Add Cardano.Base.Typeable with type TypeName a

cardano-base/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## 0.1.4.0
 
+* Add `Cardano.Base.Typeable` module with type `TypeName a` and its `IsString` and `Show` instances.
 * Add a workaround for QuickCheck >= 2.18 replacing `withMaxSuccess`
   with `withNumTests` and deprecating the former.
 

cardano-base/cardano-base.cabal

@@ -44,6 +44,7 @@ library
     Cardano.Base.FeatureFlags
     Cardano.Base.IP
     Cardano.Base.Proxy
+    Cardano.Base.Typeable
 
   build-depends:
     aeson,

cardano-base/src/Cardano/Base/Typeable.hs

@@ -0,0 +1,23 @@
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE LambdaCase #-}
+
+-- | Wrapper for Data.Typeable, plus convenience functions
+module Cardano.Base.Typeable (
+  module X,
+  TypeName (..),
+) where
+
+import Data.String (IsString (fromString))
+import Data.Typeable as X
+
+data TypeName a where
+  TypeNameString :: String -> TypeName a
+  TypeName :: Typeable a => TypeName a
+
+instance IsString (TypeName a) where
+  fromString = TypeNameString
+
+instance Show (TypeName a) where
+  show = \case
+    TypeNameString name -> name
+    t@(TypeName {}) -> show (typeRep t)