Check for collisions about mitx-grading-library

[ChristopherChudzicki]

We can check for variable--constant collisions and variable--variable collisions. I don't think we can check for constant--constant or function--function collisions without changing how constants and functions are declared because unlike variables, they are declared using dictionaries and Python dictionary literals permit duplicate keys and use the latest:

{
    'a': 5,
    'a': 10
} ==
{
    'a': 10
}
# True

Regarding

We've decided that users should be able to overwrite default constants and functions, however.

Another thing we could do is raise an error (ConfigCollisionError, or something) with a message like "ConfigCollisionError: Declaring variable 'i' will overwrite existing constant 'i'. To proceed anyway, add suppress_warnings=True to your grader configuration. Seems like it could be a useful pattern in other cases, too.

[jolyonb]

Ah. Good point. Less work for us then! Let's just do variable-variable and variable-constant checks.

I'm happy to greenlight a warning message like that. Let's call it ConfigCollisionWarning. Putting in suppress_warnings=True will be annoying, but then again, that's kind of the point.

[ChristopherChudzicki]

Ok! I'll do it now.

[ChristopherChudzicki]

resolved by #53