Merge pull request #11528 from dotty-staging/fix-t12237

Add test for t12237

Author: liufengyun

tests/patmat/t12237.check

@@ -0,0 +1 @@
+21: Pattern Match Exhaustivity: Root, PathAndQuery./(_, _), PathAndQuery.===(_, _), PathAndQuery.:&(_, PathAndQuery.===(_, _)), PathAndQuery.+?(_, PathAndQuery.===(_, _))

tests/patmat/t12237.scala

@@ -0,0 +1,26 @@
+sealed trait PathAndQuery
+sealed trait Path extends PathAndQuery
+sealed trait Query extends PathAndQuery
+
+object PathAndQuery {
+  case object Root extends Path
+  case class /(prev: Path, value: String) extends Path
+  case class ===(k: String, v: String) extends Query
+  case class :&(prev: Query, next:(===)) extends Query
+  case class +?(path: Path, next:(===)) extends Query
+}
+
+import PathAndQuery._
+
+class Test {
+  val path = /(/(Root, "page"), "1")
+  val q1 = ===("k1", "v1")
+  val q2 = ===("k2", "v2")
+  val pq = :&(+?(path, q1), q2)
+
+  (pq: PathAndQuery) match {
+    case Root / "page" / "1" => println("match 1")
+    case Root / "page" / "1" +? ("k1" === "v1") => println("match 2")
+    case Root / "page" / "1" +? ("k1" === "v1") :& ("k2" === "v2") => println("match 3")
+  }
+}