48 lines
1.3 KiB
Rust
48 lines
1.3 KiB
Rust
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use quote::{ToTokens, quote};
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use syn::spanned::Spanned;
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pub struct All {
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name: syn::Ident,
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variants: Box<[syn::Ident]>,
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}
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impl All {
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pub fn parse(input: syn::DeriveInput) -> Result<Self, syn::Error> {
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let data = match input.data {
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syn::Data::Enum(enu) => enu,
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_ => {
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return Err(syn::Error::new(
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input.span(),
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"All can only be used on enums",
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));
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}
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};
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let variants = data
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.variants
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.into_iter()
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.map(|v| match &v.fields {
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syn::Fields::Named(_) | syn::Fields::Unnamed(_) => Err(syn::Error::new(
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v.ident.span(),
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"All can only be used on enums with only unit fields",
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)),
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syn::Fields::Unit => Ok(v.ident),
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})
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.collect::<Result<Box<[_]>, _>>()?;
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let name = input.ident;
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Ok(Self { name, variants })
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}
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}
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impl ToTokens for All {
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fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
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let name = &self.name;
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let variants = &self.variants;
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let count = self.variants.len();
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tokens.extend(quote! {
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impl #name {
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pub const ALL: [#name; #count] = [#(#name::#variants),*];
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}
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});
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}
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}
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