http4s 路由模式匹配中无法访问的代码警告

Question

我用 http4s:

定义了这个简单的路由

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 =>
      ....

    }

路由按预期运行。

有没有办法避免这个警告？

这是堆栈跟踪：

[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.

Answer 1

Scala 2.13 有一个错误，@jenshalm 在 Gitter 上告诉我。参见 scala/bug#11457

以及@rossabaker 提到的修复。参见 http4s/issues/2933

http4s 路由模式匹配中无法访问的代码警告

Unreachable Code warning in http4s route pattern matching

scala

pattern-matching

http4s