constraint_proof_bug_lib.m:050: In instance declaration for
constraint_proof_bug_lib.m:050:   `constrainable(code)':
constraint_proof_bug_lib.m:050:   the first instance type
constraint_proof_bug_lib.m:050:   `constraint_proof_bug_lib.code' is an
constraint_proof_bug_lib.m:050:   abstract exported equivalence type.