OptionalChaining.swift

let a: Double? = 1.0
let b: Double? = 2.0
let c: Double? = 3.0
let d: Double? = 4.0
let e: Double? = 5.0
let f: Double? = 6.0
let g: Double? = 7.0

extension Optional {
    func `or`(_ value : Wrapped?) -> Optional {
        return self ?? value
    }
    func `or`(_ value: Wrapped) -> Wrapped {
        return self ?? value
    }
}
//let result = a ?? b ?? c ?? d ?? e ?? f ?? g ?? 1.0       // <---  This will fail to compile
let result = a.or(b).or(c).or(d).or(e).or(f).or(g).or(1.0)  // <--- This will not
print(result)

Basically the problem is the type checker constrain solver.