On 2019-01-24, Terry Reedy wrote:
Serhiy Storchaka suggested a compiler SyntaxWarning and uploaded a proof-of-concept diff that handled the above and many similar cases.
I believe that in general we should give better errors or warnings if we can do it without huge difficulty. Serhiy's patch is quite simple. The same check *could* be done by a linting tool. Putting it in CPython will make it more widely available. These checks could be helpful to beginners who probably won't have linting tools setup. I think we should not make it an error, otherwise we have changed Python "the language". We don't want to force other Python implementations to do the same check. It might be hard for them to implement. So, SyntaxWarning seems like a reasonable compromise. Regards, Neil