Tightening up on inferred type signatures

[adam vogt]

] GHC generally obeys this rule
]
] ·         If GHC infers a type f::type, then it’s OK for you to add a type
] signature saying exactly that.

That rule suggests that -XScopedTypeVariables should be on by default,
and that you shouldn't need a forall to bring the type variables into
scope. I imagine that would lead to harder-to-fix breakage than #8883,
but on the other hand type signatures in let/where are pretty rare.

Regards,
Adam