According to the .NET CLR spec, you're not allowed to have a tailcall within a protected ("try") block or it's handler. On the other hand, tail-calls can be op

According to the .NET CLR spec, you're not allowed to have a tailcall within a protected ("try") block or it's handler. On the other hand, tail-calls can be optimized into a while loop, and the F# compiler does this in some cases (check out the IL it produces), so then you could have a recursive tail-call within a try/finally there, it just wouldn't be using the 'tail.call' / 'tail.callvirt' / 'tail.calli' OpCode.