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