feat/refactor(rlp): improve implementations (#182)

* feat/refactor(rlp): improve implementations

* fix: update rlp derive macros and primitives impls

* chore: where clause order

crates/primitives/src/bits/macros.rs

@@ -168,7 +168,7 @@ macro_rules! wrap_fixed_bytes {
 
         $crate::impl_fixed_bytes_traits!($name, $n);
         $crate::impl_getrandom!($name);
-        $crate::impl_rlp!($name);
+        $crate::impl_rlp!($name, $n);
         $crate::impl_serde!($name);
         $crate::impl_arbitrary!($name, $n);
 
@@ -377,10 +377,10 @@ macro_rules! impl_getrandom {
 #[macro_export]
 #[cfg(feature = "rlp")]
 macro_rules! impl_rlp {
-    ($t:ty) => {
+    ($t:ty, $n:literal) => {
         impl $crate::private::alloy_rlp::Decodable for $t {
             #[inline]
-            fn decode(buf: &mut &[u8]) -> Result<Self, $crate::private::alloy_rlp::DecodeError> {
+            fn decode(buf: &mut &[u8]) -> $crate::private::alloy_rlp::Result<Self> {
                 $crate::private::alloy_rlp::Decodable::decode(buf).map(Self)
             }
         }
@@ -396,14 +396,18 @@ macro_rules! impl_rlp {
                 $crate::private::alloy_rlp::Encodable::encode(&self.0, out)
             }
         }
+
+        $crate::private::alloy_rlp::impl_max_encoded_len!($t, {
+            $n + $crate::private::alloy_rlp::length_of_length($n)
+        });
     };
 }
 
 #[doc(hidden)]
 #[macro_export]
 #[cfg(not(feature = "rlp"))]
 macro_rules! impl_rlp {
-    ($t:ty) => {};
+    ($t:ty, $n:literal) => {};
 }
 
 #[doc(hidden)]

crates/primitives/src/bits/rlp.rs

@@ -1,9 +1,9 @@
 use super::FixedBytes;
-use alloy_rlp::{impl_max_encoded_len, length_of_length, Decodable, Encodable};
+use alloy_rlp::{length_of_length, Decodable, Encodable, MaxEncodedLen, MaxEncodedLenAssoc};
 
 impl<const N: usize> Decodable for FixedBytes<N> {
     #[inline]
-    fn decode(buf: &mut &[u8]) -> Result<Self, alloy_rlp::DecodeError> {
+    fn decode(buf: &mut &[u8]) -> alloy_rlp::Result<Self> {
         Decodable::decode(buf).map(Self)
     }
 }
@@ -24,8 +24,12 @@ impl<const N: usize> Encodable for FixedBytes<N> {
 // https://github.com/rust-lang/rust/issues/76560
 macro_rules! fixed_bytes_max_encoded_len {
     ($($sz:literal),+) => {$(
-        impl_max_encoded_len!(FixedBytes<$sz>, $sz + length_of_length($sz));
+        unsafe impl MaxEncodedLen<{ $sz + length_of_length($sz) }> for FixedBytes<$sz> {}
     )+};
 }
 
 fixed_bytes_max_encoded_len!(0, 1, 2, 4, 8, 16, 20, 32, 64, 128, 256, 512, 1024);
+
+unsafe impl<const N: usize> MaxEncodedLenAssoc for FixedBytes<N> {
+    const LEN: usize = N + length_of_length(N);
+}

crates/primitives/src/bytes/rlp.rs

@@ -2,17 +2,20 @@ use super::Bytes;
 use alloy_rlp::{Decodable, Encodable};
 
 impl Encodable for Bytes {
+    #[inline]
     fn length(&self) -> usize {
         self.0.length()
     }
 
+    #[inline]
     fn encode(&self, out: &mut dyn bytes::BufMut) {
         self.0.encode(out)
     }
 }
 
 impl Decodable for Bytes {
-    fn decode(buf: &mut &[u8]) -> Result<Self, alloy_rlp::DecodeError> {
-        Ok(Self(bytes::Bytes::decode(buf)?))
+    #[inline]
+    fn decode(buf: &mut &[u8]) -> Result<Self, alloy_rlp::Error> {
+        bytes::Bytes::decode(buf).map(Self)
     }
 }

crates/rlp-derive/src/de.rs

@@ -1,4 +1,6 @@
-use crate::utils::{attributes_include, field_ident, is_optional, parse_struct, EMPTY_STRING_CODE};
+use crate::utils::{
+    attributes_include, field_ident, is_optional, make_generics, parse_struct, EMPTY_STRING_CODE,
+};
 use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{Error, Result};
@@ -11,92 +13,86 @@ pub(crate) fn impl_decodable(ast: &syn::DeriveInput) -> Result<TokenStream> {
     let supports_trailing_opt = attributes_include(&ast.attrs, "trailing");
 
     let mut encountered_opt_item = false;
-    let mut stmts = Vec::with_capacity(body.fields.len());
+    let mut decode_stmts = Vec::with_capacity(body.fields.len());
     for (i, field) in fields {
         let is_opt = is_optional(field);
         if is_opt {
             if !supports_trailing_opt {
-                return Err(Error::new_spanned(field, "Optional fields are disabled. Add `#[rlp(trailing)]` attribute to the struct in order to enable"));
+                let msg = "optional fields are disabled.\nAdd the `#[rlp(trailing)]` attribute to the struct in order to enable optional fields";
+                return Err(Error::new_spanned(field, msg))
             }
             encountered_opt_item = true;
         } else if encountered_opt_item && !attributes_include(&field.attrs, "default") {
-            return Err(Error::new_spanned(
-                field,
-                "All subsequent fields must be either optional or default.",
-            ))
+            let msg =
+                "all the fields after the first optional field must be either optional or default";
+            return Err(Error::new_spanned(field, msg))
         }
 
-        stmts.push(decodable_field(i, field, is_opt));
+        decode_stmts.push(decodable_field(i, field, is_opt));
     }
 
     let name = &ast.ident;
-    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
-
-    let impl_block = quote! {
-        impl #impl_generics alloy_rlp::Decodable for #name #ty_generics #where_clause {
-            fn decode(mut buf: &mut &[u8]) -> Result<Self, alloy_rlp::DecodeError> {
-                let b = &mut &**buf;
-                let rlp_head = alloy_rlp::Header::decode(b)?;
-
-                if !rlp_head.list {
-                    return Err(alloy_rlp::DecodeError::UnexpectedString);
-                }
-                if alloy_rlp::Buf::remaining(b) < rlp_head.payload_length {
-                    return Err(alloy_rlp::DecodeError::InputTooShort);
-                }
-
-                let started_len = b.len();
-                let this = Self {
-                    #(#stmts)*
-                };
-
-                let consumed = started_len - b.len();
-                if consumed != rlp_head.payload_length {
-                    return Err(alloy_rlp::DecodeError::ListLengthMismatch {
-                        expected: rlp_head.payload_length,
-                        got: consumed,
-                    });
-                }
-
-                *buf = *b;
-
-                Ok(this)
-            }
-        }
-    };
+    let generics = make_generics(&ast.generics, quote!(alloy_rlp::Decodable));
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
 
     Ok(quote! {
         const _: () = {
             extern crate alloy_rlp;
-            #impl_block
+
+            impl #impl_generics alloy_rlp::Decodable for #name #ty_generics #where_clause {
+                #[inline]
+                fn decode(b: &mut &[u8]) -> alloy_rlp::Result<Self> {
+                    let alloy_rlp::Header { list, payload_length } = alloy_rlp::Header::decode(b)?;
+                    if !list {
+                        return Err(alloy_rlp::Error::UnexpectedString);
+                    }
+
+                    let started_len = b.len();
+                    if started_len < payload_length {
+                        return Err(alloy_rlp::DecodeError::InputTooShort);
+                    }
+
+                    let this = Self {
+                        #(#decode_stmts)*
+                    };
+
+                    let consumed = started_len - b.len();
+                    if consumed != payload_length {
+                        return Err(alloy_rlp::Error::ListLengthMismatch {
+                            expected: payload_length,
+                            got: consumed,
+                        });
+                    }
+
+                    Ok(this)
+                }
+            }
         };
     })
 }
 
 pub(crate) fn impl_decodable_wrapper(ast: &syn::DeriveInput) -> Result<TokenStream> {
     let body = parse_struct(ast, "RlpEncodableWrapper")?;
 
-    assert_eq!(
-        body.fields.iter().count(),
-        1,
-        "#[derive(RlpEncodableWrapper)] is only defined for structs with one field."
-    );
+    if body.fields.iter().count() != 1 {
+        let msg = "`RlpEncodableWrapper` is only defined for structs with one field.";
+        return Err(Error::new(ast.ident.span(), msg))
+    }
 
     let name = &ast.ident;
-    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
-
-    let impl_block = quote! {
-        impl #impl_generics alloy_rlp::Decodable for #name #ty_generics #where_clause {
-            fn decode(buf: &mut &[u8]) -> Result<Self, alloy_rlp::DecodeError> {
-                Ok(Self(alloy_rlp::Decodable::decode(buf)?))
-            }
-        }
-    };
+    let generics = make_generics(&ast.generics, quote!(alloy_rlp::Decodable));
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
 
     Ok(quote! {
         const _: () = {
             extern crate alloy_rlp;
-            #impl_block
+
+            impl #impl_generics alloy_rlp::Decodable for #name #ty_generics #where_clause {
+                #[inline]
+                fn decode(buf: &mut &[u8]) -> alloy_rlp::Result<Self> {
+                    alloy_rlp::private::Result::map(alloy_rlp::Decodable::decode(buf), Self)
+                }
+            }
         };
     })
 }
@@ -105,12 +101,12 @@ fn decodable_field(index: usize, field: &syn::Field, is_opt: bool) -> TokenStrea
     let ident = field_ident(index, field);
 
     if attributes_include(&field.attrs, "default") {
-        quote! { #ident: Default::default(), }
+        quote! { #ident: alloy_rlp::private::Default::default(), }
     } else if is_opt {
         quote! {
-            #ident: if started_len - b.len() < rlp_head.payload_length {
-                if b.first().map(|b| *b == #EMPTY_STRING_CODE).unwrap_or_default() {
-                    bytes::Buf::advance(b, 1);
+            #ident: if started_len - b.len() < payload_length {
+                if alloy_rlp::private::Option::map_or(b.first(), false, |b| *b == #EMPTY_STRING_CODE) {
+                    alloy_rlp::Buf::advance(b, 1);
                     None
                 } else {
                     Some(alloy_rlp::Decodable::decode(b)?)