pleme-closedaxis-derive 0.1.0

Enum-fold derive proc-macro emitted from a tatara-rust-derive EnumFoldDeriveSpec.
Documentation 
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//!GENERATED by tatara-rust-derive::EnumFoldDeriveSpec.
//!Do not hand-edit; regenerate from the (defenum-fold …) source.
use proc_macro::TokenStream;
use quote::quote;
use syn::{Data, DataEnum, DeriveInput, Fields, parse_macro_input};
#[proc_macro_derive(ClosedAxis)]
pub fn derive_closed_axis(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    let self_name = &input.ident;
    let de = match &input.data {
        Data::Enum(de) => de,
        _ => {
            return syn::Error::new_spanned(self_name, "EnumFoldDerive requires an enum")
                .to_compile_error()
                .into();
        }
    };
    for v in &de.variants {
        if !matches!(v.fields, Fields::Unit) {
            return syn::Error::new_spanned(
                    &v.ident,
                    "EnumFoldDerive (unit-only) requires all variants be unit variants",
                )
                .to_compile_error()
                .into();
        }
    }
    let fold_count = de.variants.len();
    let fold_count_lit = proc_macro2::Literal::usize_unsuffixed(fold_count);
    let _ = fold_count_lit.clone();
    let fragments: Vec<_> = de
        .variants
        .iter()
        .map(|v| {
            let variant_name = &v.ident;
            let variant_str = variant_name.to_string();
            quote! {
                Self::# variant_name
            }
        })
        .collect();
    let _ = &fragments;
    let expanded = quote! {
        impl # self_name { pub const ALL : &'static [Self] = & [# (# fragments),*]; }
        impl ::shikumi::ClosedAxis for # self_name { const ALL : &'static [Self] = & [#
        (# fragments),*]; }
    };
    TokenStream::from(expanded)
}