forked from mirrors/jj
38 lines
1.3 KiB
Rust
38 lines
1.3 KiB
Rust
mod content_hash;
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extern crate proc_macro;
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use quote::quote;
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use syn::parse_macro_input;
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use syn::DeriveInput;
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/// Derive macro generating an impl of the trait `ContentHash`.
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///
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/// Derives the `ContentHash` trait for a struct by calling `ContentHash::hash`
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/// on each of the struct members in the order that they're declared. All
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/// members of the struct must implement the `ContentHash` trait.
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#[proc_macro_derive(ContentHash)]
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pub fn derive_content_hash(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
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let input = parse_macro_input!(input as DeriveInput);
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// The name of the struct.
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let name = &input.ident;
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// Generate an expression to hash each of the fields in the struct.
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let hash_impl = content_hash::generate_hash_impl(&input.data);
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// Handle structs and enums with generics.
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let generics = content_hash::add_trait_bounds(input.generics);
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let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
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let expanded = quote! {
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#[automatically_derived]
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impl #impl_generics ::jj_lib::content_hash::ContentHash for #name #ty_generics
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#where_clause {
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fn hash(&self, state: &mut impl digest::Update) {
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#hash_impl
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}
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}
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};
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expanded.into()
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}
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