error[E0080]: evaluation of constant value failed
  --> tests/ui/guid_len.rs:12:14
   |
12 |     let _g = guid!("1234");
   |              ^^^^^^^^^^^^^ the evaluated program panicked at 'GUID string has wrong length (expected 36 bytes)', $DIR/tests/ui/guid_len.rs:12:14
   |
   = note: this error originates in the macro `guid` (in Nightly builds, run with -Z macro-backtrace for more info)