fix: feature-gate symbols to resolve dead-code warning (#3175)

Author: jxs

core/src/identity/error.rs

@@ -82,6 +82,11 @@ impl DecodingError {
         }
     }
 
+    #[cfg(any(
+        all(feature = "rsa", not(target_arch = "wasm32")),
+        feature = "secp256k1",
+        feature = "ecdsa"
+    ))]
     pub(crate) fn encoding_unsupported(key_type: &'static str) -> Self {
         Self {
             msg: format!("encoding {key_type} key to Protobuf is unsupported"),

transports/quic/src/provider.rs

@@ -32,6 +32,7 @@ pub mod async_std;
 pub mod tokio;
 
 /// Size of the buffer for reading data 0x10000.
+#[cfg(any(feature = "async-io", feature = "tokio"))]
 const RECEIVE_BUFFER_SIZE: usize = 65536;
 
 /// Provider for non-blocking receiving and sending on a [`std::net::UdpSocket`]