openpgp: Remove SignatureBuilder::set_signature_expiration_time.

  - `SignatureBuilder::set_signature_expiration_time` takes an
    absolute time and converts it to a duration relative to the
    `Signature Creation Time` subpacket.

  - Since we sometimes set the `Signature Creation Time` subpacket
    lazily, this should probably also be set lazily.

  - But that makes the `SignatureBuilder` more complicated.  And, it
    means that `SignatureBuilder::modify_hashed_area`'s behavior is
    more complicated.

  - Instead of adding complexity, only provide the
    `SignatureBuilder::set_signature_validity_period` method, which is
    what is appears to be needed in practice.

1 files changed, 0 insertions, 23 deletions

diff --git a/openpgp/src/packet/signature/subpacket.rs b/openpgp/src/packet/signature/subpacket.rs
index ea8d2b3a..158202ee 100644
--- a/openpgp/src/packet/signature/subpacket.rs
+++ b/openpgp/src/packet/signature/subpacket.rs
@@ -2459,29 +2459,6 @@ impl signature::SignatureBuilder {
         Ok(self)
     }
 
-    /// Sets the value of the Signature Expiration Time subpacket.
-    ///
-    /// If `None` is given, any expiration subpacket is removed.
-    pub fn set_signature_expiration_time<D>(self, expiration: D)
-        -> Result<Self>
-        where D: Into<time::SystemTime>
-    {
-        let expiration = expiration.into();
-        let vp = if let Some(ct) = self.signature_creation_time() {
-            match expiration.duration_since(ct) {
-                Ok(v) => v,
-                Err(_) => return Err(Error::InvalidArgument(
-                    format!("Expiration time {:?} predates creation time \
-                             {:?}", expiration, ct)).into()),
-            }
-        } else {
-            return Err(Error::MalformedPacket(
-                "No creation time subpacket".into()).into());
-        };
-
-        self.set_signature_validity_period(vp)
-    }
-
     /// Sets the value of the Exportable Certification subpacket,
     /// which contains whether the certification should be exported
     /// (i.e., whether the packet is *not* a local signature).