compatible_with_derive/
lib.rs

1use proc_macro::TokenStream;
2use syn::parse_macro_input;
3
4#[proc_macro_derive(CompatibleWith)]
5pub fn derive(input: TokenStream) -> TokenStream {
6    let input = parse_macro_input!(input as syn::DeriveInput);
7    let name = input.ident;
8    let crate_name = syn::Ident::new("compatible_with", proc_macro2::Span::call_site());
9    quote::quote! {
10        impl<Old> From<#crate_name::Compatible<Old, #name>> for #name
11        where
12            Self: #crate_name::CompatibleWith<Old>,
13        {
14            fn from(value: #crate_name::Compatible<Old, #name>) -> Self {
15                value.into_current()
16            }
17        }
18    }
19    .into()
20}