Strange order dependency of members with cancellable tasks

This code:
```fsharp
namespace Microsoft.VisualStudio.FSharp.Editor

open CancellableTasks

type MyType() = class end

[]
module MyTypeExtensions =

type MyType with

member this.MemberX() =
cancellableTask {
return 42
}

member this.MemberY() =
cancellableTask {
let! result = this.MemberX()
return result
}
```

... compiles just fine:

But rearranging the members produces an error:

The error being something hard stuff about CE:

---

But this shouldn't be, right? Take vanilla `async` for example: