Add tests from #22645

Author: aherlihy

tests/pos/i22645a.scala

@@ -0,0 +1,44 @@
+import language.experimental.namedTuples
+object ExhibitA:  //  fails
+
+  class SelectableNT[N <: Tuple] extends Selectable:
+    def selectDynamic(name: String) = ???
+    type Names = Tuple.Map[N, [X] =>> X]
+    type Fields = NamedTuple.NamedTuple[Names, (String, Int)]
+
+  val x = new SelectableNT[("name", "age")]
+  x.name  // fails
+
+
+object ExhibitB:  //  works
+
+  class SelectableNT[N <: Tuple] extends Selectable:
+    def selectDynamic(name: String) = ???
+    type Fields = NamedTuple.NamedTuple[N, (String, Int)]
+
+  val x = new SelectableNT[("name", "age")]
+  x.name
+
+
+object ExhibitC:  // works
+
+  class SelectableNT[N <: Tuple] extends Selectable:
+    def selectDynamic(name: String) = ???
+    type Fields = NamedTuple.NamedTuple[N, (String, Int)]
+
+  type N = ("name", "age")
+  val x = new SelectableNT[N]
+  x.name
+
+
+object ExhibitD:  // works
+
+  class SelectableNT[N <: Tuple] extends Selectable:
+    def selectDynamic(name: String) = ???
+    type Fields = NamedTuple.NamedTuple[N, (String, Int)]
+
+  type N = ("name", "age")
+  type Names = Tuple.Map[N, [X] =>> X]
+  val x = new SelectableNT[Names]
+  x.name
+