88 lines
3.0 KiB
Rust
88 lines
3.0 KiB
Rust
use synstructure;
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use syn::{self, Meta, NestedMeta};
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use proc_macro2::{self, Ident, Span};
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struct Attributes {
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ignore: bool,
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project: Option<String>,
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}
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fn parse_attributes(field: &syn::Field) -> Attributes {
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let mut attrs = Attributes {
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ignore: false,
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project: None,
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};
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for attr in &field.attrs {
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if let Ok(meta) = attr.parse_meta() {
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if &meta.name().to_string() != "stable_hasher" {
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continue;
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}
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let mut any_attr = false;
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if let Meta::List(list) = meta {
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for nested in list.nested.iter() {
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if let NestedMeta::Meta(meta) = nested {
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if &meta.name().to_string() == "ignore" {
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attrs.ignore = true;
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any_attr = true;
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}
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if &meta.name().to_string() == "project" {
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if let Meta::List(list) = meta {
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if let Some(nested) = list.nested.iter().next() {
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if let NestedMeta::Meta(meta) = nested {
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attrs.project = Some(meta.name().to_string());
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any_attr = true;
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}
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}
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}
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}
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}
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}
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}
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if !any_attr {
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panic!("error parsing stable_hasher");
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}
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}
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}
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attrs
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}
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pub fn hash_stable_derive(mut s: synstructure::Structure) -> proc_macro2::TokenStream {
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let generic: syn::GenericParam = parse_quote!('__ctx);
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s.add_bounds(synstructure::AddBounds::Generics);
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s.add_impl_generic(generic);
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let body = s.each(|bi| {
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let attrs = parse_attributes(bi.ast());
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if attrs.ignore {
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quote!{}
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} else if let Some(project) = attrs.project {
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let project = Ident::new(&project, Span::call_site());
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quote!{
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&#bi.#project.hash_stable(__hcx, __hasher);
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}
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} else {
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quote!{
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#bi.hash_stable(__hcx, __hasher);
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}
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}
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});
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let discriminant = match s.ast().data {
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syn::Data::Enum(_) => quote! {
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::std::mem::discriminant(self).hash_stable(__hcx, __hasher);
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},
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syn::Data::Struct(_) => quote! {},
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syn::Data::Union(_) => panic!("cannot derive on union"),
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};
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s.bound_impl(quote!(::rustc_data_structures::stable_hasher::HashStable
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<::rustc::ich::StableHashingContext<'__ctx>>), quote!{
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fn hash_stable<__W: ::rustc_data_structures::stable_hasher::StableHasherResult>(
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&self,
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__hcx: &mut ::rustc::ich::StableHashingContext<'__ctx>,
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__hasher: &mut ::rustc_data_structures::stable_hasher::StableHasher<__W>) {
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#discriminant
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match *self { #body }
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}
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})
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}
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