How does topological sorting of kind variables really work?

[Simon Peyton Jones]

| > It's a bit of a shame that type inference doesn't give you a reliable
| > order, but I suppose if you rely on -XTypeApplications working a
| > certain way, you're taking a risk by NOT using a forall.
| 
| Inference is meant to give you a reliable ordering. If it's not, that's a
| bug!


I thought that inferred foralls are Invisible binders (see Note [TyBinders and VisibilityFlags]); and you can't use visible type application for Invisible binders.  

I thought that was because it's hard to specify the order of inferred type variable, just as Ryan says.

So /is/ inference meant to give a reliable ordering?  If so why?  

Also I don't understand why Ryan needs a reliable ordering.

So you can see I'm a bit confused here

Simon