[Sqlalchemy-tickets] Issue #3969: negation of labeled element? (zzzeek/sqlalchemy)

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

New issue 3969: negation of labeled element?
https://bitbucket.org/zzzeek/sqlalchemy/issues/3969/negation-of-labeled-element

Michael Bayer:

this is technically something that semantically doesn't make sense, but in the "what I expect" category it does, which is to negate the inner element of a label.


```
#!python

from sqlalchemy import *

expr = or_(column('x') == 1, column('y') == 2)

bug = not_(expr.label('foo'))

from sqlalchemy.dialects import sqlite

print bug.compile()
print bug.compile(dialect=sqlite.dialect())

```

```
#!


NOT x = :x_1 OR y = :y_1
x = ? OR y = ? = 0
```

so the parenthesis are lost because we don't unwrap the label(), and we in fact hit a rule in ColumnElement._negate() where it assumes we're negating a true/false, so for a non-native-boolean it then sticks on "= 0" to the whole thing to make things worse.