UnusedDctorImport Warning

Example

module ShortFailingExample where

import Data.Maybe (Maybe(..))

test :: forall a. Maybe a -> Int
test _ = 42

Cause

A module is imported with an explicit imports list including a type with data construtors (Maybe(..) in this example) but only the type constructor and not its data constructors are used.

Fix

Import only the type without data constructors. In the above example:

import Data.Maybe (Maybe)

Notes

This error is auto-fixable.