[Python-Dev] Can Python implementations reject semantically invalid expressions?

[Nick Coghlan]

On Fri, Jul 2, 2010 at 4:55 PM, Craig Citro <craigcitro at gmail.com> wrote:
> Honestly, though, I'd come down on the side of letting the compiler
> raise an error -- while I understand that it means you have
> *different* behavior, I think it's *preferable* behavior.

But you would be taking a module that will compile and making it uncompilable.

The Python code:

  def f():
    return 1 + "1"

has fully defined runtime semantics: when f() is called, it will raise
TypeError. A module containing this code is still perfectly valid
Python (e.g. the Python test suite does that kind of thing a lot in
tests of the core interpreter semantics).

A Python implementation issuing a SyntaxWarning over this would be
fine, but triggering a SyntaxError would not be valid. However, I'd be
inclined to leave this kind of check to tools like pychecker and
pylint.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia