65 lines
2.0 KiB
Rust
65 lines
2.0 KiB
Rust
use proc_macro::TokenStream;
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use quote::quote;
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use syn::{parse_macro_input, parse_quote, DeriveInput};
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pub fn derive_render_once(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 mut trait_generics = ast.generics.clone();
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let view_type = if let Some(view_type) = specified_view_type(&ast) {
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quote! { #view_type }
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} else {
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if let Some(first_type_param) = ast.generics.params.iter().find_map(|param| {
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if let syn::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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quote! { #first_type_param }
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} else {
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trait_generics.params.push(parse_quote! { V: 'static });
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quote! { V }
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}
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};
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let (impl_generics, _, where_clause) = trait_generics.split_for_impl();
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let (_, type_generics, _) = ast.generics.split_for_impl();
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let gen = quote! {
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impl #impl_generics gpui::RenderOnce<#view_type> for #type_name #type_generics
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#where_clause
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{
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type Element = gpui::CompositeElement<#view_type, Self>;
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fn element_id(&self) -> Option<ElementId> {
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None
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}
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fn render_once(self) -> Self::Element {
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gpui::CompositeElement::new(self)
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}
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}
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};
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gen.into()
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}
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fn specified_view_type(ast: &DeriveInput) -> Option<proc_macro2::Ident> {
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ast.attrs.iter().find_map(|attr| {
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if attr.path.is_ident("view") {
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if let Ok(syn::Meta::NameValue(meta_name_value)) = attr.parse_meta() {
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if let syn::Lit::Str(lit_str) = meta_name_value.lit {
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return Some(
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lit_str
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.parse::<syn::Ident>()
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.expect("Failed to parse view_type"),
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);
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}
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}
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}
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None
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})
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}
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