In base-4.11 (bundled with GHC 8.4.1), there is no longer a default implementation for (<>) in terms of Monoid (after Semigroup became a superclass of Monoid), so using (<>) results in a runtime error. This fixes the issue by simply giving an implementation for (<>) that matches mappend.
In
base-4.11
(bundled with GHC 8.4.1), there is no longer a default implementation for(<>)
in terms ofMonoid
(afterSemigroup
became a superclass ofMonoid
), so using(<>)
results in a runtime error. This fixes the issue by simply giving an implementation for(<>)
that matchesmappend
.