Float cast to nil (bug?)

FloatCast.swift

import Foundation
import UIKit

func swiftVersion() -> String {
    #if swift(>=4.2.1)
    return "4.2.1"
    #elseif swift(>=4.2)
    return "4.2"
    #elseif swift(>=4.1)
    return "4.1"
    #elseif swift(>=4.0)
    return "4.0"
    #endif
}

let version = "Swift \(swiftVersion())"

let value: Any? = 2.5

let a: Float? = value as? Float
let f: CGFloat? = value as? CGFloat
let b: Double? = value as? Double
let c: Float? = (value as? NSNumber)?.floatValue

Result is nil for a and f.