Choose.purs

module Choose where

import Prelude

import Data.Symbol (class IsSymbol, SProxy, reflectSymbol)
import Data.Variant (Variant)
import Data.Variant.Internal (VariantRep(..))
import Prim.Row (class Cons)
import Record.Unsafe (unsafeGet)
import Unsafe.Coerce (unsafeCoerce)

data HasField (r :: # Type) = HasField String

hasField :: forall s a r' r. IsSymbol s => Cons s a r' r => SProxy s -> HasField r
hasField s = HasField $ reflectSymbol s

choose :: forall r. HasField r -> Record r -> Variant r
choose (HasField k) r = coerceV $ VariantRep { type: k, value: unsafeGet k r }
  where
  coerceV :: forall a. VariantRep a -> Variant r
  coerceV = unsafeCoerce