fix nightly clippy

CHANGELOG.md

@@ -3,7 +3,7 @@
 ## v0.5.0-rc.3 -> v0.5.0
 
 - `PointConvertible` trait is now `unsafe` since the offset is used for raw memory access, where safety can not be guaranteed by the compiler.
-- std::error -> core::error for nightly clippy
+- Fixes clippy on nightly.
 - Fixes a bug when attempting to write larger types than available in the message. This now results in a `ExhaustedSource` error.
 - Adds `repr(C)` to docs where custom conversions are explained to encourage best practices for raw type descriptions.
 

rpcl2/src/lib.rs

@@ -225,8 +225,10 @@ impl core::fmt::Display for MsgConversionError {
     }
 }
 
-impl core::error::Error for MsgConversionError {
-    fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
+#[allow(clippy::std_instead_of_core)] // will be stable soon (https://github.com/rust-lang/rust/issues/103765)
+#[cfg(feature = "std")]
+impl std::error::Error for MsgConversionError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
         None
     }
 }