openpgp: Don't implement Default for Features.

  - The implementation of `Default` for `Features` returned an empty
    feature set.  This is not a reasonable feature set: the MDC flag
    should almost always be set.

  - Remove the `Default` implementation and use `Features::empty` when
    an empty feature set is really required.

3 files changed, 5 insertions, 13 deletions

diff --git a/openpgp/src/packet/signature/subpacket.rs b/openpgp/src/packet/signature/subpacket.rs
index 4049b15c..3055471c 100644
--- a/openpgp/src/packet/signature/subpacket.rs
+++ b/openpgp/src/packet/signature/subpacket.rs
@@ -2699,13 +2699,13 @@ fn accessors() {
     assert_eq!(sig_.reason_for_revocation(),
                Some((ReasonForRevocation::KeyRetired, &b"foobar"[..])));
 
-    let feats = Features::default().set_mdc();
+    let feats = Features::empty().set_mdc();
     sig = sig.set_features(&feats).unwrap();
     let sig_ =
         sig.clone().sign_hash(&mut keypair, hash.clone()).unwrap();
     assert_eq!(sig_.features().unwrap(), feats);
 
-    let feats = Features::default().set_aead();
+    let feats = Features::empty().set_aead();
     sig = sig.set_features(&feats).unwrap();
     let sig_ =
         sig.clone().sign_hash(&mut keypair, hash.clone()).unwrap();
@@ -2981,13 +2981,13 @@ fn subpacket_test_2() {
                            KeyFlags::default().set_certification(true).set_signing(true))
                    }));
 
-        assert_eq!(sig.features().unwrap(), Features::default().set_mdc());
+        assert_eq!(sig.features().unwrap(), Features::empty().set_mdc());
         assert_eq!(sig.subpacket(SubpacketTag::Features),
                    Some(&Subpacket {
                        length: 2.into(),
                        critical: false,
                        value: SubpacketValue::Features(
-                           Features::default().set_mdc())
+                           Features::empty().set_mdc())
                    }));
 
         let keyid = "F004 B9A4 5C58 6126".parse().unwrap();
diff --git a/openpgp/src/types/features.rs b/openpgp/src/types/features.rs
index 22514d09..ca82f797 100644
--- a/openpgp/src/types/features.rs
+++ b/openpgp/src/types/features.rs
@@ -57,14 +57,6 @@ pub struct Features{
     raw: Vec<u8>,
 }
 
-impl Default for Features {
-    fn default() -> Self {
-        Features {
-            raw: Vec::new(),
-        }
-    }
-}
-
 impl fmt::Debug for Features {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         // Print known features first.
diff --git a/openpgp/src/types/mod.rs b/openpgp/src/types/mod.rs
index d98e2464..83e5ed0b 100644
--- a/openpgp/src/types/mod.rs
+++ b/openpgp/src/types/mod.rs
@@ -737,7 +737,7 @@ impl Arbitrary for SymmetricAlgorithm {
 /// use openpgp::types::{Features, HashAlgorithm, AEADAlgorithm, SignatureType};
 ///
 /// # fn main() -> openpgp::Result<()> {
-/// let features = Features::default().set_aead();
+/// let features = Features::empty().set_aead();
 /// let mut builder = SignatureBuilder::new(SignatureType::DirectKey)
 ///     .set_features(&features)?
 ///     .set_preferred_aead_algorithms(vec![