openpgp: Hide the `writer::Stackable` trait.

  - Do not expose the `writer::Stackable` trait in the API.  Instead,
    use a tuple struct to wrap boxed objects of this kind.

  - Add and use `writer::Stack::finalize()` and
    `writer::Stack::finalize_all()` to pop one or all writers from the
    stack.

1 files changed, 2 insertions, 7 deletions

diff --git a/openpgp/examples/sign.rs b/openpgp/examples/sign.rs
index f1b8282d..2e212c78 100644
--- a/openpgp/examples/sign.rs
+++ b/openpgp/examples/sign.rs
@@ -45,11 +45,6 @@ fn main() {
         .expect("Failed to sign data");
 
     // Teardown the stack to ensure all the data is written.
-    let signer = literal.into_inner()
-        .expect("Failed to write data")
-        .unwrap();
-
-    let _ = signer.into_inner()
-        .expect("Failed to write data")
-        .unwrap();
+    literal.finalize_all()
+        .expect("Failed to write data");
 }