docs(primitives): fix rustdoc for Signature (#680)

Author: DaniPopes

crates/core/Cargo.toml

@@ -60,3 +60,5 @@ arbitrary = [
 ]
 k256 = ["alloy-primitives/k256"]
 eip712 = ["alloy-sol-types?/eip712-serde", "alloy-dyn-abi?/eip712"]
+
+unstable-doc = ["alloy-primitives/unstable-doc"]

crates/core/src/lib.rs

@@ -12,6 +12,11 @@ pub use alloy_primitives as primitives;
 #[doc(no_inline)]
 pub use primitives::{hex, uint};
 
+#[cfg(feature = "unstable-doc")]
+#[doc(hidden)]
+#[allow(unused_imports)]
+pub use primitives::PrivateSignature as _;
+
 #[cfg(feature = "dyn-abi")]
 #[doc(inline)]
 pub use alloy_dyn_abi as dyn_abi;

crates/primitives/Cargo.toml

@@ -110,6 +110,8 @@ allocative = ["dep:allocative"]
 # Should not be needed most of the time.
 hex-compat = ["hex/hex"]
 
+unstable-doc = []
+
 [[bench]]
 name = "primitives"
 path = "benches/primitives.rs"

crates/primitives/src/lib.rs

@@ -53,6 +53,12 @@ pub use signed::{BigIntConversionError, ParseSignedError, Sign, Signed};
 mod signature;
 pub use signature::{to_eip155_v, Parity, SignatureError};
 
+/// Only available for documentation purposes.
+// Without this visible (not `#[doc(hidden)]`) re-export, `rustdoc` will not generate documentation
+// for the `Signature` type alias below.
+#[cfg(feature = "unstable-doc")]
+pub use signature::Signature as PrivateSignature;
+
 /// An ECDSA Signature, consisting of V, R, and S.
 #[cfg(feature = "k256")]
 pub type Signature = signature::Signature<k256::ecdsa::Signature>;

crates/primitives/src/signature/mod.rs

@@ -5,6 +5,9 @@ mod parity;
 pub use parity::Parity;
 
 mod sig;
+#[cfg(feature = "unstable-doc")]
+pub use sig::Signature;
+#[cfg(not(feature = "unstable-doc"))]
 pub(crate) use sig::Signature;
 
 mod utils;

crates/primitives/src/signature/sig.rs

@@ -101,6 +101,7 @@ impl From<(k256::ecdsa::Signature, k256::ecdsa::RecoveryId)> for Signature<k256:
 
 #[cfg(feature = "rlp")]
 impl crate::Signature {
+    /// Decode an RLP-encoded VRS signature.
     pub fn decode_rlp_vrs(buf: &mut &[u8]) -> Result<Self, alloy_rlp::Error> {
         use alloy_rlp::Decodable;