schala/schala-lang/codegen/src/lib.rs

#![feature(box_patterns)]
extern crate proc_macro;
#[macro_use]
extern crate quote;
#[macro_use]
extern crate syn;

use self::proc_macro::TokenStream;
use self::syn::fold::Fold;

struct RecursiveDescentFn {
}

impl Fold for RecursiveDescentFn {
  fn fold_item_fn(&mut self, mut i: syn::ItemFn) -> syn::ItemFn {
    let box block = i.block;
    let mut stmts = block.stmts;
    let new_item: syn::Stmt = parse_quote! {
      println!("FROM PROC MACRO");
    };
    let mut new_stmts = vec![new_item];
    new_stmts.append(&mut stmts);
    let new_block = syn::Block { brace_token: block.brace_token, stmts: new_stmts };
    i.block = Box::new(new_block);
    i
  }
}

#[proc_macro_attribute]
pub fn recursive_descent_method(attr: TokenStream, item: TokenStream) -> TokenStream {

  let input: syn::ItemFn = parse_macro_input!(item as syn::ItemFn);
  let mut folder = RecursiveDescentFn {};
  let output = folder.fold_item_fn(input);
  TokenStream::from(quote!(#output))
}