internal error when compiling interface implementation lacking an overloaded method implementation #4967

open System
open System.IO
type IFoo =
  abstract member Foo : t:Type * r:TextReader -> obj
  abstract member Foo<'t> : TextReader -> 't


type Foo() =
  interface IFoo with
    member x.Foo(t, reader) = obj()
    //member x.Foo<'t>(reader) = obj() :?> 't

when I try to compile this, I get an internal error:

error FS0193: internal error: Method 'Foo' in type 'Foo' from assembly 'FSI-ASSEMBLY, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' does not have an implementation.

Instead, I'd expect the compiler to give me:

error FS0366: No implementation was given for 'abstract member IFoo.Foo : TextReader -> 't'. Note that all interface members must be implemented and listed under an appropriate 'interface' declaration, e.g. 'interface ... with member ...'.