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|
//! `mbe` (short for Macro By Example) crate contains code for handling
//! `macro_rules` macros. It uses `TokenTree` (from `ra_tt` package) as the
//! interface, although it contains some code to bridge `SyntaxNode`s and
//! `TokenTree`s as well!
mod parser;
mod mbe_expander;
mod syntax_bridge;
mod tt_iter;
mod subtree_source;
pub use tt::{Delimiter, Punct};
use crate::{
parser::{parse_pattern, Op},
tt_iter::TtIter,
};
#[derive(Debug, PartialEq, Eq)]
pub enum ParseError {
Expected(String),
}
#[derive(Debug, PartialEq, Eq)]
pub enum ExpandError {
NoMatchingRule,
UnexpectedToken,
BindingError(String),
ConversionError,
InvalidRepeat,
}
pub use crate::syntax_bridge::{
ast_to_token_tree, syntax_node_to_token_tree, token_tree_to_syntax_node, TokenMap,
};
/// This struct contains AST for a single `macro_rules` definition. What might
/// be very confusing is that AST has almost exactly the same shape as
/// `tt::TokenTree`, but there's a crucial difference: in macro rules, `$ident`
/// and `$()*` have special meaning (see `Var` and `Repeat` data structures)
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct MacroRules {
rules: Vec<Rule>,
/// Highest id of the token we have in TokenMap
shift: Shift,
}
#[derive(Clone, Debug, PartialEq, Eq)]
struct Rule {
lhs: tt::Subtree,
rhs: tt::Subtree,
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
struct Shift(u32);
impl Shift {
fn new(tt: &tt::Subtree) -> Shift {
// Note that TokenId is started from zero,
// We have to add 1 to prevent duplication.
let value = max_id(tt).map_or(0, |it| it + 1);
return Shift(value);
// Find the max token id inside a subtree
fn max_id(subtree: &tt::Subtree) -> Option<u32> {
subtree
.token_trees
.iter()
.filter_map(|tt| match tt {
tt::TokenTree::Subtree(subtree) => max_id(subtree),
tt::TokenTree::Leaf(tt::Leaf::Ident(ident))
if ident.id != tt::TokenId::unspecified() =>
{
Some(ident.id.0)
}
_ => None,
})
.max()
}
}
/// Shift given TokenTree token id
fn shift_all(self, tt: &mut tt::Subtree) {
for t in tt.token_trees.iter_mut() {
match t {
tt::TokenTree::Leaf(leaf) => match leaf {
tt::Leaf::Ident(ident) => ident.id = self.shift(ident.id),
_ => (),
},
tt::TokenTree::Subtree(tt) => self.shift_all(tt),
}
}
}
fn shift(self, id: tt::TokenId) -> tt::TokenId {
if id == tt::TokenId::unspecified() {
return id;
}
tt::TokenId(id.0 + self.0)
}
fn unshift(self, id: tt::TokenId) -> Option<tt::TokenId> {
id.0.checked_sub(self.0).map(tt::TokenId)
}
}
#[derive(Debug, Eq, PartialEq)]
pub enum Origin {
Def,
Call,
}
impl MacroRules {
pub fn parse(tt: &tt::Subtree) -> Result<MacroRules, ParseError> {
// Note: this parsing can be implemented using mbe machinery itself, by
// matching against `$($lhs:tt => $rhs:tt);*` pattern, but implementing
// manually seems easier.
let mut src = TtIter::new(tt);
let mut rules = Vec::new();
while src.len() > 0 {
let rule = Rule::parse(&mut src)?;
rules.push(rule);
if let Err(()) = src.expect_char(';') {
if src.len() > 0 {
return Err(ParseError::Expected("expected `:`".to_string()));
}
break;
}
}
for rule in rules.iter() {
validate(&rule.lhs)?;
}
Ok(MacroRules { rules, shift: Shift::new(tt) })
}
pub fn expand(&self, tt: &tt::Subtree) -> Result<tt::Subtree, ExpandError> {
// apply shift
let mut tt = tt.clone();
self.shift.shift_all(&mut tt);
mbe_expander::expand(self, &tt)
}
pub fn map_id_down(&self, id: tt::TokenId) -> tt::TokenId {
self.shift.shift(id)
}
pub fn map_id_up(&self, id: tt::TokenId) -> (tt::TokenId, Origin) {
match self.shift.unshift(id) {
Some(id) => (id, Origin::Call),
None => (id, Origin::Def),
}
}
}
impl Rule {
fn parse(src: &mut TtIter) -> Result<Rule, ParseError> {
let mut lhs = src
.expect_subtree()
.map_err(|()| ParseError::Expected("expected subtree".to_string()))?
.clone();
lhs.delimiter = None;
src.expect_char('=').map_err(|()| ParseError::Expected("expected `=`".to_string()))?;
src.expect_char('>').map_err(|()| ParseError::Expected("expected `>`".to_string()))?;
let mut rhs = src
.expect_subtree()
.map_err(|()| ParseError::Expected("expected subtree".to_string()))?
.clone();
rhs.delimiter = None;
Ok(crate::Rule { lhs, rhs })
}
}
fn validate(pattern: &tt::Subtree) -> Result<(), ParseError> {
for op in parse_pattern(pattern) {
let op = match op {
Ok(it) => it,
Err(e) => {
let msg = match e {
ExpandError::InvalidRepeat => "invalid repeat".to_string(),
_ => "invalid macro definition".to_string(),
};
return Err(ParseError::Expected(msg));
}
};
match op {
Op::TokenTree(tt::TokenTree::Subtree(subtree)) | Op::Repeat { subtree, .. } => {
validate(subtree)?
}
_ => (),
}
}
Ok(())
}
#[cfg(test)]
mod tests;
|
