Infinite loop on expanding cycle for struct types

```fsharp
[<Struct>]
type MyStruct<'T> =

    val field : YourStruct<MyStruct<MyStruct<'T>>>

and [<Struct>] YourStruct<'T> =

    val field : 'T
```

If you define this in F#, it will cause an infinite loop in the compiler and you will have to kill your process for it to stop.

We expect to receive an error when defining this type.