x=int,y=int,z=absent,s=absent
x=int,y=empty,z=absent,s=absent
x=empty,y=int,z=absent,s=absent
x=empty,y=empty,z=absent,s=absent
a=1,y=int,x=absent,z=absent,s=absent
a=1,y=empty,x=absent,z=absent,s=absent
a=,y=int,x=absent,z=absent,s=absent
a=,y=empty,x=absent,z=absent,s=absent
x=int,b=2,y=absent,z=absent,s=absent
x=int,b=,y=absent,z=absent,s=absent
x=empty,b=2,y=absent,z=absent,s=absent
x=empty,b=,y=absent,z=absent,s=absent
