issue in datatype/module name conflict

[gancherj]

module {:extern "M"} M {
    datatype M = M(x : nat)
}

method Main() {
    var M := M.M(3);
}

The above fails to compile (but succeeds in verifying) with error error CS0426: The nested type `M' does not exist in the type `M.M'

If I get rid of the extern, it compiles successfully.