Cannot implement distinct seq with setLen

[endragor]

Sample:

type MySeq = distinct seq[int]

proc setLen(s: var MySeq, newLen: Natural) {.borrow.}

var mySeq = MySeq(newSeq[int]())
mySeq.setLen(10)

Error after codegen:

error: request for member 'Sup' in something not a structure or union
  (&myseq_97061_3173352949) = (TY97041*) setLengthSeq(&((&myseq_97061_3173352949))->Sup, sizeof(NI), ((NI) 10));
                                                                                  ^

Nim d6ab21e

[krux02]

as far as I know distinct is something that you should not use at the moment, better use an object with a single member. This does of course not make this less of a bug.

[Araq]

That's not true, distinct is used everywhere and the above is just a bug.

[krux02]

Ok, but I still have a rough memory about a conversation, that involved not using distinct in favor of object.