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