Type inference for closures

Boo should pick up a closure's missing parameter types from its context.

Declaration context:

closure as callable(int) as bool  = { i | i > 3 }

Assignment context:

closure as callable(int) as bool
closure = { i | i > 3}

Event subscribe context:

event MyEvent as callable(int) as void
MyEvent += { i | print i }

Cast context:

closure = { i | i > 3 } as Predicate[of int]

Method invocation context:

list = List[of int]()
list.FindAll({ i | i > 3})

This functionality should be combined together with overload resolution and type inference for generic method invocations. This will make Boo's type inference capabilities on par with C# 3.0.