Give it a longer, more annoying name, because you're not supposed to
use it anymore. It's fundamentally broken. I've added FIXME comments
in the places where the result is known to be wrong.
A type variable that represents the type of a closure can only be bound
to a function type, but this fact is not directly encoded in the
constraint system.
Check for the appearance of a non-sensical subtype binding on a closure
type variable in reduceBinding(), and promote the binding to exact as
soon as we detect this, since binding the type will always fail; we want
to fail as quickly as possible, before attempting any more disjunctions.
This is a generally good performance optimization, and it also addresses
a performance regression from "Sema: Filter bindings by considering
conformance constraints".
This also speeds up the expression from rdar://59008707, which also uses
Combine and is slow for similar reasons.
This was wrong for classes. Because it was only used from one place
previously, the bug didn't come up, but I'm adding a new caller in
CSBindings shortly.
Slava Pestov