char_inst.m:017: In clause for `main(di, uo)':
char_inst.m:017:   in argument 1 of call to predicate `char_inst.test'/3:
char_inst.m:017:   mode error: variable `V_8' has instantiatedness
char_inst.m:017:   `unique('x')',
char_inst.m:017:   expected instantiatedness was
char_inst.m:017:     named inst key_char
char_inst.m:017:     which expands to
char_inst.m:017:       bound(
char_inst.m:017:         f
char_inst.m:017:       ;
char_inst.m:017:         i
char_inst.m:017:       ;
char_inst.m:017:         s
char_inst.m:017:       ).