94 lines
2.7 KiB
Rust
94 lines
2.7 KiB
Rust
use proc_macro::TokenStream;
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use quote::{format_ident, quote};
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use syn::{
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parse_macro_input, parse_quote, DeriveInput, GenericParam, Generics, Ident, Lit, Meta,
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WhereClause,
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};
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pub fn derive_into_element(input: TokenStream) -> TokenStream {
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let ast = parse_macro_input!(input as DeriveInput);
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let type_name = ast.ident;
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let crate_name: String = ast
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.attrs
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.iter()
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.find_map(|attr| {
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if attr.path.is_ident("element_crate") {
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match attr.parse_meta() {
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Ok(Meta::NameValue(nv)) => {
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if let Lit::Str(s) = nv.lit {
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Some(s.value())
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} else {
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None
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}
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}
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_ => None,
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}
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} else {
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None
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}
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})
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.unwrap_or_else(|| String::from("playground"));
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let crate_name = format_ident!("{}", crate_name);
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let placeholder_view_generics: Generics = parse_quote! { <V: 'static> };
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let placeholder_view_type_name: Ident = parse_quote! { V };
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let view_type_name: Ident;
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let impl_generics: syn::ImplGenerics<'_>;
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let type_generics: Option<syn::TypeGenerics<'_>>;
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let where_clause: Option<&'_ WhereClause>;
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match ast.generics.params.iter().find_map(|param| {
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if let GenericParam::Type(type_param) = param {
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Some(type_param.ident.clone())
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} else {
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None
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}
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}) {
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Some(type_name) => {
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view_type_name = type_name;
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let generics = ast.generics.split_for_impl();
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impl_generics = generics.0;
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type_generics = Some(generics.1);
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where_clause = generics.2;
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}
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_ => {
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view_type_name = placeholder_view_type_name;
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let generics = placeholder_view_generics.split_for_impl();
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impl_generics = generics.0;
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type_generics = None;
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where_clause = generics.2;
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}
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}
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impl_into_element(
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&impl_generics,
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&crate_name,
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&view_type_name,
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&type_name,
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&type_generics,
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&where_clause,
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)
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.into()
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}
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pub fn impl_into_element(
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impl_generics: &syn::ImplGenerics<'_>,
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crate_name: &Ident,
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view_type_name: &Ident,
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type_name: &Ident,
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type_generics: &Option<syn::TypeGenerics<'_>>,
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where_clause: &Option<&WhereClause>,
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) -> proc_macro2::TokenStream {
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quote! {
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impl #impl_generics #crate_name::element::IntoElement<#view_type_name> for #type_name #type_generics
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#where_clause
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{
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type Element = Self;
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fn into_element(self) -> Self {
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self
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}
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}
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}
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}
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