auto casting Float to Double

gistfile1.swift

extension Float {
    func __conversion() -> Double { return Double(self) }
}

let two = 2.0
let n1 = 1 / 2.0            // Ok
let n2 = Float(1) / 2.0     // Ok
let n3 = Double(1) / 2.0    // Ok
let n4 = CGFloat(1) / 2.0   // Ok
let n5 = 1 / two            // Ok
let n6 = Float(1) / two     // Error
let n7 = Double(1) / two    // Ok
let n8 = CGFloat(1) / two   // Error for 32-bit system.