Why is `Eq v` necessary for the `Semigroup` and `Monoid` for the `MaybeDefault` datatype

I'm wondering why we need as type constraint Eq v for the instances of Semigroup and Monoid. While we will likely eventually need the Eq instance, at the instance level of Semigroup and Monoid, we do not make use of any function that is defined in Eq.

vty/src/Graphics/Vty/Attributes.hs

Lines 154 to 163 in fe501cc

    
           instance Eq v => Semigroup (MaybeDefault v) where 
        
               _        <> v@(SetTo _) = v 
        
               x        <> KeepCurrent = x 
        
               _        <> Default     = Default 
        
           instance Eq v => Monoid ( MaybeDefault v ) where 
        
               mempty = KeepCurrent 
        
           #if !(MIN_VERSION_base(4,11,0)) 
        
               mappend = (<>) 
        
           #endif

It turns out we don't! Those constraints are redundant, probably made so by some recent changes. I removed them in abf7fc4 just now. Thanks for mentioning this!

	instance Eq v => Semigroup (MaybeDefault v) where
	_ <> v@(SetTo _) = v
	x <> KeepCurrent = x
	_ <> Default = Default

	instance Eq v => Monoid ( MaybeDefault v ) where
	mempty = KeepCurrent
	#if !(MIN_VERSION_base(4,11,0))
	mappend = (<>)
	#endif