[Circe] Recursive type derivation doesn't pick up default codecs

[vpavkin]

Reproduction: https://github.com/vpavkin/magnolia/blob/e278256e713ddf3b1aa3365898e930eff168274b/tests/src/main/scala/CirceRecursiveTypeTest.scala

For types of this shape:

case class Recursive(field: Int, recursion: List[Recursive])

Problem here is that we expect the same behaviour as shapeless Lazy provides - the derived codec itself would be visible and used to construct the codec for List using circe std one.

Magnolia doesn't see it and derives coproduct codec for List instead, which doesn't look nice for json API:

  {
   "::":{
      "head":{
         "field":2,
         "recursion":{
            "Nil":"Nil"
         }
      },
      "tl$access$1":{
         "Nil":"Nil"
      }
   }
}

[joroKr21]

Turning on -Xlog-implicits shows (disregarding noise) an access error for magnolia.Deferred. It looks like it should be made public for the sole purpose of typechecking.

[vpavkin]

Actually I found another small problem, related to this particular testcase. Will file another issue.