Pre-SIP: better strictEquality support in pattern matching

[soronpo]

I suggest you add links to previous discussions:

Enumeration does not derive `CanEqual` for `strictEquality`

What is the reason enumeration does not derive CanEqual? It was very surprising that this is not the default case, which led me to submit the following issue: However, only after I noticed that the test cases explicitly check the interaction of enums and strictEquality, I understood that this is an intended design decision.