extern crate proc_macro;
use proc_macro::TokenStream;
use quote::{quote, ToTokens};
use syn::{self, Attribute, Data, Fields};
#[proc_macro_derive(Typemap, attributes(typemap_mut))]
pub fn typemap_macro_derive(input: TokenStream) -> TokenStream {
let ast = syn::parse(input).unwrap();
impl_typemap_macro(&ast)
}
fn impl_typemap_macro(ast: &syn::DeriveInput) -> TokenStream {
let struct_data = if let Data::Struct(s) = &ast.data {
s
} else {
panic!("Typemap only applies to tuple struct, but used on a non-struct!")
};
let tuple_fields = if let Fields::Unnamed(f) = &struct_data.fields {
f
} else {
panic!("Typemap only applies to tuple struct, but used on a non-tuple struct!")
};
let all_mut = has_mut_attr(&ast.attrs);
let types: Vec<_> = tuple_fields
.unnamed
.iter()
.map(|e| e.ty.to_token_stream())
.collect();
let indices: Vec<_> = (0..types.len()).map(syn::Index::from).collect();
let name = &ast.ident;
let generics = &ast.generics;
let gen = quote! {
#(impl #generics Get<#types> for #name #generics {
fn get(&self) -> &#types {
&self.#indices
}
})*
};
let gen_mut = if all_mut {
Some(quote! {
#(impl #generics GetMut<#types> for #name #generics {
fn get_mut(&mut self) -> &mut #types {
&mut self.#indices
}
})*
})
} else {
None
};
quote! {
#gen
#gen_mut
}
.into()
}
fn has_mut_attr(attrs: &[Attribute]) -> bool {
attrs.iter().any(|attr| attr.path.is_ident("typemap_mut"))
}