build: Use trait Error from core (#1179)

Since Rust 1.81, the `trait Error` is available in core. Therefore `std` is no longer needed for error types

Author: caspermeijn

benchmarks/benches/dataset.rs

@@ -1,6 +1,6 @@
+use core::error::Error;
 use criterion::{criterion_group, criterion_main, Criterion};
 use prost::Message;
-use std::error::Error;
 
 pub mod benchmarks {
     include!(concat!(env!("OUT_DIR"), "/benchmarks.rs"));

prost-types/src/duration.rs

@@ -164,8 +164,7 @@ impl fmt::Display for DurationError {
     }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for DurationError {}
+impl core::error::Error for DurationError {}
 
 impl FromStr for Duration {
     type Err = DurationError;

prost-types/src/timestamp.rs

@@ -185,8 +185,7 @@ impl fmt::Display for TimestampError {
     }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for TimestampError {}
+impl core::error::Error for TimestampError {}
 
 #[cfg(feature = "std")]
 impl TryFrom<Timestamp> for std::time::SystemTime {

prost/src/error.rs

@@ -145,8 +145,7 @@ impl fmt::Display for DecodeErrorKind {
     }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for DecodeError {}
+impl core::error::Error for DecodeError {}
 
 #[cfg(feature = "std")]
 impl From<DecodeError> for std::io::Error {
@@ -196,8 +195,7 @@ impl fmt::Display for EncodeError {
     }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for EncodeError {}
+impl core::error::Error for EncodeError {}
 
 #[cfg(feature = "std")]
 impl From<EncodeError> for std::io::Error {
@@ -220,8 +218,7 @@ impl fmt::Display for UnknownEnumValue {
     }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for UnknownEnumValue {}
+impl core::error::Error for UnknownEnumValue {}
 
 #[cfg(test)]
 mod test {