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Description
Compiler version
Following the fix to issue 16408 I tried to use
Scala 3.3.2-RC1-bin-20230623-171849f-NIGHTLY
in the scala3 version of banana-rdf.
Minimized code
I adapted the longer code from 16408 in the unreachableCase branch RDF.scala and was able to duplicate the warning.
The difference as seen in this commit is just the addition of
- a
BNodetype - a
type Subject[R <: RDF] = URI[R] | BNode[R] - a
given subjToURITT: TypeTest[RDF.Subject[R], RDF.URI[R]]
(the implementations are in terms of traits rather than a class, but that makes no difference anymore).
import scala.util.Try
import scala.reflect.TypeTest
trait RDF:
rdf =>
type R = rdf.type
type Node <: Matchable
type URI <: Node
type BNode <: Node
given rops: ROps[R]
end RDF
object RDF:
type Node[R <: RDF] = R match
case GetNode[n] => Matchable //n & rNode[R]
type URI[R <: RDF] <: Node[R] = R match
case GetURI[u] => u & Node[R]
type BNode[R <: RDF] <: Node[R] = R match
case GetBNode[b] => b & Node[R]
type Subject[R <: RDF] = URI[R] | BNode[R]
private type GetNode[N] = RDF { type Node = N }
private type GetURI[U] = RDF { type URI = U }
private type GetBNode[B] = RDF { type BNode = B }
end RDF
trait ROps[R <: RDF]:
def mkUri(str: String): Try[RDF.URI[R]]
def auth(uri: RDF.URI[R]): Try[String]
given subjToURITT: TypeTest[RDF.Subject[R], RDF.URI[R]]
object TraitTypes:
trait Node:
def value: String
trait Uri extends Node
trait BNode extends Node
def mkUri(u: String): Uri =
new Uri { def value = u }
object TraitRDF extends RDF:
import TraitTypes as tz
override opaque type Node <: Matchable = tz.Node
override opaque type URI <: Node = tz.Uri
given rops: ROps[R] with
override def mkUri(str: String): Try[RDF.URI[R]] = Try(tz.mkUri(str))
override def auth(uri: RDF.URI[R]): Try[String] =
Try(java.net.URI.create(uri.value).getAuthority())
given subjToURITT: TypeTest[RDF.Subject[R], RDF.URI[R]] with
override def unapply(s: RDF.Subject[R]): Option[s.type & URI] =
s match
case x: (s.type & RDF.URI[R]) => Some(x)
case _ => None
end TraitRDF
class Test[R <: RDF](using rops: ROps[R]):
import rops.given
lazy val uriT: Try[RDF.URI[R]] = rops.mkUri("https://bblfish.net/#i")
lazy val x: String = "uri authority=" + uriT.map(u => rops.auth(u))
@main def run =
val test = Test[TraitRDF.type]
println(test.x)Output
$ scala-cli compile -j 17 -S 3.nightly scala
Compiling project (Scala 3.3.2-RC1-bin-20230623-171849f-NIGHTLY, JVM)
[warn] ./scala/RDF.scala:62:17
[warn] Unreachable case except for null (if this is intentional, consider writing case null => instead).
[warn] case _ => None
[warn] ^
Compiled project (Scala 3.3.2-RC1-bin-20230623-171849f-NIGHTLY, JVM)Expectation
There should be no warning on unreachable case there as clearly the BNode case is possible.