Function derive

crates/csskit_derives/src/visitable.rs:176–297

(input: DeriveInput)

}

pub fn derive(input: DeriveInput) -> Result<TokenStream> {
	if matches!(input.data, Data::Union(_)) {
		return Err(Error::new(input.ident.span(), "Cannot derive Visitable on a Union"));
	}
	if let Data::Struct(ref s) = input.data
		&& matches!(s.fields, Fields::Unit)
	{
		return Err(Error::new(input.ident.span(), "Cannot derive Visitable on this struct"));
	}

	let style: VisitStyle = VisitStyle::from(input.attrs.as_slice());
	let is_queryable = style.visit_self();
	let ident = &input.ident;
	let (impl_generics, type_generics, _) = input.generics.split_for_impl();

	let (visit_mut, exit_mut) = if style.visit_self() {
		let visit_method = format_ident!("visit_{}", ident.to_string().to_snake_case());
		let exit_method = format_ident!("exit_{}", ident.to_string().to_snake_case());
		(quote! { v.#visit_method(self); }, quote! { v.#exit_method(self); })
	} else {
		(quote! {}, quote! {})
	};

	let (visit_feature, exit_feature) = if has_feature_metadata(&input.attrs) {
		(quote! { v.visit_feature(self); }, quote! { v.exit_feature(self); })
	} else {
		(quote! {}, quote! {})
	};

	let mut s = Structure::try_new(&input)?;
	s.add_bounds(AddBounds::None);

	let mut wc = WhereCollector::new();

	let (body_mut, body) = if style.visit_children() {
		let accept_mut = format_ident!("accept_mut");
		let accept = format_ident!("accept");
		let b_mut = make_body(&s, &accept_mut, &mut wc, false);
		let b = make_body(&s, &accept, &mut wc, true);
		(b_mut, b)
	} else {
		(quote! {}, quote! { <visit_flow::VisitFlow as visit_flow::VisitFlowExt>::DESCEND })
	};

	let accept_body = if is_queryable {
		let node_var = quote! { __node };
		let children_block = if style.visit_self() {
			let visit_method = format_ident!("visit_{}", ident.to_string().to_snake_case());
			let exit_method = format_ident!("exit_{}", ident.to_string().to_snake_case());
			quote! {
				if let visit_flow::VisitAction::Descend = visit_flow::try_visit!(v.#visit_method(self)) {
					visit_flow::try_visit!({ #body });
				}
				visit_flow::try_visit!(v.#exit_method(self));
			}
		} else {
			quote! { visit_flow::try_visit!({ #body }); }
		};