Use of named constants in contracts with bit_vector solver

[rod-chapman]

It appears that named constants do not work in contracts when the bit_vector solver is specified.
For example, I have

const Q         : i32 = 3329;

then

assert(3329 >> 1 == 1664) by (bit_vector);

works fine, but

assert(Q >> 1 == 1664) by (bit_vector);

is rejected with

error: unsupported for bit-vector: expression conversion Call(Fun(Fun(Path(Some("lib"), ["Q"])), None), [], [])
   --> src/lib.rs:335:10
    |
335 |   assert(Q >> 1 == 1664) by (bit_vector);
    |          ^

Can this usage be supported please?