Test for creative GADT constraint usage

Author: abgruszecki

tests/neg/creative-gadt-constraints.scala

@@ -0,0 +1,66 @@
+object buffer {
+  object EssaInt {
+    def unapply(i: Int): Some[Int] = Some(i)
+  }
+
+  case class Inv[T](t: T)
+
+  enum EQ[A, B] { case Refl[T]() extends EQ[T, T] }
+  enum SUB[A, +B] { case Refl[T]() extends SUB[T, T] } // A <: B
+
+  def test_eq1[A, B](eq: EQ[A, B], a: A, b: B): B =
+    Inv(a) match { case Inv(_: Int) => // a >: Sko(Int)
+      Inv(a) match { case Inv(_: Int) => // a >: Sko(Int) | Sko(Int)
+        eq match { case EQ.Refl() => // a = b
+          val success: A = b
+          val fail: A = 0 // error
+          0 // error
+        }
+      }
+    }
+
+  def test_eq2[A, B](eq: EQ[A, B], a: A, b: B): B =
+    Inv(a) match { case Inv(_: Int) => // a >: Sko(Int)
+      Inv(b) match { case Inv(_: Int) => // b >: Sko(Int)
+        eq match { case EQ.Refl() => // a = b
+          val success: A = b
+          val fail: A = 0 // error
+          0 // error
+        }
+      }
+    }
+
+  def test_sub1[A, B](sub: SUB[A, B], a: A, b: B): B =
+    Inv(b) match { case Inv(_: Int) => // b >: Sko(Int)
+      Inv(b) match { case Inv(_: Int) => // b >: Sko(Int) | Sko(Int)
+        sub match { case SUB.Refl() => // b >: a
+          val success: B = a
+          val fail: A = 0 // error
+          0 // error
+        }
+      }
+    }
+
+  def test_sub2[A, B](sub: SUB[A, B], a: A, b: B): B =
+    Inv(a) match { case Inv(_: Int) => // a >: Sko(Int)
+      Inv(b) match { case Inv(_: Int) => // b >: Sko(Int) | Sko(Int)
+        sub match { case SUB.Refl() => // b >: a
+          val success: B = a
+          val fail: A = 0 // error
+          0 // error
+        }
+      }
+    }
+
+
+  def test_sub_eq[A, B, C](sub: SUB[A|B, C], eqA: EQ[A, 5], eqB: EQ[B, 6]): C =
+    sub match { case SUB.Refl() => // C >: A | B
+      eqA match { case EQ.Refl() => // A = 5
+        eqB match { case EQ.Refl() => // B = 6
+          val fail1: A = 0 // error
+          val fail2: B = 0 // error
+          0 // error
+        }
+      }
+    }
+}