lalrpop 0.12.2

convenient LR(1) parser generator
Documentation 
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//! A compiler from an LR(1) table to a [recursive ascent] parser.
//!
//! [recursive ascent]: https://en.wikipedia.org/wiki/Recursive_ascent_parser

use grammar::repr::{Grammar, NonterminalString, TypeParameter};
use lr1::core::*;
use rust::RustWrite;
use std::io::{self, Write};
use util::Sep;

use super::base::CodeGenerator;

pub fn compile<'grammar, W: Write>(grammar: &'grammar Grammar,
                                   user_start_symbol: NonterminalString,
                                   start_symbol: NonterminalString,
                                   states: &[LR1State<'grammar>],
                                   out: &mut RustWrite<W>)
                                   -> io::Result<()> {
    let mut ascent = CodeGenerator::new_test_all(grammar,
                                                 user_start_symbol,
                                                 start_symbol,
                                                 states,
                                                 out);
    ascent.write()
}

struct TestAll;

impl<'ascent, 'grammar, W: Write> CodeGenerator<'ascent, 'grammar, W, TestAll> {
    fn new_test_all(grammar: &'grammar Grammar,
                    user_start_symbol: NonterminalString,
                    start_symbol: NonterminalString,
                    states: &'ascent [LR1State<'grammar>],
                    out: &'ascent mut RustWrite<W>)
                    -> Self {
        CodeGenerator::new(grammar,
                           user_start_symbol,
                           start_symbol,
                           states,
                           out,
                           true,
                           "super",
                           TestAll)
    }

    fn write(&mut self) -> io::Result<()> {
        self.write_parse_mod(|this| {
            try!(this.write_parser_fn());

            rust!(this.out, "mod {}ascent {{", this.prefix);
            try!(super::ascent::compile(this.grammar,
                                        this.user_start_symbol,
                                        this.start_symbol,
                                        this.states,
                                        "super::super::super",
                                        this.out));
            rust!(this.out,
                  "pub use self::{}parse{}::parse_{};",
                  this.prefix,
                  this.start_symbol,
                  this.user_start_symbol);
            rust!(this.out, "}}");

            rust!(this.out, "mod {}parse_table {{", this.prefix);
            try!(super::parse_table::compile(this.grammar,
                                             this.user_start_symbol,
                                             this.start_symbol,
                                             this.states,
                                             "super::super::super",
                                             this.out));
            rust!(this.out,
                  "pub use self::{}parse{}::parse_{};",
                  this.prefix,
                  this.start_symbol,
                  this.user_start_symbol);
            rust!(this.out, "}}");

            Ok(())
        })
    }

    fn write_parser_fn(&mut self) -> io::Result<()> {
        try!(self.start_parser_fn());

        // parse input using both methods:
        try!(self.call_delegate("ascent"));
        try!(self.call_delegate("parse_table"));

        // check that result is the same either way:
        rust!(self.out,
              "assert_eq!({}ascent, {}parse_table);",
              self.prefix,
              self.prefix);

        rust!(self.out, "return {}ascent;", self.prefix);

        try!(self.end_parser_fn());

        Ok(())
    }

    fn call_delegate(&mut self, delegate: &str) -> io::Result<()> {
        let non_lifetimes: Vec<_> =
            self.grammar.type_parameters
                        .iter()
                        .filter(|&tp| match *tp {
                            TypeParameter::Lifetime(_) => false,
                            TypeParameter::Id(_) => true,
                        })
                        .cloned()
                        .collect();
        let parameters = if non_lifetimes.is_empty() {
            String::new()
        } else {
            format!("::<{}>", Sep(", ", &non_lifetimes))
        };
        rust!(self.out,
              "let {}{} = {}{}::parse_{}{}(",
              self.prefix,
              delegate,
              self.prefix,
              delegate,
              self.user_start_symbol,
              parameters);
        for parameter in &self.grammar.parameters {
            rust!(self.out, "{},", parameter.name);
        }
        if self.grammar.intern_token.is_none() {
            rust!(self.out, "{}tokens0.clone(),", self.prefix);
        }
        rust!(self.out, ");");
        Ok(())
    }
}