Unify named wildcards in different type applications

(motivating post)

I would like to use type application to specialize

Sub :: forall (a :: Constraint) (b :: Constraint). (a => Dict b) -> a :- b
Sub @(Ord _a) @(Eq _a) :: forall {a}. (Ord a => Dict (Eq a)) -> Ord a :- Eq a

and

map :: forall a b. (a -> b) -> [a] -> [b]
map @_a @_a :: forall {a}. (a -> a) -> [a] -> [a]

Is there a fundamental reason why named wildcards are not allowed to unify between type applications within the same expression? Documentation:

These are called named wildcards. All occurrences of the same named wildcard within one type signature will unify to the same type.

I don't know if this is intended.

Trac metadata

Trac field	Value
Version	8.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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