rust/crates/mbe/src/parser.rs

271 lines
8.8 KiB
Rust

//! Parser recognizes special macro syntax, `$var` and `$(repeat)*`, in token
//! trees.
use smallvec::SmallVec;
use syntax::SmolStr;
use tt::Delimiter;
use crate::{tt_iter::TtIter, ParseError};
#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) struct MetaTemplate(pub(crate) Vec<Op>);
#[derive(Debug, Clone, Copy)]
pub(crate) enum OpDelimited<'a> {
Op(&'a Op),
Open,
Close,
}
#[derive(Debug, Clone, Copy)]
pub(crate) struct OpDelimitedIter<'a> {
inner: &'a Vec<Op>,
delimited: Option<&'a Delimiter>,
idx: usize,
}
impl<'a> OpDelimitedIter<'a> {
pub(crate) fn is_eof(&self) -> bool {
let len = self.inner.len() + if self.delimited.is_some() { 2 } else { 0 };
self.idx >= len
}
pub(crate) fn peek(&self) -> Option<OpDelimited<'a>> {
match self.delimited {
None => self.inner.get(self.idx).map(OpDelimited::Op),
Some(_) => match self.idx {
0 => Some(OpDelimited::Open),
i if i == self.inner.len() + 1 => Some(OpDelimited::Close),
i => self.inner.get(i - 1).map(OpDelimited::Op),
},
}
}
pub(crate) fn reset(&self) -> Self {
Self { inner: &self.inner, idx: 0, delimited: self.delimited }
}
}
impl<'a> Iterator for OpDelimitedIter<'a> {
type Item = OpDelimited<'a>;
fn next(&mut self) -> Option<Self::Item> {
let res = self.peek();
self.idx += 1;
res
}
fn size_hint(&self) -> (usize, Option<usize>) {
let len = self.inner.len() + if self.delimited.is_some() { 2 } else { 0 };
let remain = len.checked_sub(self.idx).unwrap_or(0);
(remain, Some(remain))
}
}
impl<'a> MetaTemplate {
pub(crate) fn iter(&self) -> impl Iterator<Item = &Op> {
self.0.iter()
}
pub(crate) fn iter_delimited(
&'a self,
delimited: Option<&'a Delimiter>,
) -> OpDelimitedIter<'a> {
OpDelimitedIter { inner: &self.0, idx: 0, delimited }
}
}
#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) enum Op {
Var { name: SmolStr, kind: Option<SmolStr>, id: tt::TokenId },
Repeat { tokens: MetaTemplate, kind: RepeatKind, separator: Option<Separator> },
Leaf(tt::Leaf),
Subtree { tokens: MetaTemplate, delimiter: Option<Delimiter> },
}
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub(crate) enum RepeatKind {
ZeroOrMore,
OneOrMore,
ZeroOrOne,
}
#[derive(Clone, Debug, Eq)]
pub(crate) enum Separator {
Literal(tt::Literal),
Ident(tt::Ident),
Puncts(SmallVec<[tt::Punct; 3]>),
}
// Note that when we compare a Separator, we just care about its textual value.
impl PartialEq for Separator {
fn eq(&self, other: &Separator) -> bool {
use Separator::*;
match (self, other) {
(Ident(ref a), Ident(ref b)) => a.text == b.text,
(Literal(ref a), Literal(ref b)) => a.text == b.text,
(Puncts(ref a), Puncts(ref b)) if a.len() == b.len() => {
let a_iter = a.iter().map(|a| a.char);
let b_iter = b.iter().map(|b| b.char);
a_iter.eq(b_iter)
}
_ => false,
}
}
}
impl Separator {
pub(crate) fn tt_count(&self) -> usize {
match self {
Separator::Literal(_) => 1,
Separator::Ident(_) => 1,
Separator::Puncts(it) => it.len(),
}
}
}
pub(crate) fn parse_template(template: &tt::Subtree) -> Result<Vec<Op>, ParseError> {
parse_inner(&template, Mode::Template).into_iter().collect()
}
pub(crate) fn parse_pattern(pattern: &tt::Subtree) -> Result<Vec<Op>, ParseError> {
parse_inner(&pattern, Mode::Pattern).into_iter().collect()
}
#[derive(Clone, Copy)]
enum Mode {
Pattern,
Template,
}
fn parse_inner(tt: &tt::Subtree, mode: Mode) -> Vec<Result<Op, ParseError>> {
let mut src = TtIter::new(&tt);
std::iter::from_fn(move || {
let first = src.next()?;
Some(next_op(first, &mut src, mode))
})
.collect()
}
macro_rules! err {
($($tt:tt)*) => {
ParseError::UnexpectedToken(($($tt)*).to_string())
};
}
macro_rules! bail {
($($tt:tt)*) => {
return Err(err!($($tt)*))
};
}
fn next_op<'a>(first: &tt::TokenTree, src: &mut TtIter<'a>, mode: Mode) -> Result<Op, ParseError> {
let res = match first {
tt::TokenTree::Leaf(leaf @ tt::Leaf::Punct(tt::Punct { char: '$', .. })) => {
// Note that the '$' itself is a valid token inside macro_rules.
let second = match src.next() {
None => return Ok(Op::Leaf(leaf.clone())),
Some(it) => it,
};
match second {
tt::TokenTree::Subtree(subtree) => {
let (separator, kind) = parse_repeat(src)?;
let tokens = parse_inner(&subtree, mode)
.into_iter()
.collect::<Result<Vec<Op>, ParseError>>()?;
Op::Repeat { tokens: MetaTemplate(tokens), separator, kind }
}
tt::TokenTree::Leaf(leaf) => match leaf {
tt::Leaf::Punct(_) => {
return Err(ParseError::Expected("ident".to_string()));
}
tt::Leaf::Ident(ident) if ident.text == "crate" => {
// We simply produce identifier `$crate` here. And it will be resolved when lowering ast to Path.
Op::Leaf(tt::Leaf::from(tt::Ident { text: "$crate".into(), id: ident.id }))
}
tt::Leaf::Ident(ident) => {
let name = ident.text.clone();
let kind = eat_fragment_kind(src, mode)?;
let id = ident.id;
Op::Var { name, kind, id }
}
tt::Leaf::Literal(lit) => {
if is_boolean_literal(&lit) {
let name = lit.text.clone();
let kind = eat_fragment_kind(src, mode)?;
let id = lit.id;
Op::Var { name, kind, id }
} else {
bail!("bad var 2");
}
}
},
}
}
tt::TokenTree::Leaf(tt) => Op::Leaf(tt.clone()),
tt::TokenTree::Subtree(subtree) => {
let tokens =
parse_inner(&subtree, mode).into_iter().collect::<Result<Vec<Op>, ParseError>>()?;
Op::Subtree { tokens: MetaTemplate(tokens), delimiter: subtree.delimiter }
}
};
Ok(res)
}
fn eat_fragment_kind<'a>(src: &mut TtIter<'a>, mode: Mode) -> Result<Option<SmolStr>, ParseError> {
if let Mode::Pattern = mode {
src.expect_char(':').map_err(|()| err!("bad fragment specifier 1"))?;
let ident = src.expect_ident().map_err(|()| err!("bad fragment specifier 1"))?;
return Ok(Some(ident.text.clone()));
};
Ok(None)
}
fn is_boolean_literal(lit: &tt::Literal) -> bool {
matches!(lit.text.as_str(), "true" | "false")
}
fn parse_repeat(src: &mut TtIter) -> Result<(Option<Separator>, RepeatKind), ParseError> {
let mut separator = Separator::Puncts(SmallVec::new());
for tt in src {
let tt = match tt {
tt::TokenTree::Leaf(leaf) => leaf,
tt::TokenTree::Subtree(_) => return Err(ParseError::InvalidRepeat),
};
let has_sep = match &separator {
Separator::Puncts(puncts) => !puncts.is_empty(),
_ => true,
};
match tt {
tt::Leaf::Ident(_) | tt::Leaf::Literal(_) if has_sep => {
return Err(ParseError::InvalidRepeat)
}
tt::Leaf::Ident(ident) => separator = Separator::Ident(ident.clone()),
tt::Leaf::Literal(lit) => separator = Separator::Literal(lit.clone()),
tt::Leaf::Punct(punct) => {
let repeat_kind = match punct.char {
'*' => RepeatKind::ZeroOrMore,
'+' => RepeatKind::OneOrMore,
'?' => RepeatKind::ZeroOrOne,
_ => {
match &mut separator {
Separator::Puncts(puncts) => {
if puncts.len() == 3 {
return Err(ParseError::InvalidRepeat);
}
puncts.push(*punct)
}
_ => return Err(ParseError::InvalidRepeat),
}
continue;
}
};
let separator = if has_sep { Some(separator) } else { None };
return Ok((separator, repeat_kind));
}
}
}
Err(ParseError::InvalidRepeat)
}