Support for Type Families

[newhoggy]

At the moment, type families look like a regular type constructor. For example, in the following tooltip in HLS:

It is non-obvious that AuxiliaryData is a type family.

If there was some visual cue that AuxiliaryData is a type family, for example by being rendered in a different colour, then the type would be much easier to understand.

Even better would be if the type family was expanded. For example while type above is shown to be Maybe (AuxiliaryData (ShelleyLedgerEra era)), the type below could be expanded to say what the type is after type family application, which is to
Maybe (Metadata (ShelleyEra StandardCrypto))

Even more better would be if I could see each step of type family application:

Maybe (AuxiliaryData (ShelleyLedgerEra era))
Maybe (AuxiliaryData (ShelleyEra StandardCrypto))
Maybe (AuxiliaryData StandardShelley)
Maybe (Metadata (ShelleyEra StandardCrypto))

[googleson78]

Actually there is a case where this does currently work - when asking for the type of a term in a function body - it will display the declared (type family) type, and the "current" one, at the point at which you asked for it.

[michaelpj]

I think we'd need semantic highlighting to make it look different. That needs some work in the lsp library and then we'd have to use it in HLS. So not totally trivial but something we should take advantage of at some point.

[soulomoon]

We have semantic highlighting now. should be easy to differ them now. If they are in the source code.