_hir_typeck/src/expr.rs              |  3 +--
 compiler/rustc_hir_typeck/src/intrinsicck.rs       |  3 +++
 compiler/rustc_hir_typeck/src/method/suggest.rs    |  2 +-
 .../rustc_infer/src/infer/outlives/obligations.rs  |  2 +-
 compiler/rustc_infer/src/infer/outlives/verify.rs  |  6 +++++-
 compiler/rustc_infer/src/infer/relate/nll.rs       |  2 +-
 compiler/rustc_middle/src/ty/util.rs               |  4 +++-
 compiler/rustc_middle/src/util/bug.rs              |  2 +-
 .../rustc_mir_build/src/build/expr/as_constant.rs  | 10 +++++-----
 compiler/rustc_mir_build/src/thir/constant.rs      | 10 +++++-----
 compiler/rustc_resolve/src/late.rs                 |  4 ++--
 .../src/traits/const_evaluatable.rs                |  9 ++++-----
 compiler/rustc_trait_selection/src/traits/mod.rs   |  2 ++
 .../rustc_trait_selection/src/traits/project.rs    |  7 +++----
 .../src/traits/query/type_op/custom.rs             |  2 +-
 tests/ui/drop/missing-drop-method.rs               |  4 ++++
 tests/ui/drop/missing-drop-method.stderr           | 11 +++++++++++
 24 files changed, 87 insertions(+), 42 deletions(-)
 create mode 100644 tests/ui/drop/missing-drop-method.rs
 create mode 100644 tests/ui/drop/missing-drop-method.stderr

diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index fea8c5a6de665..e228bef1139a6 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -626,8 +626,8 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                     | GenericArgKind::Const(_),
                     _,
                 ) => {
-                    // HIR lowering sometimes doesn't catch this in erroneous
-                    // programs, so we need to use span_delayed_bug here. See #82126.
+                    // This was previously a `span_delayed_bug` and could be
+                    // reached by the test for #82126, but no longer.
                     self.dcx().span_bug(
                         hir_arg.span(),
                         format!("unmatched arg and hir arg: found {kind:?} vs {hir_arg:?}"),
diff --git a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
index 0fc0417570594..897918fb0a45b 100644
--- a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
+++ b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
@@ -316,7 +316,11 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
                     .and(type_op::normalize::Normalize::new(ty))
                     .fully_perform(self.infcx, span)
                 else {
-                    tcx.dcx().span_bug(span, format!("failed to normalize {ty:?}"));
+                    // Note: this path is currently not reached in any test, so
+                    // any example that triggers this would be worth minimizing
+                    // and converting into a test.
+                    tcx.dcx().span_delayed_bug(span, format!("failed to normalize {ty:?}"));
+                    continue;
                 };
                 constraints.extend(c);
 
diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs
index 77744945b12fe..946ffc05cc14f 100644
--- a/compiler/rustc_const_eval/src/const_eval/machine.rs
+++ b/compiler/rustc_const_eval/src/const_eval/machine.rs
@@ -622,7 +622,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                 );
                 // If this was a hard error, don't bother continuing evaluation.
                 if is_error {
-                    let guard: rustc_errors::ErrorGuaranteed = ecx
+                    let guard = ecx
                         .tcx
                         .dcx()
                         .span_delayed_bug(span, "The deny lint should have already errored");
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 42a64d8670de7..435e251b130ea 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -734,6 +734,10 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
                 remapped_types.insert(def_id, ty::EarlyBinder::bind(ty));
             }
             Err(err) => {
+                // This code path is not reached in any tests, but may be
+                // reachable. If this is triggered, it should be converted to
+                // `span_delayed_bug` and the triggering case turned into a
+                // test.
                 tcx.dcx()
                     .span_bug(return_span, format!("could not fully resolve: {ty} => {err:?}"));
             }
@@ -914,7 +918,13 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
                         .with_note(format!("hidden type inferred to be `{}`", self.ty))
                         .emit()
                 }
-                _ => self.tcx.dcx().bug("should've been able to remap region"),
+                _ => {
+                    // This code path is not reached in any tests, but may be
+                    // reachable. If this is triggered, it should be converted
+                    // to `delayed_bug` and the triggering case turned into a
+                    // test.
+                    self.tcx.dcx().bug("should've been able to remap region");
+                }
             };
             return Err(guar);
         };
@@ -1273,6 +1283,8 @@ fn compare_number_of_generics<'tcx>(
     // inheriting the generics from will also have mismatched arguments, and
     // we'll report an error for that instead. Delay a bug for safety, though.
     if trait_.is_impl_trait_in_trait() {
+        // FIXME: no tests trigger this. If you find example code that does
+        // trigger this, please add it to the test suite.
         tcx.dcx()
             .bug("errors comparing numbers of generics of trait/impl functions were not emitted");
     }
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
index da40d6a860e6b..7bdbab4325cbf 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
@@ -154,6 +154,9 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
         trait_m_sig.inputs_and_output,
     ));
     if !ocx.select_all_or_error().is_empty() {
+        // This code path is not reached in any tests, but may be reachable. If
+        // this is triggered, it should be converted to `delayed_bug` and the
+        // triggering case turned into a test.
         tcx.dcx().bug("encountered errors when checking RPITIT refinement (selection)");
     }
     let outlives_env = OutlivesEnvironment::with_bounds(
@@ -162,10 +165,16 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
     );
     let errors = infcx.resolve_regions(&outlives_env);
     if !errors.is_empty() {
+        // This code path is not reached in any tests, but may be reachable. If
+        // this is triggered, it should be converted to `delayed_bug` and the
+        // triggering case turned into a test.
         tcx.dcx().bug("encountered errors when checking RPITIT refinement (regions)");
     }
     // Resolve any lifetime variables that may have been introduced during normalization.
     let Ok((trait_bounds, impl_bounds)) = infcx.fully_resolve((trait_bounds, impl_bounds)) else {
+        // This code path is not reached in any tests, but may be reachable. If
+        // this is triggered, it should be converted to `delayed_bug` and the
+        // triggering case turned into a test.
         tcx.dcx().bug("encountered errors when checking RPITIT refinement (resolution)");
     };
 
diff --git a/compiler/rustc_hir_analysis/src/check/dropck.rs b/compiler/rustc_hir_analysis/src/check/dropck.rs
index 9b46b415491ff..82a6b6b6f2cb5 100644
--- a/compiler/rustc_hir_analysis/src/check/dropck.rs
+++ b/compiler/rustc_hir_analysis/src/check/dropck.rs
@@ -67,10 +67,11 @@ pub fn check_drop_impl(tcx: TyCtxt<'_>, drop_impl_did: DefId) -> Result<(), Erro
             // already checked by coherence, but compilation may
             // not have been terminated.
             let span = tcx.def_span(drop_impl_did);
-            tcx.dcx().span_bug(
+            let reported = tcx.dcx().span_delayed_bug(
                 span,
                 format!("should have been rejected by coherence check: {dtor_self_type}"),
             );
+            Err(reported)
         }
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index 81d8a51485f12..f03d0f8a88529 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -1087,12 +1087,8 @@ fn check_type_defn<'tcx>(
                 packed && {
                     let ty = tcx.type_of(variant.tail().did).instantiate_identity();
                     let ty = tcx.erase_regions(ty);
-                    if ty.has_infer() {
-                        // Unresolved type expression.
-                        tcx.dcx().span_bug(item.span, format!("inference variables in {ty:?}"));
-                    } else {
-                        ty.needs_drop(tcx, tcx.param_env(item.owner_id))
-                    }
+                    assert!(!ty.has_infer());
+                    ty.needs_drop(tcx, tcx.param_env(item.owner_id))
                 }
             };
             // All fields (except for possibly the last) should be sized.
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 0a636fa9eacd0..89cc46dc5ab80 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -1315,9 +1315,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // the LUB of the breaks (possibly ! if none); else, it
         // is nil. This makes sense because infinite loops
         // (which would have type !) are only possible iff we
-        // permit break with a value [1].
+        // permit break with a value.
         if ctxt.coerce.is_none() && !ctxt.may_break {
-            // [1]
             self.dcx().span_bug(body.span, "no coercion, but loop may not break");
         }
         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| Ty::new_unit(self.tcx))
diff --git a/compiler/rustc_hir_typeck/src/intrinsicck.rs b/compiler/rustc_hir_typeck/src/intrinsicck.rs
index fd62afbae96aa..9e3867e630d48 100644
--- a/compiler/rustc_hir_typeck/src/intrinsicck.rs
+++ b/compiler/rustc_hir_typeck/src/intrinsicck.rs
@@ -48,6 +48,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let to = normalize(to);
         trace!(?from, ?to);
         if from.has_non_region_infer() || to.has_non_region_infer() {
+            // Note: this path is currently not reached in any test, so any
+            // example that triggers this would be worth minimizing and
+            // converting into a test.
             tcx.dcx().span_bug(span, "argument to transmute has inference variables");
         }
         // Transmutes that are only changing lifetimes are always ok.
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 13f33abaa6451..005d217fdc44f 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -924,7 +924,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         span: item_span,
                         ..
                     })) => {
-                        tcx.dcx().span_bug(
+                        tcx.dcx().span_delayed_bug(
                             *item_span,
                             "auto trait is invoked with no method error, but no error reported?",
                         );
diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs
index 643fe83e89881..c0a99e5cc4177 100644
--- a/compiler/rustc_infer/src/infer/outlives/obligations.rs
+++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs
@@ -303,7 +303,7 @@ where
                     // Ignore this, we presume it will yield an error later,
                     // since if a type variable is not resolved by this point
                     // it never will be.
-                    self.tcx.dcx().span_bug(
+                    self.tcx.dcx().span_delayed_bug(
                         origin.span(),
                         format!("unresolved inference variable in outlives: {v:?}"),
                     );
diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs
index 515f44c914d07..3ef37bf3466f1 100644
--- a/compiler/rustc_infer/src/infer/outlives/verify.rs
+++ b/compiler/rustc_infer/src/infer/outlives/verify.rs
@@ -175,7 +175,11 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
                 // Ignore this, we presume it will yield an error later, since
                 // if a type variable is not resolved by this point it never
                 // will be.
-                self.tcx.dcx().bug(format!("unresolved inference variable in outlives: {v:?}"));
+                self.tcx
+                    .dcx()
+                    .delayed_bug(format!("unresolved inference variable in outlives: {v:?}"));
+                // Add a bound that never holds.
+                VerifyBound::AnyBound(vec![])
             }
         }
     }
diff --git a/compiler/rustc_infer/src/infer/relate/nll.rs b/compiler/rustc_infer/src/infer/relate/nll.rs
index 4cc6457df7a30..87a1ae7bbacaf 100644
--- a/compiler/rustc_infer/src/infer/relate/nll.rs
+++ b/compiler/rustc_infer/src/infer/relate/nll.rs
@@ -422,7 +422,7 @@ where
                 // Forbid inference variables in the RHS.
                 self.infcx
                     .dcx()
-                    .span_bug(self.delegate.span(), format!("unexpected inference var {b:?}",));
+                    .span_bug(self.delegate.span(), format!("unexpected inference var {b:?}"));
             }
             // FIXME(invariance): see the related FIXME above.
             _ => self.infcx.super_combine_consts(self, a, b),
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 95d55a7081db5..3f539945841b6 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -356,7 +356,9 @@ impl<'tcx> TyCtxt<'tcx> {
             }
 
             let Some(item_id) = self.associated_item_def_ids(impl_did).first() else {
-                self.dcx().span_bug(self.def_span(impl_did), "Drop impl without drop function");
+                self.dcx()
+                    .span_delayed_bug(self.def_span(impl_did), "Drop impl without drop function");
+                return;
             };
 
             if let Some((old_item_id, _)) = dtor_candidate {
diff --git a/compiler/rustc_middle/src/util/bug.rs b/compiler/rustc_middle/src/util/bug.rs
index dae6c0b9d68b8..a67ec99158210 100644
--- a/compiler/rustc_middle/src/util/bug.rs
+++ b/compiler/rustc_middle/src/util/bug.rs
@@ -42,7 +42,7 @@ fn opt_span_bug_fmt<S: Into<MultiSpan>>(
 /// delayed bug, so what is the point of this? It exists to help us test the interaction of delayed
 /// bugs with the query system and incremental.
 pub fn trigger_delayed_bug(tcx: TyCtxt<'_>, key: rustc_hir::def_id::DefId) {
-    tcx.dcx().span_bug(
+    tcx.dcx().span_delayed_bug(
         tcx.def_span(key),
         "delayed bug triggered by #[rustc_error(delayed_bug_from_inside_query)]",
     );
diff --git a/compiler/rustc_mir_build/src/build/expr/as_constant.rs b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
index d66540d8e79e4..a557f61b016bc 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_constant.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
@@ -110,12 +110,12 @@ fn lit_to_mir_constant<'tcx>(
     let LitToConstInput { lit, ty, neg } = lit_input;
     let trunc = |n| {
         let param_ty = ty::ParamEnv::reveal_all().and(ty);
-        let width = tcx
-            .layout_of(param_ty)
-            .map_err(|_| {
+        let width = match tcx.layout_of(param_ty) {
+            Ok(layout) => layout.size,
+            Err(_) => {
                 tcx.dcx().bug(format!("couldn't compute width of literal: {:?}", lit_input.lit))
-            })?
-            .size;
+            }
+        };
         trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
         let result = width.truncate(n);
         trace!("trunc result: {}", result);
diff --git a/compiler/rustc_mir_build/src/thir/constant.rs b/compiler/rustc_mir_build/src/thir/constant.rs
index 46580432f1328..65cc13286afc4 100644
--- a/compiler/rustc_mir_build/src/thir/constant.rs
+++ b/compiler/rustc_mir_build/src/thir/constant.rs
@@ -12,12 +12,12 @@ pub(crate) fn lit_to_const<'tcx>(
 
     let trunc = |n| {
         let param_ty = ParamEnv::reveal_all().and(ty);
-        let width = tcx
-            .layout_of(param_ty)
-            .map_err(|_| {
+        let width = match tcx.layout_of(param_ty) {
+            Ok(layout) => layout.size,
+            Err(_) => {
                 tcx.dcx().bug(format!("couldn't compute width of literal: {:?}", lit_input.lit))
-            })?
-            .size;
+            }
+        };
         trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
         let result = width.truncate(n);
         trace!("trunc result: {}", result);
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 676bc9db4a924..2f4da29133f1b 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -3681,9 +3681,9 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                 None
             }
             Res::SelfCtor(_) => {
-                // njn: remove comment?
                 // We resolve `Self` in pattern position as an ident sometimes during recovery,
-                // so delay a bug instead of ICEing.
+                // so delay a bug instead of ICEing. (Note: is this no longer true? We now ICE. If
+                // this triggers, please convert to a delayed bug and add a test.)
                 self.r.dcx().span_bug(
                     ident.span,
                     "unexpected `SelfCtor` in pattern, expected identifier"
diff --git a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
index 79f423756fd7a..189e1ba54bc36 100644
--- a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
+++ b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
@@ -62,11 +62,10 @@ pub fn is_const_evaluatable<'tcx>(
 
         match unexpanded_ct.kind() {
             ty::ConstKind::Expr(_) => {
-                // njn: ?
-                // FIXME(generic_const_exprs): we have a `ConstKind::Expr` which is fully concrete,
-                // but currently it is not possible to evaluate `ConstKind::Expr` so we are unable
-                // to tell if it is evaluatable or not. For now we just ICE until this is
-                // implemented.
+                // FIXME(generic_const_exprs): we have a fully concrete `ConstKind::Expr`, but
+                // haven't implemented evaluating `ConstKind::Expr` yet, so we are unable to tell
+                // if it is evaluatable or not. As this is unreachable for now, we can simple ICE
+                // here.
                 tcx.dcx().span_bug(span, "evaluating `ConstKind::Expr` is not currently supported");
             }
             ty::ConstKind::Unevaluated(uv) => {
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index 43f709352a293..cac5379674790 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -172,6 +172,8 @@ fn do_normalize_predicates<'tcx>(
     // the normalized predicates.
     let errors = infcx.resolve_regions(&outlives_env);
     if !errors.is_empty() {
+        // @lcnr: Let's still ICE here for now. I want a test case
+        // for that.
         tcx.dcx().span_bug(
             span,
             format!("failed region resolution while normalizing {elaborated_env:?}: {errors:?}"),
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index dc5b62fbd1c72..f8de19043e1bc 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -647,9 +647,7 @@ pub fn compute_inherent_assoc_ty_args<'a, 'b, 'tcx>(
         Err(_) => {
             tcx.dcx().span_bug(
                 cause.span,
-                format!(
-                    "{self_ty:?} was a subtype of {impl_ty:?} during selection but now it is not"
-                ),
+                format!("{self_ty:?} was equal to {impl_ty:?} during selection but now it is not"),
             );
         }
     }
@@ -1190,10 +1188,11 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
             ImplSource::Builtin(BuiltinImplSource::TraitUpcasting { .. }, _)
             | ImplSource::Builtin(BuiltinImplSource::TupleUnsizing, _) => {
                 // These traits have no associated types.
-                selcx.tcx().dcx().span_bug(
+                selcx.tcx().dcx().span_delayed_bug(
                     obligation.cause.span,
                     format!("Cannot project an associated type from `{impl_source:?}`"),
                 );
+                return Err(())
             }
         };
 
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
index a8d9b0f42d94e..d533e69a4fa7f 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
@@ -82,7 +82,7 @@ where
     let value = infcx.commit_if_ok(|_| {
         let ocx = ObligationCtxt::new(infcx);
         let value = op(&ocx).map_err(|_| {
-            infcx.dcx().span_bug(span, format!("error performing operation: {name}"))
+            infcx.dcx().span_delayed_bug(span, format!("error performing operation: {name}"))
         })?;
         let errors = ocx.select_all_or_error();
         if errors.is_empty() {
diff --git a/tests/ui/drop/missing-drop-method.rs b/tests/ui/drop/missing-drop-method.rs
new file mode 100644
index 0000000000000..5828fd6c06381
--- /dev/null
+++ b/tests/ui/drop/missing-drop-method.rs
@@ -0,0 +1,4 @@
+struct DropNoMethod;
+impl Drop for DropNoMethod {} //~ ERROR not all trait items implemented, missing: `drop`
+
+fn main() {}
diff --git a/tests/ui/drop/missing-drop-method.stderr b/tests/ui/drop/missing-drop-method.stderr
new file mode 100644
index 0000000000000..1128f33e627b3
--- /dev/null
+++ b/tests/ui/drop/missing-drop-method.stderr
@@ -0,0 +1,11 @@
+error[E0046]: not all trait items implemented, missing: `drop`
+  --> $DIR/missing-drop-method.rs:2:1
+   |
+LL | impl Drop for DropNoMethod {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `drop` in implementation
+   |
+   = help: implement the missing item: `fn drop(&mut self) { todo!() }`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0046`.