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|
use proc_macro2::TokenStream;
use quote::{format_ident, quote, quote_spanned};
use syn::spanned::Spanned;
use syn::{Data, Fields, Ident};
use synstructure::Structure;
fn print_fields(name: &Ident, fields: &Fields) -> (TokenStream, TokenStream) {
let string_name = name.to_string();
let mut disps = vec![quote! {let mut __printed_anything = false;}];
match fields {
Fields::Named(fields_named) => {
let mut field_names = Vec::new();
for field in &fields_named.named {
let name = field.ident.as_ref().unwrap();
let string_name = name.to_string();
disps.push(quote! {
if #name.should_render() {
if __printed_anything {
__p.word_space(",");
}
__p.word(#string_name);
__p.word(":");
__p.nbsp();
__printed_anything = true;
}
#name.print_attribute(__p);
});
field_names.push(name);
}
(
quote! { {#(#field_names),*} },
quote! {
__p.word(#string_name);
if true #(&& !#field_names.should_render())* {
return;
}
__p.nbsp();
__p.word("{");
#(#disps)*
__p.word("}");
},
)
}
Fields::Unnamed(fields_unnamed) => {
let mut field_names = Vec::new();
for idx in 0..fields_unnamed.unnamed.len() {
let name = format_ident!("f{idx}");
disps.push(quote! {
if #name.should_render() {
if __printed_anything {
__p.word_space(",");
}
__printed_anything = true;
}
#name.print_attribute(__p);
});
field_names.push(name);
}
(
quote! { (#(#field_names),*) },
quote! {
__p.word(#string_name);
if true #(&& !#field_names.should_render())* {
return;
}
__p.popen();
#(#disps)*
__p.pclose();
},
)
}
Fields::Unit => (quote! {}, quote! { __p.word(#string_name) }),
}
}
pub(crate) fn print_attribute(input: Structure<'_>) -> TokenStream {
let span_error = |span, message: &str| {
quote_spanned! { span => const _: () = ::core::compile_error!(#message); }
};
// Must be applied to an enum type.
let code = match &input.ast().data {
Data::Enum(e) => {
let arms = e
.variants
.iter()
.map(|x| {
let ident = &x.ident;
let (pat, code) = print_fields(ident, &x.fields);
quote! {
Self::#ident #pat => {#code}
}
})
.collect::<Vec<_>>();
quote! {
match self {
#(#arms)*
}
}
}
Data::Struct(s) => {
let (pat, code) = print_fields(&input.ast().ident, &s.fields);
quote! {
let Self #pat = self;
#code
}
}
Data::Union(u) => {
return span_error(u.union_token.span(), "can't derive PrintAttribute on unions");
}
};
#[allow(keyword_idents_2024)]
input.gen_impl(quote! {
#[allow(unused)]
gen impl PrintAttribute for @Self {
fn should_render(&self) -> bool { true }
fn print_attribute(&self, __p: &mut rustc_ast_pretty::pp::Printer) { #code }
}
})
}
|
