of columns given positionally would not be preserved. This could
have potential impact in positional situations such as applying the
resulting :class:`.TextAsFrom` object to a union.
Have also considered linking column.label() to the "column" itself being
in the result map but this reveals some naming collision problems (that
also seem to be very poorly tested...). This should be as far as
we want to go right now with [ticket:2932].
more flexible ways to set up bound parameters and return types;
in particular, a :func:`.text` can now be turned into a full
FROM-object, embeddable in other statements as an alias or CTE
using the new method :meth:`.TextClause.columns`.
[ticket:2877]
Mike Bayer