I made a working patch, but we need to figure out the details.

As the patch introduces new non-obvious name to the base library, I’m starting a thread in libraries@ to figure out community's opinion.

I’m proposing to add `type family (n :: Symbol) <> (m :: Symbol)` to `GHC.TypeLits`.

Currently implementation uses (<>). Another options are (++), (+++) or `AppendSymbol`.

- (<>) resembles Semigroup operation, as (+) resembles Num operation

- (++) is a list appending operation. IMHO it’s a bad choice

- (+++) is used by ghc-typelits-symbols plugin

- `AppendSymbol` is sensible too, if libraries want to define own versions of type-level (<>) (e.g. polykinded)

Discussion period: 2 weeks.

Cheers,

Oleg Grenrus.

- [2] https://github.com/konn/ghc-typelits-symbols/blob/cd812f4cfc2e6816a18283a6a0e9bb2d9ea2905e/src/GHC/TypeLits/Symbols/Internal.hs#L6-L8