fix documentation and misc stuff (#91)

- ran `cargo clippy`, apply all fixes
- ran `cargo fmt`

HandshakeState:
- fix documentation of `write_message`
- move updating of `self.my_turn` from {_(*) -> \1}_message

src/error.rs

@@ -5,6 +5,7 @@ use std::fmt;
 /// All errors in snow will include an `ErrorKind`.
 #[allow(missing_docs)]
 #[derive(Debug)]
+#[non_exhaustive]
 pub enum Error {
     /// The noise pattern failed to parse.
     Pattern(PatternProblem),
@@ -30,12 +31,6 @@ pub enum Error {
     /// Key-encapsulation failed
     #[cfg(feature = "hfs")]
     Kem,
-
-    /// This enum may grow additional variants, so this makes sure clients
-    /// don't count on exhaustive matching. (Otherwise, adding a new variant
-    /// could break existing code.)
-    #[doc(hidden)]
-    __Nonexhaustive,
 }
 
 /// The various stages of initialization used to help identify
@@ -130,7 +125,6 @@ impl fmt::Display for Error {
             Error::Decrypt => write!(f, "decrypt error"),
             #[cfg(feature = "hfs")]
             Error::Kem => write!(f, "kem error"),
-            Error::__Nonexhaustive => write!(f, "Nonexhaustive"),
         }
     }
 }

src/handshakestate.rs

@@ -195,20 +195,20 @@ impl HandshakeState {
     }
 
     /// Construct a message from `payload` (and pending handshake tokens if in handshake state),
-    /// and writes it to the `output` buffer.
+    /// and writes it to the `message` buffer.
     ///
     /// Returns the size of the written payload.
     ///
     /// # Errors
     ///
     /// Will result in `Error::Input` if the size of the output exceeds the max message
     /// length in the Noise Protocol (65535 bytes).
-    #[must_use]
-    pub fn write_message(&mut self, message: &[u8], payload: &mut [u8]) -> Result<usize, Error> {
+    pub fn write_message(&mut self, payload: &[u8], message: &mut [u8]) -> Result<usize, Error> {
         let checkpoint = self.symmetricstate.checkpoint();
-        match self._write_message(message, payload) {
+        match self._write_message(payload, message) {
             Ok(res) => {
                 self.pattern_position += 1;
+                self.my_turn = false;
                 Ok(res)
             },
             Err(err) => {
@@ -317,7 +317,6 @@ impl HandshakeState {
         if self.pattern_position == (self.message_patterns.len() - 1) {
             self.symmetricstate.split(&mut self.cipherstates.0, &mut self.cipherstates.1);
         }
-        self.my_turn = false;
         Ok(byte_index)
     }
 
@@ -338,6 +337,7 @@ impl HandshakeState {
         match self._read_message(message, payload) {
             Ok(res) => {
                 self.pattern_position += 1;
+                self.my_turn = true;
                 Ok(res)
             },
             Err(err) => {
@@ -447,7 +447,6 @@ impl HandshakeState {
         }
 
         self.symmetricstate.decrypt_and_mix_hash(ptr, payload).map_err(|_| Error::Decrypt)?;
-        self.my_turn = true;
         if last {
             self.symmetricstate.split(&mut self.cipherstates.0, &mut self.cipherstates.1);
         }
@@ -463,7 +462,6 @@ impl HandshakeState {
     /// # Errors
     ///
     /// Will result in `Error::Input` if the PSK is not the right length or the location is out of bounds.
-    #[must_use]
     pub fn set_psk(&mut self, location: usize, key: &[u8]) -> Result<(), Error> {
         if key.len() != PSKLEN || self.psks.len() <= location {
             bail!(Error::Input);
@@ -516,10 +514,7 @@ impl HandshakeState {
     pub fn dangerously_get_raw_split(&mut self) -> ([u8; CIPHERKEYLEN], [u8; CIPHERKEYLEN]) {
         let mut output = ([0u8; MAXHASHLEN], [0u8; MAXHASHLEN]);
         self.symmetricstate.split_raw(&mut output.0, &mut output.1);
-        (
-            output.0[..CIPHERKEYLEN].try_into().unwrap(),
-            output.1[..CIPHERKEYLEN].try_into().unwrap()
-        )
+        (output.0[..CIPHERKEYLEN].try_into().unwrap(), output.1[..CIPHERKEYLEN].try_into().unwrap())
     }
 
     /// Convert this `HandshakeState` into a `TransportState` with an internally stored nonce.

src/resolvers/default.rs

@@ -1,4 +1,3 @@
-use aes_gcm;
 use blake2::{Blake2b, Blake2s};
 #[cfg(feature = "xchachapoly")]
 use chacha20poly1305::XChaCha20Poly1305;
@@ -211,7 +210,7 @@ impl Cipher for CipherAesGcm {
             &mut out[..message_len],
             ciphertext[message_len..].into(),
         )
-        .and_then(|_| Ok(message_len))
+        .map(|_| message_len)
         .map_err(|_| ())
     }
 }
@@ -524,12 +523,9 @@ impl Kem for Kyber1024 {
 
 #[cfg(test)]
 mod tests {
-
-    use hex;
-
     use self::hex::FromHex;
     use super::*;
-    use crate::types::*;
+    use hex;
 
     #[test]
     fn test_sha256() {

src/types.rs

@@ -30,7 +30,6 @@ pub trait Dh: Send + Sync {
     fn privkey(&self) -> &[u8];
 
     /// Calculate a Diffie-Hellman exchange.
-    #[must_use]
     fn dh(&self, pubkey: &[u8], out: &mut [u8]) -> Result<(), ()>;
 }
 
@@ -45,7 +44,6 @@ pub trait Cipher: Send + Sync {
     /// Encrypt (with associated data) a given plaintext.
     fn encrypt(&self, nonce: u64, authtext: &[u8], plaintext: &[u8], out: &mut [u8]) -> usize;
 
-    #[must_use]
     /// Decrypt (with associated data) a given ciphertext.
     fn decrypt(
         &self,