// let inline foreach f (o:^T when ^T :(member Item : int)) =
let inline foreach f o =
  for i in 0 .. (^T:(member get_Length:int)o) do
    let x = (^T:(member get_Item:int->int->unit)(o,i))
  //  x
  // (^T:(member get_Item:'a->unit) o)
  ()

type Hoge =
  member o.Item
    with get(x:int,y:int) = ()
    and set(x:int,y:int) v = ()

open System.Reflection
let t = typeof<Text.StringBuilder>
for mi in t.GetProperties() do
  // if (string mi).Contains("get") then
    printfn "%A" mi