BUG: Unable to add column based on a scalar parameter

[seibs]

If I first cast the parameter to a different type, the expression compiles.

For example, this works

param = ibis.param('timestamp', name='param')
table.mutate(param=param.cast('date')).compile(params={param: '2017-02-01'})

but, this fails

param = ibis.param('timestamp', name='param')
table.mutate(param=param).compile(params={param: '2017-02-01'})

[cpcloud]

Thanks, will take a look