error[E0080]: could not evaluate enum discriminant
  --> $DIR/const-err4.rs:18:11
   |
LL |     Boo = [unsafe { Foo { b: () }.a }; 4][3],
   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ attempted to read undefined bytes

error: aborting due to previous error

For more information about this error, try `rustc --explain E0080`.