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`HiddenConstructors` Warning

errors/HiddenConstructors.md

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HiddenConstructors Warning

Example

purescript
module ShortFailingExample (N) where

import Data.Newtype (class Newtype)
import Data.Generic.Rep (class Generic)

newtype N a = MkN a

derive instance newtypeN :: Newtype (N a) _
derive instance genericN :: Generic (N a) _

Cause

Instances of Newtype and Generic allow to match values of their type with unwrap and from, and to construct them with wrap or to hence making the constructors public.

Fix

  • Export the constructors:
diff
-module ShortFailingExample (N) where
+module ShortFailingExample (N(..)) where
  • or remove the instances:
diff
 module ShortFailingExample (N) where

-import Data.Newtype (class Newtype)
-import Data.Generic.Rep (class Generic)

 newtype N a = MkN a

-derive instance newtypeN :: Newtype (N a) _
-derive instance genericN :: Generic (N a) _