Fortunately, the type inference algorithm is linear when the nesting depth of polymorphic variables is bounded, as is the case for most applications.
referring to this quote?

I'd assume this is referring to things like bla :: ((forall a. a -> b) -> c) -> d, in which a b c d are all polymorphic, and are nested at different levels

https://3fx.ch/typing-is-hard.html

what does "nested polymorphic variables" mean?

`Fortunately, the type inference algorithm is linear when the nesting depth of polymorphic variables is bounded, as is the case for most applications.`

referring to this quote?

I'd assume this is referring to things like

`bla :: ((forall a. a -> b) -> c) -> d`

, in which a b c d are all polymorphic, and are nested at different levelsI see