Delete Rvalue::Len

Everything's moved to `PtrMetadata` instead.

compiler/rustc_borrowck/src/lib.rs

@@ -820,7 +820,6 @@ use self::ReadOrWrite::{Activation, Read, Reservation, Write};
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 enum ArtificialField {
-    ArrayLength,
     FakeBorrow,
 }
 
@@ -1268,16 +1267,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                 );
             }
 
-            &(Rvalue::Len(place) | Rvalue::Discriminant(place)) => {
-                let af = match *rvalue {
-                    Rvalue::Len(..) => Some(ArtificialField::ArrayLength),
-                    Rvalue::Discriminant(..) => None,
-                    _ => unreachable!(),
-                };
+            &Rvalue::Discriminant(place) => {
                 self.access_place(
                     location,
                     (place, span),
-                    (Shallow(af), Read(ReadKind::Copy)),
+                    (Shallow(None), Read(ReadKind::Copy)),
                     LocalMutationIsAllowed::No,
                     state,
                 );