error[E0503]: cannot use `y` because it was mutably borrowed
  --> $DIR/borrowck-anon-fields-variant.rs:16:19
   |
LL |       Foo::Y(ref mut a, _) => a,
   |              --------- borrow of `y.0` occurs here
...
LL |     let b = match y {
   |                   ^ use of borrowed `y.0`
...
LL |     *a += 1;
   |     ------- borrow later used here

error[E0503]: cannot use `y` because it was mutably borrowed
  --> $DIR/borrowck-anon-fields-variant.rs:34:19
   |
LL |       Foo::Y(ref mut a, _) => a,
   |              --------- borrow of `y.0` occurs here
...
LL |     let b = match y {
   |                   ^ use of borrowed `y.0`
...
LL |     *a += 1;
   |     ------- borrow later used here

error[E0499]: cannot borrow `y.0` as mutable more than once at a time
  --> $DIR/borrowck-anon-fields-variant.rs:36:14
   |
LL |       Foo::Y(ref mut a, _) => a,
   |              --------- first mutable borrow occurs here
...
LL |       Foo::Y(ref mut b, _) => b,
   |              ^^^^^^^^^ second mutable borrow occurs here
...
LL |     *a += 1;
   |     ------- first borrow later used here

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0499, E0503.
For more information about an error, try `rustc --explain E0499`.