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#![doc(html_root_url = "http://docs.rs/dyn-any-derive/0.1.0")]
extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro2::Span;
use quote::quote;
use syn::{DeriveInput, GenericParam, Lifetime, LifetimeParam, TypeParamBound, parse_macro_input};
/// Derives an implementation for the [`DynAny`] trait.
///
/// # Note
///
/// Currently only works with `struct` inputs.
///
/// # Example
///
/// ## Struct
///
/// ```
/// # use dyn_any::{DynAny, StaticType};
/// #[derive(DynAny)]
/// pub struct Color<'a, 'b> {
/// r: &'a u8,
/// g: &'b u8,
/// b: &'a u8,
/// }
///
///
/// // Generated Impl
///
/// // impl<'dyn_any> StaticType for Color<'dyn_any, 'dyn_any> {
/// // type Static = Color<'static, 'static>;
/// // }
///
/// ```
#[proc_macro_derive(DynAny, attributes(dyn_any_derive))]
pub fn system_desc_derive(input: TokenStream) -> TokenStream {
let ast = parse_macro_input!(input as DeriveInput);
let struct_name = &ast.ident;
let generics = &ast.generics;
let static_params = replace_lifetimes(generics, "'static");
let dyn_params = replace_lifetimes(generics, "'dyn_any");
let old_params = &generics.params.iter().collect::<Vec<_>>();
quote! {
unsafe impl<'dyn_any, #(#old_params,)*> dyn_any::StaticType for #struct_name <#(#dyn_params,)*> {
type Static = #struct_name <#(#static_params,)*>;
}
}
.into()
}
fn replace_lifetimes(generics: &syn::Generics, replacement: &str) -> Vec<proc_macro2::TokenStream> {
let params = generics
.params
.iter()
.map(|param| {
let param = match param {
GenericParam::Lifetime(_) => GenericParam::Lifetime(LifetimeParam::new(Lifetime::new(replacement, Span::call_site()))),
GenericParam::Type(t) => {
let mut t = t.clone();
t.bounds.iter_mut().for_each(|bond| {
if let TypeParamBound::Lifetime(t) = bond {
*t = Lifetime::new(replacement, Span::call_site())
}
});
GenericParam::Type(t.clone())
}
c => c.clone(),
};
quote! {#param}
})
.collect::<Vec<_>>();
params
}
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