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use crate::ParseError;
use crate::subtree_parser::Parser;
#[derive(Clone)]
pub(crate) struct TtCursor<'a> {
subtree: &'a tt::Subtree,
pos: usize,
}
impl<'a> TtCursor<'a> {
pub(crate) fn new(subtree: &'a tt::Subtree) -> TtCursor<'a> {
TtCursor { subtree, pos: 0 }
}
pub(crate) fn is_eof(&self) -> bool {
self.pos == self.subtree.token_trees.len()
}
pub(crate) fn current(&self) -> Option<&'a tt::TokenTree> {
self.subtree.token_trees.get(self.pos)
}
pub(crate) fn at_punct(&self) -> Option<&'a tt::Punct> {
match self.current() {
Some(tt::TokenTree::Leaf(tt::Leaf::Punct(it))) => Some(it),
_ => None,
}
}
pub(crate) fn at_char(&self, char: char) -> bool {
match self.at_punct() {
Some(tt::Punct { char: c, .. }) if *c == char => true,
_ => false,
}
}
pub(crate) fn at_ident(&mut self) -> Option<&'a tt::Ident> {
match self.current() {
Some(tt::TokenTree::Leaf(tt::Leaf::Ident(i))) => Some(i),
_ => None,
}
}
pub(crate) fn bump(&mut self) {
self.pos += 1;
}
pub(crate) fn rev_bump(&mut self) {
self.pos -= 1;
}
pub(crate) fn eat(&mut self) -> Option<&'a tt::TokenTree> {
self.current().map(|it| {
self.bump();
it
})
}
pub(crate) fn eat_subtree(&mut self) -> Result<&'a tt::Subtree, ParseError> {
match self.current() {
Some(tt::TokenTree::Subtree(sub)) => {
self.bump();
Ok(sub)
}
_ => Err(ParseError::Expected(String::from("subtree"))),
}
}
pub(crate) fn eat_punct(&mut self) -> Option<&'a tt::Punct> {
self.at_punct().map(|it| {
self.bump();
it
})
}
pub(crate) fn eat_ident(&mut self) -> Option<&'a tt::Ident> {
self.at_ident().map(|i| {
self.bump();
i
})
}
pub(crate) fn eat_path(&mut self) -> Option<tt::TokenTree> {
let parser = Parser::new(&mut self.pos, self.subtree);
parser.parse_path()
}
pub(crate) fn expect_char(&mut self, char: char) -> Result<(), ParseError> {
if self.at_char(char) {
self.bump();
Ok(())
} else {
Err(ParseError::Expected(format!("`{}`", char)))
}
}
}
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