feat(key): make layout of {Keypair,XOnlyPublicKey,SecretKey} transparent

Author: nymius

src/key/mod.rs

@@ -479,6 +479,7 @@ impl<'de> serde::Deserialize<'de> for PublicKey {
 /// ```
 /// [`bincode`]: https://docs.rs/bincode
 /// [`cbor`]: https://docs.rs/cbor
+#[repr(transparent)]
 #[derive(Copy, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
 pub struct Keypair(ffi::Keypair);
 impl_fast_comparisons!(Keypair);
@@ -818,6 +819,7 @@ impl CPtr for Keypair {
 /// ```
 /// [`bincode`]: https://docs.rs/bincode
 /// [`cbor`]: https://docs.rs/cbor
+#[repr(transparent)]
 #[derive(Copy, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
 pub struct XOnlyPublicKey(ffi::XOnlyPublicKey);
 impl_fast_comparisons!(XOnlyPublicKey);

src/key/secret.rs

@@ -48,6 +48,7 @@ mod encapsulate {
     /// [`bincode`]: https://docs.rs/bincode
     /// [`cbor`]: https://docs.rs/cbor
     /// [cryptographically secure pseudorandom number generator]: https://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator
+    #[repr(transparent)]
     #[derive(Copy, Clone)]
     pub struct SecretKey([u8; SECRET_KEY_SIZE]);
     // FIXME these two macro call should be moved outside of the encapsulate module