GHC 9.4: warning about missing LANGUAGE TypeOperators

[andreasabel]

This warning can be fixed in a backwards-compatible way by adding TypeOperators to default-extensions: in the .cabal file.

Building library for dlist-1.0..
[1 of 5] Compiling Data.DList.Internal ( Data/DList/Internal.hs, dist/build/Data/DList/Internal.o, dist/build/Data/DList/Internal.dyn_o )

Data/DList/Internal.hs:642:12: warning: [-Wtype-equality-requires-operators]
    The use of ‘~’ without TypeOperators
    will become an error in a future GHC release.
    Suggested fix: Perhaps you intended to use TypeOperators
    |
642 | instance a ~ Char => IsString (DList a) where
    |            ^
[2 of 5] Compiling Data.DList       ( Data/DList.hs, dist/build/Data/DList.o, dist/build/Data/DList.dyn_o )
[3 of 5] Compiling Data.DList.DNonEmpty.Internal ( Data/DList/DNonEmpty/Internal.hs, dist/build/Data/DList/DNonEmpty/Internal.o, dist/build/Data/DList/DNonEmpty/Internal.dyn_o )

Data/DList/DNonEmpty/Internal.hs:459:12: warning: [-Wtype-equality-requires-operators]
    The use of ‘~’ without TypeOperators
    will become an error in a future GHC release.
    Suggested fix: Perhaps you intended to use TypeOperators
    |
459 | instance a ~ Char => IsString (DNonEmpty a) where
    |            ^