Anonymous """value-level""" servant API type definition

servant-valuelevel.hs

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TypeOperators #-}
import Data.Proxy
import GHC.TypeLits
import Servant.API

infixr 9 >:>
infixr 8 <||>

(>:>) :: Proxy a -> Proxy b -> Proxy (a :> b)
Proxy >:> Proxy = Proxy

(<||>) :: Proxy a -> Proxy b -> Proxy (a :<|> b)
Proxy <||> Proxy = Proxy

path
  :: KnownSymbol s
  => Proxy s
path = Proxy

capture
  :: KnownSymbol s
  => Proxy (Capture s a)
capture = Proxy

get
  :: Proxy (Get cts a)
get = Proxy

-- example

api = path @"hello" >:> capture @"userid" @Int >:> get @'[JSON] @String
 <||> path @"bye"   >:> capture @"userid" @Int >:> get @'[JSON] @String

-- and then call 'serve api ...' or 'docsFor api' or 'client api' or ...

{-
*Main λ> :t api
api
  :: Proxy
       (("hello" :> (Capture "userid" Int :> Get '[JSON] String))
        :<|> ("bye" :> (Capture "userid" Int :> Get '[JSON] String)))
-}