[issue9011] ast_for_factor unary minus optimization changes AST

[Mark Dickinson]

Mark Dickinson <dickinsm at gmail.com> added the comment:

N.B.  That if block isn't pure optimization:  removing it gives a minor change in behaviour:

Currently (Python 2.7, on a 64-bit machine):

>>> -9223372036854775808
-9223372036854775808

And with the optimization removed:

>>> -9223372036854775808
-9223372036854775808L

I actually consider the second behaviour more correct than the first, since it follows clearly from the language rules (numeric literals have no sign, so the above *should* be interpreted as the unary minus operator applied to a literal, and that literal really is a PyLong).  But obviously the contributors to issue 1441486 either disagree, or didn't want to introduce a regression from 2.4.

I still consider that removing that if block is the right thing to do for 2.7.  The change in behaviour really shouldn't affect any reasonable code---anywhere that an int is acceptable, a long should be too.



Neil, any comments?

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nosy: +nascheme
priority: normal -> high

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<http://bugs.python.org/issue9011>
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