error[E0601]: `main` function not found in crate `$CRATE`
  --> tests/compile-fail/panic-when-reading-fields-of-tracked-structs-from-older-revisions.rs:46:2
   |
46 | }
   |  ^ consider adding a `main` function to `$DIR/tests/compile-fail/panic-when-reading-fields-of-tracked-structs-from-older-revisions.rs`