No error or warning on duplicate CompiledName

[kerams]

https://fable.io/repl/#?code=C4TwDgpgBAGlC8BYAUFNUA+UDaAeAwgPYC2YAlgDYQAmAcgIbHQBEAZq8wHwC6UAginSYcBEuSp1GLdl14AhIA&html=Q&css=Q

type X =
    | [<CompiledName "ff">] A
    | [<CompiledName "ff">] B

Fable, unlike .NET, honours this attribute on union cases. However, it doesn't verify that the names are unique. At the very least I would like to see a warning if there are valid use cases for this, otherwise an error.

[MangelMaxime]

I am almost certain that I saw some JavaScript libraries that used different value of enum to map to the same value.

In those scenarios it is normal case and does not need a warning or error message as they would be false positive.

Because of that I am unsure if this is something we can improve.

[kerams]

You can disable a warning, but you can't conjure one out of thin air:). I am starting to make heavy use of CompiledName and I want compile-time assurance that I didn't make a mistake in duplicating labels.

[MangelMaxime]

You can disable a warning, but you can't conjure one out of thin air

Fable does not have this feature (yet)

Also, I confused CompiledName with CompiledValue which is something else.

And indeed, I think have 2 enum cases name being the same is probably strange and should be reported as error. If there are issues with that in the future, we can reduce it to a warning.