In this case I agree that a SyntaxWarning is a good idea, per Serhiy's patch. I would be even more conservative, and only warn if the first object is a tuple -- the case of the missing comma in the original example appears likely enough, but I don't expect people to write e.g. `[[1, 2], (3, 4)]` very often, so leaving the comma out there would be very unlikely.
Regarding the issue of when it's appropriate to issue a SyntaxWarning vs. when to leave it up to linters, again I would recommend great caution and only warn about code that is *definitely* going to fail when executed. (Or at least is *definitely* not going to please the programmer -- one of the first cases where we added a SyntaxWarning was actually `assert(condition, message)`, which "fails" by never failing. :-) But this is one of those cases. On Thu, Jan 24, 2019 at 2:10 PM Neil Schemenauer <nas-pyt...@arctrix.com> wrote: > 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 > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/guido%40python.org > -- --Guido van Rossum (python.org/~guido)
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