F# Shadowing

The following code produce 48 and 64.

[<EntryPoint>]
let main argv = 
    let x = 64
    if x = 64 then
        let x = x-16
        printfn "%d" x
    printfn "%d" x
    System.Threading.Thread.Sleep 2000 

The disassembled result shows

    let x = 64

00000041  mov         dword ptr [rsp+20h],40h 

    if x = 64 then

00000049  cmp         dword ptr [rsp+20h],40h 

0000004e  jne         0000000000000052 

00000050  jmp         0000000000000057 

00000052  jmp         00000000000000E0 

        let x = x-16

00000057  mov         eax,dword ptr [rsp+20h] 

0000005b  add         eax,0FFFFFFF0h 

0000005e  mov         dword ptr [rsp+24h],eax

Two x in

let x = x-16

are stored in different memory locations.

That is the reason why printfn produce two different results.