Add regression test for scala#20288 fixed in scala#20527

Close scala#20288

tests/pos/i20288.scala

@@ -0,0 +1,23 @@
+
+trait Decoder[A]
+object Decoder {
+  given Decoder[DataRow] = ???
+  extension [A <: Tuple](d: Decoder[A])
+    def ~[B](fd: Field[B]): Decoder[Tuple.Concat[A, Tuple1[B]]] = ???
+}
+
+trait Field[A]
+object Field:
+  val int: Field[Int] = ???
+  extension [A](self: Field[A])
+    def ~[B](that: Field[B])(using Decoder[DataRow]): Decoder[(A, B)] = ???
+
+trait DataRow
+def simpleQuery[S, A](query: String)(using Decoder[A]): Either[Throwable, A] = ???
+
+@main def Test = {
+  import Decoder.*
+  val fails = simpleQuery("")(using
+    Field.int ~ Field.int ~ Field.int
+  )
+}