IdentTT

Cargo.toml

[package]
name = "identtt"
version = "0.0.1"

[lib]
name = "identtt_ext"
path = "lib.rs"
plugin = true
crate-type = ["dylib"]

[[bin]]
name = "identtt"
path = "main.rs"

lib.rs

#![allow(unstable)]
#![feature(box_syntax, plugin_registrar)]

extern crate rustc;
extern crate syntax;

use std::ascii::AsciiExt;
use rustc::plugin::Registry;
use syntax::ast;
use syntax::ast_util;
use syntax::codemap::{DUMMY_SP, Span};
use syntax::ext::base;
use syntax::ext::build::AstBuilder;
use syntax::parse::common::SeqSep;
use syntax::parse::token;
use syntax::ptr::P;

#[plugin_registrar]
pub fn plugin_registrar(reg: &mut Registry) {
    let expander: base::IdentMacroExpanderFn = expand_upper_enum;
    reg.register_syntax_extension(
        token::intern("upper_enum"),
        base::IdentTT(box expander, None)
    );
}

fn expand_upper_enum(cx: &mut base::ExtCtxt, sp: Span, ident: ast::Ident, args: Vec<ast::TokenTree>) -> Box<base::MacResult + 'static> {
    let members = cx.new_parser_from_tts(&args[])
    .parse_seq_to_end(
        &token::Eof,
        SeqSep {
            sep: Some(token::Comma),
            trailing_sep_allowed: true
        },
        |p| {
            let span = p.span;
            let id = p.parse_ident().as_str().to_ascii_uppercase();
            P(cx.variant(span, cx.ident_of(&id[]), Vec::new()))
        }
    );
    let attr = cx.attribute(DUMMY_SP, cx.meta_list(
        DUMMY_SP,
        token::InternedString::new("derive"),
        vec![cx.meta_word(DUMMY_SP, token::InternedString::new("Show"))]
    ));
    let item = cx.item(sp, ident, vec![attr],
        ast::ItemEnum(
            ast::EnumDef { variants: members },
            ast_util::empty_generics()
        )
    );
    base::MacItems::new(vec![item].into_iter())
}

main.rs

#![feature(plugin)]

#[plugin]
#[no_link]
extern crate identtt_ext;

upper_enum! Nemui {
    Meccha, SorehodoDemonai
}

fn main() {
    println!("{:?}, {:?}",
        Nemui::MECCHA, Nemui::SOREHODODEMONAI);
}