| // WARNING WARNING WARNING WARNING WARNING |
| // ======================================= |
| // |
| // This code also appears in src/doc/unstable-book/src/language-features/plugin.md. |
| // Please keep the two copies in sync! FIXME: have rustdoc read this file |
| |
| // force-host |
| |
| #![crate_type="dylib"] |
| #![feature(plugin_registrar, rustc_private)] |
| |
| extern crate syntax; |
| extern crate syntax_pos; |
| extern crate rustc; |
| extern crate rustc_driver; |
| |
| use syntax::parse::token::{self, Token}; |
| use syntax::tokenstream::TokenTree; |
| use syntax::ext::base::{ExtCtxt, MacResult, DummyResult, MacEager}; |
| use syntax_pos::Span; |
| use rustc_driver::plugin::Registry; |
| |
| fn expand_rn(cx: &mut ExtCtxt, sp: Span, args: &[TokenTree]) |
| -> Box<dyn MacResult + 'static> { |
| |
| static NUMERALS: &'static [(&'static str, usize)] = &[ |
| ("M", 1000), ("CM", 900), ("D", 500), ("CD", 400), |
| ("C", 100), ("XC", 90), ("L", 50), ("XL", 40), |
| ("X", 10), ("IX", 9), ("V", 5), ("IV", 4), |
| ("I", 1)]; |
| |
| if args.len() != 1 { |
| cx.span_err( |
| sp, |
| &format!("argument should be a single identifier, but got {} arguments", args.len())); |
| return DummyResult::any(sp); |
| } |
| |
| let text = match args[0] { |
| TokenTree::Token(Token { kind: token::Ident(s, _), .. }) => s.to_string(), |
| _ => { |
| cx.span_err(sp, "argument should be a single identifier"); |
| return DummyResult::any(sp); |
| } |
| }; |
| |
| let mut text = &*text; |
| let mut total = 0; |
| while !text.is_empty() { |
| match NUMERALS.iter().find(|&&(rn, _)| text.starts_with(rn)) { |
| Some(&(rn, val)) => { |
| total += val; |
| text = &text[rn.len()..]; |
| } |
| None => { |
| cx.span_err(sp, "invalid Roman numeral"); |
| return DummyResult::any(sp); |
| } |
| } |
| } |
| |
| MacEager::expr(cx.expr_usize(sp, total)) |
| } |
| |
| #[plugin_registrar] |
| pub fn plugin_registrar(reg: &mut Registry) { |
| reg.register_macro("rn", expand_rn); |
| } |