Commit e34e30e4 authored by Andrew Martin's avatar Andrew Martin Committed by Ben Gamari

Warn against using Data.Monoid.First

Noting that it will be removed in the future.
parent 358b5080
......@@ -88,6 +88,16 @@ import Data.Semigroup.Internal
--
-- >>> getFirst (First (Just "hello") <> First Nothing <> First (Just "world"))
-- Just "hello"
--
-- Use of this type is discouraged. Note the following equivalence:
--
-- > Data.Monoid.First x === Maybe (Data.Semigroup.First x)
--
-- In additional to being equivalent in the structural sense, the two
-- also have 'Monoid' instances that behave the same. This type will
-- be marked deprecated in GHC 8.8. It will be removed in GHC 8.10.
-- Users are advised to use the variant from "Data.Semigroup" and wrap
-- it in 'Maybe'.
newtype First a = First { getFirst :: Maybe a }
deriving ( Eq -- ^ @since 2.01
, Ord -- ^ @since 2.01
......
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