base constructors: 
++d_: 1
bmc
++b_: 1

base(), b, cb: 
rref: ++b_: 1
lref: ++b_: 1
const lref: b_: 1

base assignments: 
bcc
bca
bma
++b_: 1
bma

derived constructors: 
++d_: 1
++d_: 1

derived(), d, cd: 
rref: ++d_: 1
lref: ++d_: 2
const lref: d_: 1

derived assignments: 
bcc
dcc
bca
dca
bma
dma
++d_: 1
bma
dma

slicing assignments: 
bca
bma
++d_: 1
bma