monadtest.fs

#r "nuget:FSharpPlus"

open FSharpPlus

type Transaction<'T> = |Transaction of (unit -> 'T)
with
    static member Return (x: 'T) : Transaction<'T> = Transaction.Transaction (fun () -> x)
    static member (>>=) (x: Transaction<'T>, f: 'T -> Transaction<'U>) : Transaction<'U> = 
        match x with Transaction.Transaction fn -> fn () |> f
   
    //For delayed
    static member TryWith (computation: unit -> Transaction<'T>, catchHandler: exn -> Transaction<'T>) : Transaction<'T> = 
        failwithf ""
    static member TryFinally (source: Transaction<'T>, f: unit -> unit) : Transaction<'T> = 
        failwithf ""   


//Works
let c arg : Transaction<string> = monad.strict {
    return arg
}

//Works
let d = monad.strict {
    let! a = c "A"
    let! b = c "B"
    return a+b
}

//unknown(1,1): error FS0073: internal error: Undefined or unsolved type variable: ^_?124161
let e = monad {
    let! a = c "A"
    let! b = c "B"
    return a+b
}