| //! A "Parser" structure for token trees. We use this when parsing a declarative |
| //! macro definition into a list of patterns and templates. |
| |
| use smallvec::{smallvec, SmallVec}; |
| use syntax::SyntaxKind; |
| use tt::Span; |
| |
| use crate::{to_parser_input::to_parser_input, ExpandError, ExpandResult}; |
| |
| #[derive(Debug, Clone)] |
| pub(crate) struct TtIter<'a, S> { |
| pub(crate) inner: std::slice::Iter<'a, tt::TokenTree<S>>, |
| } |
| |
| impl<'a, S: Span> TtIter<'a, S> { |
| pub(crate) fn new(subtree: &'a tt::Subtree<S>) -> TtIter<'a, S> { |
| 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<S>, ()> { |
| match self.next() { |
| Some(tt::TokenTree::Subtree(it)) => Ok(it), |
| _ => Err(()), |
| } |
| } |
| |
| pub(crate) fn expect_leaf(&mut self) -> Result<&'a tt::Leaf<S>, ()> { |
| match self.next() { |
| Some(tt::TokenTree::Leaf(it)) => Ok(it), |
| _ => Err(()), |
| } |
| } |
| |
| pub(crate) fn expect_dollar(&mut self) -> Result<(), ()> { |
| match self.expect_leaf()? { |
| tt::Leaf::Punct(tt::Punct { char: '$', .. }) => Ok(()), |
| _ => Err(()), |
| } |
| } |
| |
| pub(crate) fn expect_ident(&mut self) -> Result<&'a tt::Ident<S>, ()> { |
| 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<S>, ()> { |
| match self.expect_leaf()? { |
| tt::Leaf::Ident(it) => Ok(it), |
| _ => Err(()), |
| } |
| } |
| |
| pub(crate) fn expect_literal(&mut self) -> Result<&'a tt::Leaf<S>, ()> { |
| 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_single_punct(&mut self) -> Result<&'a tt::Punct<S>, ()> { |
| match self.expect_leaf()? { |
| tt::Leaf::Punct(it) => Ok(it), |
| _ => Err(()), |
| } |
| } |
| |
| /// Returns consecutive `Punct`s that can be glued together. |
| /// |
| /// This method currently may return a single quotation, which is part of lifetime ident and |
| /// conceptually not a punct in the context of mbe. Callers should handle this. |
| pub(crate) fn expect_glued_punct(&mut self) -> Result<SmallVec<[tt::Punct<S>; 3]>, ()> { |
| let tt::TokenTree::Leaf(tt::Leaf::Punct(first)) = self.next().ok_or(())?.clone() else { |
| return Err(()); |
| }; |
| |
| if first.spacing == tt::Spacing::Alone { |
| return Ok(smallvec![first]); |
| } |
| |
| let (second, third) = match (self.peek_n(0), self.peek_n(1)) { |
| ( |
| Some(tt::TokenTree::Leaf(tt::Leaf::Punct(p2))), |
| Some(tt::TokenTree::Leaf(tt::Leaf::Punct(p3))), |
| ) if p2.spacing == tt::Spacing::Joint => (p2, Some(p3)), |
| (Some(tt::TokenTree::Leaf(tt::Leaf::Punct(p2))), _) => (p2, None), |
| _ => return Ok(smallvec![first]), |
| }; |
| |
| match (first.char, second.char, third.map(|it| it.char)) { |
| ('.', '.', Some('.' | '=')) | ('<', '<', Some('=')) | ('>', '>', Some('=')) => { |
| let _ = self.next().unwrap(); |
| let _ = self.next().unwrap(); |
| Ok(smallvec![first, *second, *third.unwrap()]) |
| } |
| ('-' | '!' | '*' | '/' | '&' | '%' | '^' | '+' | '<' | '=' | '>' | '|', '=', _) |
| | ('-' | '=' | '>', '>', _) |
| | ('<', '-', _) |
| | (':', ':', _) |
| | ('.', '.', _) |
| | ('&', '&', _) |
| | ('<', '<', _) |
| | ('|', '|', _) => { |
| let _ = self.next().unwrap(); |
| Ok(smallvec![first, *second]) |
| } |
| _ => Ok(smallvec![first]), |
| } |
| } |
| |
| pub(crate) fn expect_fragment( |
| &mut self, |
| entry_point: parser::PrefixEntryPoint, |
| ) -> ExpandResult<Option<tt::TokenTree<S>>> { |
| let buffer = tt::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::FloatSplit { .. } => { |
| // FIXME: We need to split the tree properly here, but mutating the token trees |
| // in the buffer is somewhat tricky to pull off. |
| 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![]; |
| |
| while curr != cursor { |
| let Some(token) = curr.token_tree() else { break }; |
| res.push(token.cloned()); |
| curr = curr.bump(); |
| } |
| |
| self.inner = self.inner.as_slice()[res.len()..].iter(); |
| let res = match &*res { |
| [] | [_] => res.pop(), |
| [first, ..] => Some(tt::TokenTree::Subtree(tt::Subtree { |
| delimiter: tt::Delimiter::invisible_spanned(first.first_span()), |
| token_trees: res.into_boxed_slice(), |
| })), |
| }; |
| ExpandResult { value: res, err } |
| } |
| |
| pub(crate) fn peek_n(&self, n: usize) -> Option<&'a tt::TokenTree<S>> { |
| self.inner.as_slice().get(n) |
| } |
| } |
| |
| impl<'a, S> Iterator for TtIter<'a, S> { |
| type Item = &'a tt::TokenTree<S>; |
| fn next(&mut self) -> Option<Self::Item> { |
| self.inner.next() |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.inner.size_hint() |
| } |
| } |
| |
| impl<S> std::iter::ExactSizeIterator for TtIter<'_, S> {} |