enumtrait 1.0.0

A library of macros for polymorphism using enums
Documentation 
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use combi::{
    choices,
    core::{choice, mapsuc, seq},
    macros::seqs,
    tokens::{
        basic::{getident, matchident, peekident},
        TokenDiagnostic, TokenIter,
    },
    Combi,
};
use proc_macro2::{Ident, Span, TokenStream};
use proc_macro_error2::Diagnostic;
use quote::quote;
use std::collections::LinkedList;

pub fn interface(
    attr: TokenStream,
    item: TokenStream,
) -> Result<TokenStream, LinkedList<Diagnostic>> {
    let (macro_name, vis) = parse_attrs(attr)?;
    let doc_message = format!(
        "Generated by [enumtrait] to store the tokens: 
```ignore
{item}
```"
    );
    let macro_tks = quote! {
        #[doc = #doc_message]
        macro_rules! #macro_name {
            (expr_ctx $p:ident => $($t:tt)*) => { // if expression context, no ; is required
                $p!( $($t)* { #macro_name { #item } } )
            };
            (item_ctx $p:path => $($t:tt)*) => { // if being used in an item context, need to end with ; or use macro!{ }
                $p!( $($t)* { #macro_name { #item } } );
            };
        }
    };

    let (export_tks, pub_tks) = match vis {
        Attr::Pub(p) => (quote! {}, quote! {#p(crate) use #macro_name;}),
        Attr::Export(e) => {
            let export = Ident::new("macro_export", e.span());
            (quote! {#[#export]}, quote! {pub use #macro_name;})
        }
        Attr::None => (quote!(), quote!()),
    };

    Ok(quote! {
        #item
        #export_tks
        #macro_tks
        #pub_tks
    })
}

enum Attr {
    Pub(Ident),
    Export(Ident),
    None,
}

fn parse_attrs(attr: TokenStream) -> Result<(Ident, Attr), LinkedList<Diagnostic>> {
    let parser = choices! {
        peekident("pub") => mapsuc(seqs!(matchident("pub"), getident()), |(p, i)| (i, Attr::Pub(p))),
        peekident("export") => mapsuc(seqs!(matchident("export"), getident()), |(e, i)| (i, Attr::Export(e))),
        otherwise => mapsuc(getident(), |i| (i, Attr::None))
    };
    let (_, res) = parser.comp(TokenIter::from(attr, Span::call_site()));
    res.to_result().map_err(TokenDiagnostic::into_list)
}