let mutable beef = 1

let returning_span (x: byref<int>) = Span.Empty

let returning_ref (x: byref<int>) = &x

let returning_ref2 (x: byref<int>) (y: byref<int>) = &x

let should_not_work1 () =
    let mutable x = 1
    &x

let should_not_work2 () =
    let mutable x = 1
    let mutable x = (let mutable y = &x in &y)

    let y = &returning_ref &x
    &y

let should_not_work3 () =
    let mutable x = 1
    let mutable x =
        match &x with
        | x -> &x

    let y = &returning_ref &x
    &y

let should_not_work4 () =
    let mutable x = 1
    let mutable y = &x
    y <- 1
    &y

let should_not_work5 () =
    let x = 1
    let y = &x
    &y

let should_not_work6 () =
    let mutable x = 1
    &returning_ref &x

let should_not_work7 () =
    let mutable x = 1
    &returning_ref2 &beef &x

let should_not_work8 () =
    let mutable x = 1
    let y = &returning_ref2 &beef &x
    &y

let should_work1 () =
    Span.Empty

let should_work3 () =
    let y = &returning_ref &beef
    &y
    
let should_work2 () =
    let x = Span.Empty
    x

let should_work4 () =
    &returning_ref2 &beef &beef

let should_work5 () =
    let mutable x = 1
    returning_ref2 &x &x

let should_work6 () =
    let mutable x = 1
    returning_span &x

let should_work7 () =
    let mutable x = 1
    let y = returning_span &x
    y

let mutable beef = 1

let returning_span (x: byref<int>) = Span.Empty

let returning_ref (x: byref<int>) = &x

let returning_ref2 (x: byref<int>) (y: byref<int>) = &x

let passing_span_returning_span (x: Span<int>) = Span.Empty

let passing_span_returnin_ref (x: Span<int>) = &x.[0]

let passing_span2 (x: Span<int>) (y: Span<int>) = ()

let passing_byref_of_span_returning_span (x: byref<Span<int>>) = x

let passing_byref_of_span_returning_byref_of_span (x: byref<Span<int>>) = &x

let should_not_work () =
    let test = ReadOnlySpan.Empty
    let f = fun () -> test
    ()

let should_not_work1 () =
    let mutable x = 1
    &x

let should_not_work2 () =
    let mutable x = 1
    let mutable x = (let mutable y = &x in &y)

    let y = &returning_ref &x
    &y

let should_not_work3 () =
    let mutable x = 1
    let mutable x =
        match &x with
        | x -> &x

    let y = &returning_ref &x
    &y

let should_not_work4 () =
    let mutable x = 1
    let mutable y = &x
    y <- 1
    &y

let should_not_work5 () =
    let x = 1
    let y = &x
    &y

let should_not_work6 () =
    let mutable x = 1
    &returning_ref &x

let should_not_work7 () =
    let mutable x = 1
    &returning_ref2 &beef &x

let should_not_work8 () =
    let mutable x = 1
    let y = &returning_ref2 &beef &x
    &y

let should_not_work9 () =
    let mutable s = Span.Empty
    passing_span_returning_span s

let should_not_work10 () =
    let mutable s = Span.Empty
    &passing_span_returnin_ref s

let should_not_work11 () =
    let mutable s = Span.Empty
    &passing_span_returnin_ref (passing_span_returning_span s)

let should_not_work12 () =
    let mutable s = Span.Empty
    passing_byref_of_span_returning_span &s

let should_not_work13 () =
    let mutable s = Span.Empty
    s

let should_not_work14 () =
    let mutable s = Span.Empty
    let mutable x = &s
    passing_byref_of_span_returning_span &x

let should_work1 () =
    Span.Empty

let should_work3 () =
    let y = &returning_ref &beef
    &y
    
let should_work2 () =
    let x = Span.Empty
    x

let should_work4 () =
    &returning_ref2 &beef &beef

let should_work5 () =
    let mutable x = 1
    returning_ref2 &x &x

let should_work6 () =
    let mutable x = 1
    returning_span &x

let should_work7 () =
    let mutable x = 1
    let y = returning_span &x
    y

let should_work8 () =
    let s = Span.Empty
    passing_span_returning_span s

let should_work9 () =
    let mutable s = Span.Empty
    passing_span_returnin_ref s

let should_work10 () =
    let mutable s = Span.Empty
    passing_span_returnin_ref (passing_span_returning_span s)

let should_work11 () =
    let s = Span.Empty
    &passing_span_returnin_ref (passing_span_returning_span s)

let should_work12 () =
    let s = Span.Empty
    passing_byref_of_span_returning_span &s

let should_work13 () =
    let s = Span.Empty
    let mutable x = &s
    passing_byref_of_span_returning_span &x

let should_work14 (s: byref<Span<int>>) =
    passing_byref_of_span_returning_byref_of_span &s

let should_work15 (s: byref<Span<int>>) =
    let x = &s
    let y = &passing_byref_of_span_returning_byref_of_span &x
    &y

type TestDelegate = delegate of byref<Span<int>> -> Span<int>

let should_work16 (s: byref<Span<int>>) =
    let f = TestDelegate(fun _ -> Span.Empty)
    //let mutable s = Span.Empty
    f.Invoke(&s)

type IBeef =

    abstract Test : byref<Span<int>> -> byref<Span<int>>

let should_work17 () =
    { new IBeef with
        member __.Test s = &s
    }