Add tests and fix IsMappedBy

Author: nicolasstucki

library/src/scala/Tuple.scala

@@ -114,7 +114,7 @@ object Tuple {
    *  (F[A1], ..., F[An]), but not `(F[A1], B2, ..., F[An])` where B2 does not
    *  have the shape of `F[A]`.
    */
-  type IsMappedBy[F[_]] = [X <: Tuple] =>> X <:< Map[InverseMap[X, F], F]
+  type IsMappedBy[F[_]] = [X <: Tuple] =>> X =:= Map[InverseMap[X, F], F]
 
   /** Convert an array into a tuple of unknown arity and types */
   def fromArray[T](xs: Array[T]): Tuple = {

tests/neg/tuple-isMappedBy-2.scala

@@ -0,0 +1,5 @@
+import scala.Tuple.IsMappedBy
+
+object Test2 {
+  def test0[F[_], T: IsMappedBy[F]]: Unit = () // error: Type argument T does not conform to upper bound Tuple
+}

tests/neg/tuple-isMappedBy.scala

@@ -0,0 +1,13 @@
+import scala.Tuple.IsMappedBy
+
+object Test1 {
+
+  def test[F[_], T <: Tuple: IsMappedBy[F]]: Unit = ()
+
+  test[List, (List[Int], Char)] // error
+  test[List, (List[Int], Seq[Char])] // error
+  test[Seq, (List[Int], Seq[Char])] // error
+  test[List, Tuple] // error
+  test[List, Nothing] // error
+
+}

tests/pos/tuple-isMappedBy.scala

@@ -0,0 +1,27 @@
+
+import scala.Tuple.IsMappedBy
+
+object Test {
+
+  def test[F[_], T <: Tuple: IsMappedBy[F]]: Unit = ()
+
+  test[[X] =>> X, Unit]
+  test[[X] =>> X, (Int, Long)]
+
+  test[List, Unit]
+  test[List, (List[Int], List[Long])]
+
+  trait A[+X]
+  trait B[-X]
+  trait C[X]
+
+  test[A, Unit]
+  test[A, (A[Int], A[Long])]
+
+  test[B, Unit]
+  test[B, (B[Int], B[Long])]
+
+  test[C, Unit]
+  test[C, (C[Int], C[Long])]
+
+}