1 //! Parser recognizes special macro syntax, `$var` and `$(repeat)*`, in token
4 use smallvec::SmallVec;
8 use crate::{tt_iter::TtIter, ParseError};
10 #[derive(Clone, Debug, PartialEq, Eq)]
11 pub(crate) struct MetaTemplate(pub(crate) Vec<Op>);
13 #[derive(Debug, Clone, Copy)]
14 pub(crate) enum OpDelimited<'a> {
20 #[derive(Debug, Clone, Copy)]
21 pub(crate) struct OpDelimitedIter<'a> {
23 delimited: Option<&'a Delimiter>,
27 impl<'a> OpDelimitedIter<'a> {
28 pub(crate) fn is_eof(&self) -> bool {
29 let len = self.inner.len() + if self.delimited.is_some() { 2 } else { 0 };
33 pub(crate) fn peek(&self) -> Option<OpDelimited<'a>> {
34 match self.delimited {
35 None => self.inner.get(self.idx).map(OpDelimited::Op),
36 Some(_) => match self.idx {
37 0 => Some(OpDelimited::Open),
38 i if i == self.inner.len() + 1 => Some(OpDelimited::Close),
39 i => self.inner.get(i - 1).map(OpDelimited::Op),
44 pub(crate) fn reset(&self) -> Self {
45 Self { inner: &self.inner, idx: 0, delimited: self.delimited }
49 impl<'a> Iterator for OpDelimitedIter<'a> {
50 type Item = OpDelimited<'a>;
52 fn next(&mut self) -> Option<Self::Item> {
53 let res = self.peek();
58 fn size_hint(&self) -> (usize, Option<usize>) {
59 let len = self.inner.len() + if self.delimited.is_some() { 2 } else { 0 };
60 let remain = len.checked_sub(self.idx).unwrap_or(0);
61 (remain, Some(remain))
65 impl<'a> MetaTemplate {
66 pub(crate) fn iter(&self) -> impl Iterator<Item = &Op> {
70 pub(crate) fn iter_delimited(
72 delimited: Option<&'a Delimiter>,
73 ) -> OpDelimitedIter<'a> {
74 OpDelimitedIter { inner: &self.0, idx: 0, delimited }
78 #[derive(Clone, Debug, PartialEq, Eq)]
80 Var { name: SmolStr, kind: Option<SmolStr>, id: tt::TokenId },
81 Repeat { tokens: MetaTemplate, kind: RepeatKind, separator: Option<Separator> },
83 Subtree { tokens: MetaTemplate, delimiter: Option<Delimiter> },
86 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
87 pub(crate) enum RepeatKind {
93 #[derive(Clone, Debug, Eq)]
94 pub(crate) enum Separator {
97 Puncts(SmallVec<[tt::Punct; 3]>),
100 // Note that when we compare a Separator, we just care about its textual value.
101 impl PartialEq for Separator {
102 fn eq(&self, other: &Separator) -> bool {
105 match (self, other) {
106 (Ident(ref a), Ident(ref b)) => a.text == b.text,
107 (Literal(ref a), Literal(ref b)) => a.text == b.text,
108 (Puncts(ref a), Puncts(ref b)) if a.len() == b.len() => {
109 let a_iter = a.iter().map(|a| a.char);
110 let b_iter = b.iter().map(|b| b.char);
119 pub(crate) fn tt_count(&self) -> usize {
121 Separator::Literal(_) => 1,
122 Separator::Ident(_) => 1,
123 Separator::Puncts(it) => it.len(),
128 pub(crate) fn parse_template(template: &tt::Subtree) -> Result<Vec<Op>, ParseError> {
129 parse_inner(&template, Mode::Template).into_iter().collect()
132 pub(crate) fn parse_pattern(pattern: &tt::Subtree) -> Result<Vec<Op>, ParseError> {
133 parse_inner(&pattern, Mode::Pattern).into_iter().collect()
136 #[derive(Clone, Copy)]
142 fn parse_inner(tt: &tt::Subtree, mode: Mode) -> Vec<Result<Op, ParseError>> {
143 let mut src = TtIter::new(&tt);
144 std::iter::from_fn(move || {
145 let first = src.next()?;
146 Some(next_op(first, &mut src, mode))
153 ParseError::UnexpectedToken(($($tt)*).to_string())
159 return Err(err!($($tt)*))
163 fn next_op<'a>(first: &tt::TokenTree, src: &mut TtIter<'a>, mode: Mode) -> Result<Op, ParseError> {
164 let res = match first {
165 tt::TokenTree::Leaf(leaf @ tt::Leaf::Punct(tt::Punct { char: '$', .. })) => {
166 // Note that the '$' itself is a valid token inside macro_rules.
167 let second = match src.next() {
168 None => return Ok(Op::Leaf(leaf.clone())),
172 tt::TokenTree::Subtree(subtree) => {
173 let (separator, kind) = parse_repeat(src)?;
174 let tokens = parse_inner(&subtree, mode)
176 .collect::<Result<Vec<Op>, ParseError>>()?;
177 Op::Repeat { tokens: MetaTemplate(tokens), separator, kind }
179 tt::TokenTree::Leaf(leaf) => match leaf {
180 tt::Leaf::Punct(punct) => {
181 static UNDERSCORE: SmolStr = SmolStr::new_inline("_");
183 if punct.char != '_' {
184 return Err(ParseError::Expected("_".to_string()));
186 let name = UNDERSCORE.clone();
187 let kind = eat_fragment_kind(src, mode)?;
189 Op::Var { name, kind, id }
191 tt::Leaf::Ident(ident) if ident.text == "crate" => {
192 // We simply produce identifier `$crate` here. And it will be resolved when lowering ast to Path.
193 Op::Leaf(tt::Leaf::from(tt::Ident { text: "$crate".into(), id: ident.id }))
195 tt::Leaf::Ident(ident) => {
196 let name = ident.text.clone();
197 let kind = eat_fragment_kind(src, mode)?;
199 Op::Var { name, kind, id }
201 tt::Leaf::Literal(lit) => {
202 if is_boolean_literal(&lit) {
203 let name = lit.text.clone();
204 let kind = eat_fragment_kind(src, mode)?;
206 Op::Var { name, kind, id }
214 tt::TokenTree::Leaf(tt) => Op::Leaf(tt.clone()),
215 tt::TokenTree::Subtree(subtree) => {
217 parse_inner(&subtree, mode).into_iter().collect::<Result<Vec<Op>, ParseError>>()?;
218 Op::Subtree { tokens: MetaTemplate(tokens), delimiter: subtree.delimiter }
224 fn eat_fragment_kind<'a>(src: &mut TtIter<'a>, mode: Mode) -> Result<Option<SmolStr>, ParseError> {
225 if let Mode::Pattern = mode {
226 src.expect_char(':').map_err(|()| err!("bad fragment specifier 1"))?;
227 let ident = src.expect_ident().map_err(|()| err!("bad fragment specifier 1"))?;
228 return Ok(Some(ident.text.clone()));
233 fn is_boolean_literal(lit: &tt::Literal) -> bool {
234 matches!(lit.text.as_str(), "true" | "false")
237 fn parse_repeat(src: &mut TtIter) -> Result<(Option<Separator>, RepeatKind), ParseError> {
238 let mut separator = Separator::Puncts(SmallVec::new());
241 tt::TokenTree::Leaf(leaf) => leaf,
242 tt::TokenTree::Subtree(_) => return Err(ParseError::InvalidRepeat),
244 let has_sep = match &separator {
245 Separator::Puncts(puncts) => !puncts.is_empty(),
249 tt::Leaf::Ident(_) | tt::Leaf::Literal(_) if has_sep => {
250 return Err(ParseError::InvalidRepeat)
252 tt::Leaf::Ident(ident) => separator = Separator::Ident(ident.clone()),
253 tt::Leaf::Literal(lit) => separator = Separator::Literal(lit.clone()),
254 tt::Leaf::Punct(punct) => {
255 let repeat_kind = match punct.char {
256 '*' => RepeatKind::ZeroOrMore,
257 '+' => RepeatKind::OneOrMore,
258 '?' => RepeatKind::ZeroOrOne,
260 match &mut separator {
261 Separator::Puncts(puncts) => {
262 if puncts.len() == 3 {
263 return Err(ParseError::InvalidRepeat);
267 _ => return Err(ParseError::InvalidRepeat),
272 let separator = if has_sep { Some(separator) } else { None };
273 return Ok((separator, repeat_kind));
277 Err(ParseError::InvalidRepeat)