inmem: Copy requires either SenderTo or ReceiverFrom

Signed-off-by: Solomon Hykes <solomon@docker.com>

inmem/copy.go

@@ -1,7 +1,6 @@
 package inmem
 
 import (
-	"io"
 	"fmt"
 )
 
@@ -23,31 +22,6 @@ func Copy(dst Sender, src Receiver) (int, error) {
 	var (
 		n int
 	)
-	for {
-		msg, r, w, err := src.Receive(R|W)
-		if err == io.EOF {
-			break
-		}
-		if r != nil {
-			// FIXME: spawn goroutines to shuttle messages for each
-			// level of nested sender/receiver.
-			r.Close()
-			return n, fmt.Errorf("operation not supported")
-		}
-		if w != nil {
-			// FIXME: spawn goroutines to shuttle messages for each
-			// level of nested sender/receiver.
-			w.Close()
-			return n, fmt.Errorf("operation not supported")
-		}
-		if err != nil {
-			return n, err
-		}
-		if _, _, err := dst.Send(msg, 0); err != nil {
-			return n, err
-		}
-		n++
-	}
-	return n, nil
+	return n, fmt.Errorf("operation not supported")
 }