openpgp: Change packet bodies to be tristate.

  - Packet bodies can now be either unprocessed (e.g. compressed,
    encrypted), processed (e.g. uncompressed, decrypted), or
    structured (e.g. parsed into packets).

  - Make the container types deref to Container, and container deref
    to packet bodies.

  - This cleanly avoids the confusion when serializing containers: We
    can serialize compressed data packets with either body, but we can
    only serialize encryption containers with unprocessed bodies.

  - Fixes #187.

1 files changed, 6 insertions, 4 deletions

diff --git a/openpgp/src/parse/packet_pile_parser.rs b/openpgp/src/parse/packet_pile_parser.rs
index 83fff632..f8c90543 100644
--- a/openpgp/src/parse/packet_pile_parser.rs
+++ b/openpgp/src/parse/packet_pile_parser.rs
@@ -131,9 +131,11 @@ impl<'a> PacketPileParser<'a> {
         for i in 0..position {
             // The most recent child.
             let tmp = container;
-            let packets_len = tmp.children_ref().len();
-            let p = &mut tmp.children_mut()[packets_len - 1];
-            if p.children().next().is_none() {
+            let packets_len = tmp.children_ref().expect("is a container").len();
+            let p = &mut tmp.children_mut()
+                .expect("is a container")
+                [packets_len - 1];
+            if p.children().expect("is a container").next().is_none() {
                 assert!(i == position - 1,
                         "Internal inconsistency while building message.");
             }
@@ -141,7 +143,7 @@ impl<'a> PacketPileParser<'a> {
             container = p.container_mut().unwrap();
         }
 
-        container.children_mut().push(packet);
+        container.children_mut().unwrap().push(packet);
     }
 
     /// Finishes parsing the current packet and starts parsing the