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|
//! A "Parser" structure for token trees. We use this when parsing a declarative
//! macro definition into a list of patterns and templates.
use syntax::SyntaxKind;
use tt::buffer::TokenBuffer;
use crate::{to_parser_input::to_parser_input, ExpandError, ExpandResult};
#[derive(Debug, Clone)]
pub(crate) struct TtIter<'a> {
pub(crate) inner: std::slice::Iter<'a, tt::TokenTree>,
}
impl<'a> TtIter<'a> {
pub(crate) fn new(subtree: &'a tt::Subtree) -> TtIter<'a> {
TtIter { inner: subtree.token_trees.iter() }
}
pub(crate) fn expect_char(&mut self, char: char) -> Result<(), ()> {
match self.next() {
Some(&tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: c, .. }))) if c == char => {
Ok(())
}
_ => Err(()),
}
}
pub(crate) fn expect_any_char(&mut self, chars: &[char]) -> Result<(), ()> {
match self.next() {
Some(tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: c, .. })))
if chars.contains(c) =>
{
Ok(())
}
_ => Err(()),
}
}
pub(crate) fn expect_subtree(&mut self) -> Result<&'a tt::Subtree, ()> {
match self.next() {
Some(tt::TokenTree::Subtree(it)) => Ok(it),
_ => Err(()),
}
}
pub(crate) fn expect_leaf(&mut self) -> Result<&'a tt::Leaf, ()> {
match self.next() {
Some(tt::TokenTree::Leaf(it)) => Ok(it),
_ => Err(()),
}
}
pub(crate) fn expect_ident(&mut self) -> Result<&'a tt::Ident, ()> {
match self.expect_leaf()? {
tt::Leaf::Ident(it) if it.text != "_" => Ok(it),
_ => Err(()),
}
}
pub(crate) fn expect_ident_or_underscore(&mut self) -> Result<&'a tt::Ident, ()> {
match self.expect_leaf()? {
tt::Leaf::Ident(it) => Ok(it),
_ => Err(()),
}
}
pub(crate) fn expect_literal(&mut self) -> Result<&'a tt::Leaf, ()> {
let it = self.expect_leaf()?;
match it {
tt::Leaf::Literal(_) => Ok(it),
tt::Leaf::Ident(ident) if ident.text == "true" || ident.text == "false" => Ok(it),
_ => Err(()),
}
}
pub(crate) fn expect_u32_literal(&mut self) -> Result<u32, ()> {
match self.expect_literal()? {
tt::Leaf::Literal(lit) => lit.text.parse().map_err(drop),
_ => Err(()),
}
}
pub(crate) fn expect_punct(&mut self) -> Result<&'a tt::Punct, ()> {
match self.expect_leaf()? {
tt::Leaf::Punct(it) => Ok(it),
_ => Err(()),
}
}
pub(crate) fn expect_fragment(
&mut self,
entry_point: parser::PrefixEntryPoint,
) -> ExpandResult<Option<tt::TokenTree>> {
let buffer = TokenBuffer::from_tokens(self.inner.as_slice());
let parser_input = to_parser_input(&buffer);
let tree_traversal = entry_point.parse(&parser_input);
let mut cursor = buffer.begin();
let mut error = false;
for step in tree_traversal.iter() {
match step {
parser::Step::Token { kind, mut n_input_tokens } => {
if kind == SyntaxKind::LIFETIME_IDENT {
n_input_tokens = 2;
}
for _ in 0..n_input_tokens {
cursor = cursor.bump_subtree();
}
}
parser::Step::Enter { .. } | parser::Step::Exit => (),
parser::Step::Error { .. } => error = true,
}
}
let err = if error || !cursor.is_root() {
Some(ExpandError::binding_error(format!("expected {entry_point:?}")))
} else {
None
};
let mut curr = buffer.begin();
let mut res = vec![];
if cursor.is_root() {
while curr != cursor {
if let Some(token) = curr.token_tree() {
res.push(token);
}
curr = curr.bump();
}
}
self.inner = self.inner.as_slice()[res.len()..].iter();
let res = match res.len() {
1 => Some(res[0].cloned()),
0 => None,
_ => Some(tt::TokenTree::Subtree(tt::Subtree {
delimiter: None,
token_trees: res.into_iter().map(|it| it.cloned()).collect(),
})),
};
ExpandResult { value: res, err }
}
pub(crate) fn peek_n(&self, n: usize) -> Option<&tt::TokenTree> {
self.inner.as_slice().get(n)
}
}
impl<'a> Iterator for TtIter<'a> {
type Item = &'a tt::TokenTree;
fn next(&mut self) -> Option<Self::Item> {
self.inner.next()
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.inner.size_hint()
}
}
impl<'a> std::iter::ExactSizeIterator for TtIter<'a> {}
|
