Polymorphic functions variance not working as expected

[guyde2011]

minimized code

val aiPoly: [T] => Any => Int = [T] => (a: Any) => 5
val iiPoly: [T] => Int => Int = aiPoly // <-- this part fails

Does not compile, producing the error:
Found: PolyFunction{apply: [T](x$1: Any): Int}(aiPoly)
Required: PolyFunction{apply: [T](x$1: Int): Int}

expectation

Expected the polymorhpic case to behave the same way as normal functions do:

val ai: Any => Int = (a: Any) => 5
val ii: Int => Int = ai // <-- compiles and works with no errors

[smarter]

Same root cause as #6357 since dependent and polymorphic function types share a similar encoding, closing this one as a duplicate since I'll either manage to fix both at the same time or none (details of my current plan here: http://guillaume.martres.me/talks/dotty-funs-scala19/)