#![recursion_limit = "128"]
extern crate proc_macro;
use crate::proc_macro::TokenStream;
use quote::ToTokens;
use syn::{self, parse_macro_input, parse_quote, AttributeArgs, FnArg, ItemFn, Stmt};
#[proc_macro_attribute]
pub fn tracable_parser(attr: TokenStream, item: TokenStream) -> TokenStream {
let attr = parse_macro_input!(attr as AttributeArgs);
let item = parse_macro_input!(item as ItemFn);
impl_tracable_parser(&attr, &item)
}
fn impl_tracable_parser(_attr: &AttributeArgs, item: &ItemFn) -> TokenStream {
let default = impl_tracable_parser_default(&item);
let trace = impl_tracable_parser_trace(&item);
let mut item = item.clone();
item.block.stmts.clear();
item.block.stmts.push(default);
item.block.stmts.push(trace);
item.into_token_stream().into()
}
fn impl_tracable_parser_default(item: &ItemFn) -> Stmt {
let body = item.block.as_ref();
parse_quote! {
#[cfg(not(feature = "trace"))]
{
#body
}
}
}
fn impl_tracable_parser_trace(item: &ItemFn) -> Stmt {
let ident = &item.sig.ident;
let input = if let Some(x) = &item.sig.inputs.first() {
match x {
FnArg::Typed(arg) => &arg.pat,
_ => panic!("function with #[tracable_parser] must have an argument"),
}
} else {
panic!("function with #[tracable_parser] must have an argument");
};
let body = item.block.as_ref();
parse_quote! {
#[cfg(feature = "trace")]
{
let (depth, #input) = nom_tracable::forward_trace(#input, stringify!(#ident));
let body_ret = {
let body = || { #body };
body()
};
nom_tracable::backward_trace(body_ret, stringify!(#ident), depth)
}
}
}