[bug] Generics not supported

[bsnelson]

🐞Bug Report

Bug Description

Gremlins does not support generics, which were added to Go as of 1.18. Specifically the union operator ("|") allows type constraints to contain multiple types. Gremlins incorrectly labels this as an INVERT_BITWISE operation and declares it "NOT COVERED" regardless of tests.

To Reproduce

Steps to reproduce the behavior:

1. Create a trivial go program that uses a type interface with union, e.g.:
   type IntorString interface { ~int | ~string }
2. Create a test file that tests the program
3. Create a .gremlins.yml as thus:
   unleash:
   mutants:
   invert-bitwise:
   enabled: true
4. Execute gremlins unleash
5. Result will contain:
   NOT COVERED INVERT_BITWISE at ....

Expected behaviour

Gremlins will ignore the | characters, as they are not bitwise operators in this context

Screenshots

Operating System

Should be platform agnostic

Additional Context