Speed-up compilation of NifTuple and NifRecord

Author: evnu

rustler_codegen/src/record.rs

@@ -62,22 +62,13 @@ fn gen_decoder(ctx: &Context, fields: &[&Field], atoms_module_name: &Ident) -> T
             } else {
                 index.to_string()
             };
-            let error_message = format!(
-                "Could not decode field {} on Record {}",
-                pos_in_struct,
-                struct_name.to_string()
-            );
             let actual_index = index + 1;
-            let decoder = quote! {
-                match ::rustler::Decoder::decode(terms[#actual_index]) {
-                    Err(_) => return Err(::rustler::Error::RaiseTerm(Box::new(#error_message))),
-                    Ok(value) => value
-                }
-            };
 
             match ident {
-                None => quote! { #decoder },
-                Some(ident) => quote! { #ident: #decoder },
+                None => quote! { try_decode_index(&terms, #pos_in_struct, #actual_index)? },
+                Some(ident) => {
+                    quote! { #ident: try_decode_index(&terms, #pos_in_struct, #actual_index)? }
+                }
             }
         })
         .collect();
@@ -116,6 +107,17 @@ fn gen_decoder(ctx: &Context, fields: &[&Field], atoms_module_name: &Ident) -> T
                     return Err(::rustler::Error::Atom("invalid_record"));
                 }
 
+                fn try_decode_index<'a, T>(terms: &[::rustler::Term<'a>], pos_in_struct: &str, index: usize) -> Result<T, rustler::Error>
+                    where
+                        T: rustler::Decoder<'a>,
+                {
+                    match ::rustler::Decoder::decode(terms[index]) {
+                        Err(_) => Err(::rustler::Error::RaiseTerm(Box::new(
+                                    format!("Could not decode field {} on Record {}", pos_in_struct, #struct_name_str)))),
+                        Ok(value) => Ok(value)
+                    }
+                }
+
                 Ok(
                     #construct
                 )

rustler_codegen/src/tuple.rs

@@ -35,6 +35,7 @@ pub fn transcoder_decorator(ast: &syn::DeriveInput) -> TokenStream {
 fn gen_decoder(ctx: &Context, fields: &[&Field]) -> TokenStream {
     let struct_type = &ctx.ident_with_lifetime;
     let struct_name = ctx.ident;
+    let struct_name_str = struct_name.to_string();
 
     // Make a decoder for each of the fields in the struct.
     let field_defs: Vec<TokenStream> = fields
@@ -47,22 +48,10 @@ fn gen_decoder(ctx: &Context, fields: &[&Field]) -> TokenStream {
             } else {
                 index.to_string()
             };
-            let error_message = format!(
-                "Could not decode field {} on {}",
-                pos_in_struct,
-                struct_name.to_string()
-            );
-
-            let decoder = quote! {
-                match ::rustler::Decoder::decode(terms[#index]) {
-                    Err(_) => return Err(::rustler::Error::RaiseTerm(Box::new(#error_message))),
-                    Ok(value) => value
-                }
-            };
 
             match ident {
-                None => quote! { #decoder },
-                Some(ident) => quote! { #ident: #decoder },
+                None => quote! { try_decode_index(&terms, #pos_in_struct, #index)? },
+                Some(ident) => quote! { #ident: try_decode_index(&terms, #pos_in_struct, #index)? },
             }
         })
         .collect();
@@ -86,6 +75,17 @@ fn gen_decoder(ctx: &Context, fields: &[&Field]) -> TokenStream {
                 if terms.len() != #field_num {
                     return Err(::rustler::Error::BadArg);
                 }
+
+                fn try_decode_index<'a, T>(terms: &[::rustler::Term<'a>], pos_in_struct: &str, index: usize) -> Result<T, rustler::Error>
+                    where
+                        T: rustler::Decoder<'a>,
+                {
+                    match ::rustler::Decoder::decode(terms[index]) {
+                        Err(_) => Err(::rustler::Error::RaiseTerm(Box::new(
+                                    format!("Could not decode field {} on {}", pos_in_struct, #struct_name_str)))),
+                        Ok(value) => Ok(value)
+                    }
+                }
                 Ok(
                     #construct
                 )