chore: move derive_more to dev-deps

Cargo.toml

@@ -46,7 +46,6 @@ quick-xml = ["serde?/derive", "serde?/alloc"] # FIXME: quick-xml#473
 serde = { version = "1.0", default-features = false, optional = true }
 schemars = { version = "0.8", default-features = false, optional = true }
 typenum = "1.12.0"
-derive_more = { version = "0.99.9", default-features = false }
 parity-scale-codec = { version = "3", default-features = false, optional = true }
 static_assertions = "1.1.0"
 itoa = "1.0.1"
@@ -56,7 +55,7 @@ i256 = { version = "=0.1.1", default-features = false, optional = true }
 anyhow = { version = "1.0.38", default-features = false }
 colored = "2.0.0"
 criterion = "0.5"
-derive_more = "0.99.9"
+derive_more = { version = "1.0.0", features = ["full"] }
 trybuild = "1.0.85"
 serde_json = "1"
 proptest = "1.0.0"

src/errors.rs

@@ -1,10 +1,11 @@
 use core::fmt::{Display, Formatter, Result};
 
+// TODO: once MSRV becomes 1.81, use `core::error::Error` instead.
+// Also, enable doctests in CI checks even for no-std.
 #[cfg(feature = "std")]
-use derive_more::Error;
+use std::error::Error;
 
 /// Represents errors during arithmetic operations.
-#[cfg_attr(feature = "std", derive(Error))]
 #[derive(Clone, Debug, PartialEq, Eq)]
 #[non_exhaustive]
 pub enum ArithmeticError {
@@ -34,8 +35,10 @@ impl Display for ArithmeticError {
     }
 }
 
+#[cfg(feature = "std")]
+impl Error for ArithmeticError {}
+
 /// Represents errors during conversions.
-#[cfg_attr(feature = "std", derive(Error))]
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct ConvertError {
     reason: &'static str,
@@ -57,3 +60,6 @@ impl Display for ConvertError {
         f.write_str(self.as_str())
     }
 }
+
+#[cfg(feature = "std")]
+impl Error for ConvertError {}