Avoid inf recursion in provablyDisjointClasses

Author: dwijnand

tests/pos/i22266.scala

@@ -0,0 +1,22 @@
+sealed trait NonPolygon
+sealed trait Polygon
+
+sealed trait SymmetryAspect
+sealed trait RotationalSymmetry      extends SymmetryAspect
+sealed trait MaybeRotationalSymmetry extends SymmetryAspect
+
+enum Shape:
+  case Circle   extends Shape with NonPolygon with RotationalSymmetry
+  case Triangle extends Shape with Polygon with MaybeRotationalSymmetry
+  case Square   extends Shape with Polygon with RotationalSymmetry
+
+object Shape:
+
+  def hasPolygon(
+    rotationalSyms: Vector[Shape & RotationalSymmetry],
+    maybeSyms: Vector[Shape & MaybeRotationalSymmetry]
+  ): Boolean =
+    val all = rotationalSyms.concat(maybeSyms)
+    all.exists:
+      case _: Polygon => true
+      case _          => false