Add regression test for scala#21215 fixed in scala#21226

tests/pos/i21215.scala

@@ -0,0 +1,45 @@
+
+trait FlatMap[F[_]]:
+  def flatMap[A, B](fa: F[A])(f: A => F[B]): F[B] = ???
+  def ifM[B](ifTrue: => F[B], ifFalse: => F[B])(implicit F: FlatMap[F]): F[B] = ???
+trait Monad[F[_]] extends FlatMap[F]
+trait MonadError[F[_], E] extends Monad[F]:
+  def raiseError[A](e: E): F[A]
+trait Temporal[F[_]] extends MonadError[F, Throwable]
+
+trait FlatMapOps[F[_], A]:
+  def flatMap[B](f: A => F[B]): F[B] = ???
+  def map[B](f: A => B): F[B] = ???
+  def ifM[B](ifTrue: => F[B], ifFalse: => F[B])(implicit F: FlatMap[F]): F[B] = ???
+
+implicit def toFlatMapOps[F[_], A](target: F[A])(implicit tc: FlatMap[F]): FlatMapOps[F, A] = ???
+
+abstract class Ref[F[_], A]
+object Ref:
+  final class ApplyBuilders[F[_]]:
+    def of[A](a: A): F[Ref[F, A]] = ???
+  def apply[F[_]]: ApplyBuilders[F] = ???
+
+trait DatabaseMetaData[F[_]]
+class DatabaseMetaDataImpl[F[_]](
+                                  statementClosed: Ref[F, Boolean],
+                                  resultSetClosed: Ref[F, Boolean]
+                                ) extends DatabaseMetaData[F]
+
+trait LdbcConnection[F[_]]:
+  def getMetaData(): F[DatabaseMetaData[F]]
+
+class ConnectionImpl[F[_]: Temporal](using ev: MonadError[F, Throwable])
+  extends LdbcConnection[F]:
+  def isClosed(): F[Boolean] = ???
+  override def getMetaData(): F[DatabaseMetaData[F]] =
+    isClosed().ifM(
+      ev.raiseError(???),
+      (for
+        statementClosed <- Ref[F].of[Boolean](false)
+        resultSetClosed <- Ref[F].of[Boolean](false)
+      yield DatabaseMetaDataImpl[F](
+        statementClosed,
+        resultSetClosed
+      ))
+    )