Pattern matching for all sequences

SeqPatterns.fs

open System

[<RequireQualifiedAccess>]
module Seq =
    let inline (|Nil|Cons|) (someSeq: seq<_>) =
        
        let mutable enum = Unchecked.defaultof<IEnumerator<_>>
        let mutable shouldDispose = true
        
        try
            enum <- someSeq.GetEnumerator()
            
            if enum.MoveNext() then
                let head = enum.Current
                shouldDispose <- false
                
                let rest = seq {
                    use localEnum = enum
                    while localEnum.MoveNext() do
                        yield localEnum.Current
                }
                
                Cons(head, rest)
            else
                Nil
        finally
            if shouldDispose && not(isNull enum) then
                (enum :> IDisposable).Dispose()

Please ensure these samples properly work (finally should always execute):

let ex1 = seq {
  try
    throw Exception()
  finally
    printfn "Should always print this"
}

let ex2 = seq {
  try
    return! [||]
  finally 
    printfn "Should always print this"
}