Import a data constructor of a related data type

Question

I am using GHC 7.10.2. There is a class type RenderRoutein yesodwhich is as follows:

class Eq (Route a) => RenderRoute a where
  data Route a
  renderRoute :: Route a -> ([Text], [(Text, Text)])

I wrote an instance in a module with a name Yesod.Crudthat looks like this:

data Crud master p c = Crud { ... }
instance (PathPiece (Key c), Eq (Key c), PathPiece p, Eq p) => RenderRoute (Crud master p c) where
  data Route (Crud master p c)
    = EditR (Key c)
    | DeleteR (Key c)
    | IndexR p
    | AddR p
    | ViewR (Key c)

If somewhere else I import everything using this

import Yesod.Crud

then five data constructors belonging to my associated data type are in scope. I am trying to figure out how to write an import statement in a more restrictive way. Say that I only want to add ViewRto the scope (and probably the data type Crud). If i try

import Yesod.Crud (ViewR)

Then the GHC errors with the following:

src/Import/Base.hs:9:55:
    In module ‘Yesod.Crud’:
      ‘ViewR’ is a data constructor of ‘Route’
    To import it use
      ‘import’ Yesod.Crud( Route( ViewR ) )
    or
      ‘import’ Yesod.Crud( Route(..) )

If I try the first sentence, these are errors with

src/Import/Base.hs:10:46:
    Module ‘Yesod.Crud’ does not export ‘Route(ViewR)’

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