Change to ReError(ErrorGuaranteed)

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -368,7 +368,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
             | ty::ReVar(..)
             | ty::RePlaceholder(..)
             | ty::ReErased
-            | ty::ReError => None,
+            | ty::ReError(_) => None,
         }
     }
 

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -91,11 +91,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                     }
                     None => {
                         subst_regions.push(vid);
-                        infcx.tcx.sess.delay_span_bug(
+                        infcx.tcx.re_error_with_message(
                             concrete_type.span,
                             "opaque type with non-universal region substs",
-                        );
-                        infcx.tcx.lifetimes.re_error
+                        )
                     }
                 }
             };

compiler/rustc_borrowck/src/universal_regions.rs

@@ -821,7 +821,7 @@ impl<'tcx> UniversalRegionIndices<'tcx> {
     pub fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
         if let ty::ReVar(..) = *r {
             r.to_region_vid()
-        } else if let ty::ReError = *r {
+        } else if let ty::ReError(_) = *r {
             RegionVid::new(0)
         } else {
             *self

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -263,8 +263,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     // elision. `resolve_lifetime` should have
                     // reported an error in this case -- but if
                     // not, let's error out.
-                    tcx.sess.delay_span_bug(lifetime.ident.span, "unelided lifetime in signature");
-                    tcx.lifetimes.re_error
+                    tcx.re_error_with_message(lifetime.ident.span, "unelided lifetime in signature")
                 })
             }
         }
@@ -478,8 +477,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             debug!(?param, "unelided lifetime in signature");
 
                             // This indicates an illegal lifetime in a non-assoc-trait position
-                            tcx.sess.delay_span_bug(self.span, "unelided lifetime in signature");
-                            tcx.lifetimes.re_error
+                            tcx.re_error_with_message(self.span, "unelided lifetime in signature")
                         })
                         .into(),
                     GenericParamDefKind::Type { has_default, .. } => {
@@ -1623,7 +1621,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         } else {
                             err.emit();
                         }
-                        tcx.lifetimes.re_error
+                        tcx.re_error()
                     })
                 }
             })

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -786,13 +786,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
                     }
                     let Some(ty::ReEarlyBound(e)) = map.get(&region.into()).map(|r| r.expect_region().kind())
                     else {
-                        tcx
-                            .sess
-                            .delay_span_bug(
-                                return_span,
-                                "expected ReFree to map to ReEarlyBound"
-                            );
-                        return tcx.lifetimes.re_error;
+                        return tcx.re_error_with_message(return_span, "expected ReFree to map to ReEarlyBound")
                     };
                     tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
                         def_id: e.def_id,

compiler/rustc_hir_analysis/src/outlives/utils.rs

@@ -170,7 +170,7 @@ fn is_free_region(region: Region<'_>) -> bool {
         // ignore it. We can't put it on the struct header anyway.
         ty::ReLateBound(..) => false,
 
-        ty::ReError => false,
+        ty::ReError(_) => false,
 
         // These regions don't appear in types from type declarations:
         ty::ReErased | ty::ReVar(..) | ty::RePlaceholder(..) | ty::ReFree(..) => {

compiler/rustc_hir_analysis/src/variance/constraints.rs

@@ -409,7 +409,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
                 // way early-bound regions do, so we skip them here.
             }
 
-            ty::ReError => {}
+            ty::ReError(_) => {}
 
             ty::ReFree(..) | ty::ReVar(..) | ty::RePlaceholder(..) | ty::ReErased => {
                 // We don't expect to see anything but 'static or bound

compiler/rustc_infer/src/errors/note_and_explain.rs

@@ -31,7 +31,7 @@ impl<'a> DescriptionCtx<'a> {
 
             ty::RePlaceholder(_) => return None,
 
-            ty::ReError => return None,
+            ty::ReError(_) => return None,
 
             // FIXME(#13998) RePlaceholder should probably print like
             // ReFree rather than dumping Debug output on the user.

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -371,7 +371,7 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
 
             ty::ReStatic
             | ty::ReEarlyBound(..)
-            | ty::ReError
+            | ty::ReError(_)
             | ty::ReFree(_)
             | ty::RePlaceholder(..)
             | ty::ReErased => self.canonicalize_mode.canonicalize_free_region(self, r),

compiler/rustc_infer/src/infer/combine.rs

@@ -705,7 +705,7 @@ impl<'tcx> TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
                 return Ok(r);
             }
 
-            ty::ReError => {
+            ty::ReError(_) => {
                 return Ok(r);
             }
 
@@ -865,7 +865,7 @@ impl<'tcx> FallibleTypeFolder<'tcx> for ConstInferUnifier<'_, 'tcx> {
         match *r {
             // Never make variables for regions bound within the type itself,
             // nor for erased regions.
-            ty::ReLateBound(..) | ty::ReErased | ty::ReError => {
+            ty::ReLateBound(..) | ty::ReErased | ty::ReError(_) => {
                 return Ok(r);
             }
 

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -134,7 +134,7 @@ pub(super) fn note_and_explain_region<'tcx>(
 
         ty::RePlaceholder(_) => return,
 
-        ty::ReError => return,
+        ty::ReError(_) => return,
 
         // FIXME(#13998) RePlaceholder should probably print like
         // ReFree rather than dumping Debug output on the user.
@@ -315,7 +315,7 @@ pub fn unexpected_hidden_region_diagnostic<'tcx>(
                 )
             }
         }
-        ty::ReError => {
+        ty::ReError(_) => {
             err.delay_as_bug();
         }
         _ => {

compiler/rustc_infer/src/infer/freshen.rs

@@ -126,7 +126,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
             | ty::ReFree(_)
             | ty::ReVar(_)
             | ty::RePlaceholder(..)
-            | ty::ReError
+            | ty::ReError(_)
             | ty::ReErased => {
                 // replace all free regions with 'erased
                 self.tcx().lifetimes.re_erased

compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs

@@ -216,7 +216,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
                 Ok(self.tcx().lifetimes.re_static)
             }
 
-            ReError => Ok(self.tcx().lifetimes.re_error),
+            ReError(_) => Ok(self.tcx().re_error()),
 
             ReEarlyBound(_) | ReFree(_) => {
                 // All empty regions are less than early-bound, free,
@@ -438,7 +438,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
             }
             (VarValue::Value(a), VarValue::Empty(_)) => {
                 match *a {
-                    ReLateBound(..) | ReErased | ReError => {
+                    ReLateBound(..) | ReErased | ReError(_) => {
                         bug!("cannot relate region: {:?}", a);
                     }
 
@@ -467,7 +467,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
             }
             (VarValue::Empty(a_ui), VarValue::Value(b)) => {
                 match *b {
-                    ReLateBound(..) | ReErased | ReError => {
+                    ReLateBound(..) | ReErased | ReError(_) => {
                         bug!("cannot relate region: {:?}", b);
                     }
 
@@ -548,7 +548,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
                 );
             }
 
-            (ReError, _) | (_, ReError) => self.tcx().lifetimes.re_error,
+            (ReError(_), _) | (_, ReError(_)) => self.tcx().re_error(),
 
             (ReStatic, _) | (_, ReStatic) => {
                 // nothing lives longer than `'static`
@@ -1044,7 +1044,7 @@ impl<'tcx> LexicalRegionResolutions<'tcx> {
             ty::ReVar(rid) => match self.values[rid] {
                 VarValue::Empty(_) => r,
                 VarValue::Value(r) => r,
-                VarValue::ErrorValue => tcx.lifetimes.re_error,
+                VarValue::ErrorValue => tcx.re_error(),
             },
             _ => r,
         };

compiler/rustc_infer/src/infer/region_constraints/mod.rs

@@ -696,9 +696,11 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
 
     pub fn universe(&self, region: Region<'tcx>) -> ty::UniverseIndex {
         match *region {
-            ty::ReStatic | ty::ReErased | ty::ReFree(..) | ty::ReEarlyBound(..) | ty::ReError => {
-                ty::UniverseIndex::ROOT
-            }
+            ty::ReStatic
+            | ty::ReErased
+            | ty::ReFree(..)
+            | ty::ReEarlyBound(..)
+            | ty::ReError(_) => ty::UniverseIndex::ROOT,
             ty::RePlaceholder(placeholder) => placeholder.universe,
             ty::ReVar(vid) => self.var_universe(vid),
             ty::ReLateBound(..) => bug!("universe(): encountered bound region {:?}", region),

compiler/rustc_middle/src/ty/context.rs

@@ -275,9 +275,6 @@ pub struct CommonLifetimes<'tcx> {
 
     /// Erased region, used outside of type inference.
     pub re_erased: Region<'tcx>,
-
-    /// Error region, used only for error reporting.
-    pub re_error: Region<'tcx>,
 }
 
 pub struct CommonConsts<'tcx> {
@@ -327,11 +324,7 @@ impl<'tcx> CommonLifetimes<'tcx> {
             ))
         };
 
-        CommonLifetimes {
-            re_static: mk(ty::ReStatic),
-            re_erased: mk(ty::ReErased),
-            re_error: mk(ty::ReError),
-        }
+        CommonLifetimes { re_static: mk(ty::ReStatic), re_erased: mk(ty::ReErased) }
     }
 }
 
@@ -656,6 +649,27 @@ impl<'tcx> TyCtxt<'tcx> {
         self.mk_ty(Error(reported))
     }
 
+    /// Constructs a `RegionKind::ReError` lifetime and registers a `delay_span_bug` to ensure it
+    /// gets used.
+    #[track_caller]
+    pub fn re_error(self) -> Region<'tcx> {
+        self.re_error_with_message(
+            DUMMY_SP,
+            "RegionKind::ReError constructed but no error reported",
+        )
+    }
+
+    /// Constructs a `RegionKind::ReError` lifetime and registers a `delay_span_bug` with the given
+    /// `msg` to ensure it gets used.
+    #[track_caller]
+    pub fn re_error_with_message<S: Into<MultiSpan>>(self, span: S, msg: &str) -> Region<'tcx> {
+        let reported = self.sess.delay_span_bug(span, msg);
+        let r = ty::ReError(reported);
+        Region(Interned::new_unchecked(
+            self.interners.region.intern(r, |r| InternedInSet(self.interners.arena.alloc(r))).0,
+        ))
+    }
+
     /// Like [TyCtxt::ty_error] but for constants, with current `ErrorGuaranteed`
     #[track_caller]
     pub fn const_error_with_guaranteed(

compiler/rustc_middle/src/ty/generics.rs

@@ -100,7 +100,7 @@ impl GenericParamDef {
         preceding_substs: &[ty::GenericArg<'tcx>],
     ) -> ty::GenericArg<'tcx> {
         match &self.kind {
-            ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_error.into(),
+            ty::GenericParamDefKind::Lifetime => tcx.re_error().into(),
             ty::GenericParamDefKind::Type { .. } => tcx.ty_error().into(),
             ty::GenericParamDefKind::Const { .. } => {
                 tcx.const_error(tcx.bound_type_of(self.def_id).subst(tcx, preceding_substs)).into()

compiler/rustc_middle/src/ty/opaque_types.rs

@@ -109,7 +109,7 @@ impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
             // them.
             ty::ReErased => return r,
 
-            ty::ReError => return r,
+            ty::ReError(_) => return r,
 
             // The regions that we expect from borrow checking.
             ty::ReEarlyBound(_) | ty::ReFree(_) => {}
@@ -140,7 +140,7 @@ impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
                     )
                     .emit();
 
-                self.tcx().lifetimes.re_error
+                self.tcx().re_error()
             }
         }
     }

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -2114,7 +2114,7 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
 
             ty::ReVar(_) if identify_regions => true,
 
-            ty::ReVar(_) | ty::ReErased | ty::ReError => false,
+            ty::ReVar(_) | ty::ReErased | ty::ReError(_) => false,
 
             ty::ReStatic => true,
         }
@@ -2194,7 +2194,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
             }
             ty::ReVar(_) => {}
             ty::ReErased => {}
-            ty::ReError => {}
+            ty::ReError(_) => {}
             ty::ReStatic => {
                 p!("'static");
                 return Ok(self);

compiler/rustc_middle/src/ty/sty.rs

@@ -1623,13 +1623,13 @@ impl<'tcx> Region<'tcx> {
             ty::ReVar(..) => false,
             ty::RePlaceholder(placeholder) => placeholder.name.is_named(),
             ty::ReErased => false,
-            ty::ReError => false,
+            ty::ReError(_) => false,
         }
     }
 
     #[inline]
     pub fn is_error(self) -> bool {
-        matches!(*self, ty::ReError)
+        matches!(*self, ty::ReError(_))
     }
 
     #[inline]
@@ -1692,7 +1692,7 @@ impl<'tcx> Region<'tcx> {
             ty::ReErased => {
                 flags = flags | TypeFlags::HAS_RE_ERASED;
             }
-            ty::ReError => {}
+            ty::ReError(_) => {}
         }
 
         debug!("type_flags({:?}) = {:?}", self, flags);

compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs

@@ -299,7 +299,7 @@ fn encode_region<'tcx>(
         RegionKind::ReEarlyBound(..)
         | RegionKind::ReFree(..)
         | RegionKind::ReStatic
-        | RegionKind::ReError
+        | RegionKind::ReError(_)
         | RegionKind::ReVar(..)
         | RegionKind::RePlaceholder(..) => {
             bug!("encode_region: unexpected `{:?}`", region.kind());

compiler/rustc_traits/src/chalk/lowering.rs

@@ -493,7 +493,7 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::Lifetime<RustInterner<'tcx>>> for Region<'t
             ty::ReEarlyBound(_) => {
                 panic!("Should have already been substituted.");
             }
-            ty::ReError => {
+            ty::ReError(_) => {
                 panic!("Error lifetime should not have already been lowered.");
             }
             ty::ReLateBound(db, br) => chalk_ir::LifetimeData::BoundVar(chalk_ir::BoundVar::new(