dupit_derive/
lib.rs

1use proc_macro::TokenStream;
2use quote::quote;
3use syn::parse_macro_input;
4use syn::DeriveInput;
5
6#[proc_macro_derive(Duplicate)]
7pub fn impl_duplicate(input: TokenStream) -> TokenStream {
8    // Parse the input tokens into a syntax tree
9    let input = parse_macro_input!(input as DeriveInput);
10
11    let name = input.ident;
12    let generics = &input.generics;
13    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
14
15    // Create the where clause for the Duplicate trait
16    let duplicate_where_clause = {
17        let predicates = where_clause
18            .map(|wc| wc.predicates.iter().collect::<Vec<_>>())
19            .unwrap_or_default();
20
21        if !predicates.is_empty() {
22            quote! { where #(#predicates,)* }
23        } else {
24            quote! {}
25        }
26    };
27
28    // Generate the implementation
29    let expanded = quote! {
30        impl #impl_generics ::dupit::Duplicate for #name #ty_generics #duplicate_where_clause {
31            fn dup(&self) -> Self {
32                use ::dupit::impls::DuplicateImpl;
33                (&&::dupit::impls::Wrapper(self)).duplicate_impl()
34            }
35        }
36    };
37
38    TokenStream::from(expanded)
39}