error[E0080]: evaluation of `<A<()> as Foo<()>>::BAR` failed
  --> $DIR/issue-50814-2.rs:14:24
   |
LL |     const BAR: usize = [5, 6, 7][T::BOO];
   |                        ^^^^^^^^^^^^^^^^^ index out of bounds: the length is 3 but the index is 42

note: erroneous constant encountered
  --> $DIR/issue-50814-2.rs:18:6
   |
LL |     &<A<T> as Foo<T>>::BAR
   |      ^^^^^^^^^^^^^^^^^^^^^

note: the above error was encountered while instantiating `fn foo::<()>`
  --> $DIR/issue-50814-2.rs:30:22
   |
LL |     println!("{:x}", foo::<()>() as *const usize as usize);
   |                      ^^^^^^^^^^^

error: aborting due to previous error

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