Merge pull request #132 from jchyb/scala-3-fixes

[Scala 3 migration] Replace empty sealed trait with an opaque type in Scala 3

Author: yanns

.scalafmt.conf

@@ -1,7 +1,13 @@
-version = 3.5.3
+version = 3.5.8
 
 runner.dialect = scala213
 
+fileOverride {
+  "glob:**/src/main/scala-3/**" {
+    runner.dialect = scala3
+  }
+}
+
 maxColumn = 100
 
 // Vertical alignment is pretty, but leads to bigger diffs

src/main/scala/sangria/util/tag.scala renamed to src/main/scala-2/sangria/util/tag.scala

@@ -0,0 +1,13 @@
+package sangria.util
+
+object tag {
+  def apply[U] = new Tagger[U]
+
+  type Tag[U]
+  opaque type Tagged[U] = Tag[U]
+  type @@[+T, U] = (T & Tagged[U]) | Null
+
+  class Tagger[U] {
+    def apply[T](t: T): T @@ U = t.asInstanceOf[T @@ U]
+  }
+}