[Sqlalchemy-tickets] Issue #3170: use of singletons in 0.9 causes non-intuitive folding of constants (zzzeek/sqlalchemy)

[Mike B. <iss...@bi...>]

New issue 3170: use of singletons in 0.9 causes non-intuitive folding of constants
https://bitbucket.org/zzzeek/sqlalchemy/issue/3170/use-of-singletons-in-09-causes-non

Mike Bayer:


```
#!python

from sqlalchemy import select, null

from sqlalchemy.sql.elements import Null

print select([null(), null()])

print select([Null(), Null()])

```

```
#!sql


SELECT NULL AS anon_1
SELECT NULL AS anon_1, NULL AS anon_2
```

this is due to the singleton.

it's totally a regression, so this is critical that something is figured out.