Funny behavior of IDLE 3.7.0

[Chris Angelico]

On Wed, Nov 13, 2019 at 3:57 AM Terry Reedy <tjreedy at udel.edu> wrote:
>
> On 11/12/2019 8:29 AM, Chris Angelico wrote:
>
> > The OP said that the equals sign in the *first* line was flagged as
> > invalid syntax. Implication being that the error is being reported on
> > the line "i = 4", not on the print at the end. And in fact, I can
> > confirm this. Run | Check Module reports an error where i is assigned
> > to. Here's how it looks in command-line Python:
> >
> > $ python3.7 demo.py
> >    File "<fstring>", line 1
> >      (i=)
> >        ^
> > SyntaxError: invalid syntax
> >
> > Newer Pythons are happy with this example, but if you replace the
> > error with something else - say, f'{i+}' - then the same phenomenon
> > occurs. Command-line Python reports the error on line 1 of
> > "<fstring>", and Idle misinterprets that as line 1 of the original
> > file.
> >
> > This looks like an error reporting flaw in f-string handling.
>
> Can you open a bug issue (if not one already) and nosy me?
> This is awful for any IDE that processes error messages.
>
> Replacing {} with () is a secondary bug.  The actual code
>    {i=}
> would be clearer, and make it easier for an IDE to search for the real line.
>

I can do that, but I actually think the correct fix isn't inside Idle.
See the followup regarding the difference between SyntaxError and
NameError; in the latter case, the error is more usefully reported.

ChrisA