Remove unused enum variant

Author: oli-obk

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

@@ -386,21 +386,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
                         self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
                     }
-
-                    RegionResolutionError::MemberConstraintFailure {
-                        hidden_ty,
-                        member_region,
-                        span,
-                    } => {
-                        let hidden_ty = self.resolve_vars_if_possible(hidden_ty);
-                        unexpected_hidden_region_diagnostic(
-                            self.tcx,
-                            span,
-                            hidden_ty,
-                            member_region,
-                        )
-                        .emit();
-                    }
                 }
             }
         }
@@ -438,8 +423,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             RegionResolutionError::GenericBoundFailure(..) => true,
             RegionResolutionError::ConcreteFailure(..)
             | RegionResolutionError::SubSupConflict(..)
-            | RegionResolutionError::UpperBoundUniverseConflict(..)
-            | RegionResolutionError::MemberConstraintFailure { .. } => false,
+            | RegionResolutionError::UpperBoundUniverseConflict(..) => false,
         };
 
         let mut errors = if errors.iter().all(|e| is_bound_failure(e)) {
@@ -454,7 +438,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             RegionResolutionError::GenericBoundFailure(ref sro, _, _) => sro.span(),
             RegionResolutionError::SubSupConflict(_, ref rvo, _, _, _, _) => rvo.span(),
             RegionResolutionError::UpperBoundUniverseConflict(_, ref rvo, _, _, _) => rvo.span(),
-            RegionResolutionError::MemberConstraintFailure { span, .. } => span,
         });
         errors
     }

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

@@ -19,7 +19,6 @@ use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::ty::{ReEarlyBound, ReEmpty, ReErased, ReFree, ReStatic};
 use rustc_middle::ty::{ReLateBound, RePlaceholder, ReVar};
 use rustc_middle::ty::{Region, RegionVid};
-use rustc_span::Span;
 use std::fmt;
 
 /// This function performs lexical region resolution given a complete
@@ -108,11 +107,6 @@ pub enum RegionResolutionError<'tcx> {
         SubregionOrigin<'tcx>, // cause of the constraint
         Region<'tcx>,          // the placeholder `'b`
     ),
-
-    /// Indicates a failure of a `MemberConstraint`. These arise during
-    /// impl trait processing explicitly -- basically, the impl trait's hidden type
-    /// included some region that it was not supposed to.
-    MemberConstraintFailure { span: Span, hidden_ty: Ty<'tcx>, member_region: Region<'tcx> },
 }
 
 struct RegionAndOrigin<'tcx> {