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//! Ungrammar -- a DSL for specifying concrete syntax tree grammar.
//!
//! Producing a parser is an explicit non-goal -- it's ok for this grammar to be
//! ambiguous, non LL, non LR, etc.
//!
//! See this
//! [introductory post](https://rust-analyzer.github.io/blog/2020/10/24/introducing-ungrammar.html)
//! for details.
#![deny(missing_debug_implementations)]
#![deny(missing_docs)]
#![deny(rust_2018_idioms)]
mod error;
mod lexer;
mod parser;
use std::{ops, str::FromStr};
pub use error::{Error, Result};
/// Returns a Rust grammar.
pub fn rust_grammar() -> Grammar {
let src = include_str!("../rust.ungram");
src.parse().unwrap()
}
/// A node, like `A = 'b' | 'c'`.
///
/// Indexing into a [`Grammar`] with a [`Node`] returns a reference to a
/// [`NodeData`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Node(usize);
/// A token, denoted with single quotes, like `'+'` or `'struct'`.
///
/// Indexing into a [`Grammar`] with a [`Token`] returns a reference to a
/// [`TokenData`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Token(usize);
/// An Ungrammar grammar.
#[derive(Default, Debug)]
pub struct Grammar {
nodes: Vec<NodeData>,
tokens: Vec<TokenData>,
}
impl FromStr for Grammar {
type Err = Error;
fn from_str(s: &str) -> Result<Self> {
let tokens = lexer::tokenize(s)?;
parser::parse(tokens)
}
}
impl Grammar {
/// Returns an iterator over all nodes in the grammar.
pub fn iter(&self) -> impl Iterator<Item = Node> + '_ {
(0..self.nodes.len()).map(Node)
}
/// Returns an iterator over all tokens in the grammar.
pub fn tokens(&self) -> impl Iterator<Item = Token> + '_ {
(0..self.tokens.len()).map(Token)
}
}
impl ops::Index<Node> for Grammar {
type Output = NodeData;
fn index(&self, Node(index): Node) -> &NodeData {
&self.nodes[index]
}
}
impl ops::Index<Token> for Grammar {
type Output = TokenData;
fn index(&self, Token(index): Token) -> &TokenData {
&self.tokens[index]
}
}
/// Data about a node.
#[derive(Debug)]
pub struct NodeData {
/// The name of the node.
///
/// In the rule `A = 'b' | 'c'`, this is `"A"`.
pub name: String,
/// The rule for this node.
///
/// In the rule `A = 'b' | 'c'`, this represents `'b' | 'c'`.
pub rule: Rule,
}
/// Data about a token.
#[derive(Debug)]
pub struct TokenData {
/// The name of the token.
pub name: String,
}
/// A production rule.
#[derive(Debug, Eq, PartialEq)]
pub enum Rule {
/// A labeled rule, like `a:B` (`"a"` is the label, `B` is the rule).
Labeled {
/// The label.
label: String,
/// The rule.
rule: Box<Rule>,
},
/// A node, like `A`.
Node(Node),
/// A token, like `'struct'`.
Token(Token),
/// A sequence of rules, like `'while' '(' Expr ')' Stmt`.
Seq(Vec<Rule>),
/// An alternative between many rules, like `'+' | '-' | '*' | '/'`.
Alt(Vec<Rule>),
/// An optional rule, like `A?`.
Opt(Box<Rule>),
/// A repeated rule, like `A*`.
Rep(Box<Rule>),
}
#[test]
fn smoke() {
let grammar = include_str!("../ungrammar.ungram");
let grammar = grammar.parse::<Grammar>().unwrap();
drop(grammar)
}
#[test]
fn test_rust_grammar() {
let _ = rust_grammar();
}
|
