error[E0080]: evaluation of constant value failed
  --> tests/ui/guid_hex.rs:12:14
   |
12 |     let _g = guid!("g1234567-89ab-cdef-0123-456789abcdef");
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'GUID string contains one or more invalid characters', $DIR/tests/ui/guid_hex.rs:12:14
   |
   = note: this error originates in the macro `guid` (in Nightly builds, run with -Z macro-backtrace for more info)