Under one unified cast syntax C# mixes two conceptually different conversion types:

• Conversions that doesn't change representation: i.e. reference conversions
• Conversions that changes representation: these operations convert source data to another object (like in your case)

F# behavior is different, it separates these operations and use different syntax .
You need to invoke conversion operator explicitly:

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let p = Point(1,2)
// explicit call
let pf = Point.op_Implicit p

// IMO more convinient way
let pointF = Point.op_Implicit
let pf2 = pointF p