Overload resolution and inline trick

Overload.fsx

type Term<'a>() = class end

type Tuples = Tuples with
    static member inline (?<-) (_ : Tuples, _ : Term<_>, _ : Term<_>) = 0
    static member inline (?<-) (_ : Tuples, (_:Term<_>,_:Term<_>),(_:Term<_>, _:Term<_>)) = 2
    static member inline (?<-) (_ : Tuples, a:bool, b:bool) = 3

let inline call_2 (t:^t,a:^a,b:^a) : int = 
    (t ? (a) <- b ) 
    

let t = call_2 (Tuples,Term<int>(),Term<int>())
let t2 = call_2 (Tuples,(Term<int>(),Term<int>()),(Term<int>(),Term<int>()))
let t3 = call_2 (Tuples, true, false)

let inline call a b : int =
    call_2 (Tuples, a, b)

Incidentally, if you remove the bool overload, again the call is properly generalized.