Add test for #20377 fixed in #20504

Author: EugeneFlesselle

Diff for: tests/pos/i20377.scala

@@ -0,0 +1,23 @@
+import language.experimental.namedTuples
+import NamedTuple.{NamedTuple, AnyNamedTuple}
+
+// Repros for bugs or questions
+class ClassToMap[A]()
+abstract class ClassToFind[Rows <: AnyNamedTuple]:
+  def mapped: NamedTuple.Map[Rows, ClassToMap]
+
+given TDB: ClassToFind[(t1: Int, t2: String)] with
+  override def mapped = (
+    t1 = ClassToMap[Int](),
+    t2 = ClassToMap[String]()
+  )
+
+type TypeAlias = (t1: Int, t2: String)
+class Repro1_Pass(using val testDB: ClassToFind[TypeAlias]) {
+  def query() =
+    testDB.mapped.t1
+}
+class Repro1_Fail(using val testDB: ClassToFind[(t1: Int, t2: String)]) {
+  def query() =
+    testDB.mapped.t1 // fails to compile
+}