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scalapattern-matchinghttp4s

Unreachable Code warning in http4s route pattern matching

I have this simple Route defined with http4s:

def routes: HttpRoutes[UserTask] =
    HttpRoutes.of[UserTask] {
      case GET -> Root / IntVar(id) =>
        ... // returns a specific user
      case GET -> Root => // this line gives the warning
        Persistence.>.all().foldM( ... // returns all users
      case request@POST -> Root =>
      ....

    }

The Route works as expected.

Is there a way to avoid this warning?

Here is the stacktrace:

[info] Compiling 21 Scala sources to /Users/mpa/dev/Github/pme123/zio-examples/out/entity/compile/dest/classes ...
[warn] /Users/mpa/dev/Github/pme123/zio-examples/entity/src/pme123/zio/examples/api/Api.scala:24:34: unreachable code
[warn]         Persistence.>.all().foldM(_ => NotFound(), Ok(_))
[warn]                                  ^
[warn] one warning found
[info] Done compiling.
Solution

  • There is a bug with Scala 2.13, as @jenshalm told me on Gitter. See scala/bug#11457

    And a fix as mentioned by @rossabaker. See http4s/issues/2933