return an error instead of panicking (#419)

[guipublic]

Related issue(s)

Resolves #419

Description

Summary of changes

We return an error instead of unreachable!() when trying to compute with a non supported field operation

Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt with default settings.
• I have linked this PR to the issue(s) that it resolves.
• I have reviewed the changes on GitHub, line by line.
• I have ensured all changes are covered in the description.

Additional context

Note that the error is less user-friendly than the previous panic message, this is because errors with no location do not print the secondary message.

[jfecher]

let z: Field = 2 << 2;

I believe we've discussed previously that bitwise operations are unsupported in general on Fields and that this should be a type error. Let me know if my memory of this is correct. If so, I can put up a PR adding a more user friendly type error and suggest the user casts to an integer type beforehand as well.

[jfecher]

This should no longer be needed now that #687 is merged. I'd expect this condition to be unreachable for bitwise operators now but haven't tested thoroughly.

[kevaundray]

Closing as this has been handled on the frontend, so the ssa pass can assume that it won't ever happen