1 //! Parser recognizes special macro syntax, `$var` and `$(repeat)*`, in token
4 use smallvec::SmallVec;
7 use crate::{tt_iter::TtIter, MetaTemplate, ParseError};
9 #[derive(Clone, Debug, PartialEq, Eq)]
11 Var { name: SmolStr, kind: Option<SmolStr>, id: tt::TokenId },
12 Repeat { subtree: MetaTemplate, kind: RepeatKind, separator: Option<Separator> },
14 Subtree(MetaTemplate),
17 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
18 pub(crate) enum RepeatKind {
24 #[derive(Clone, Debug, Eq)]
25 pub(crate) enum Separator {
28 Puncts(SmallVec<[tt::Punct; 3]>),
31 // Note that when we compare a Separator, we just care about its textual value.
32 impl PartialEq for Separator {
33 fn eq(&self, other: &Separator) -> bool {
37 (Ident(ref a), Ident(ref b)) => a.text == b.text,
38 (Literal(ref a), Literal(ref b)) => a.text == b.text,
39 (Puncts(ref a), Puncts(ref b)) if a.len() == b.len() => {
40 let a_iter = a.iter().map(|a| a.char);
41 let b_iter = b.iter().map(|b| b.char);
49 pub(crate) fn parse_template(template: &tt::Subtree) -> Result<Vec<Op>, ParseError> {
50 parse_inner(&template, Mode::Template).into_iter().collect()
53 pub(crate) fn parse_pattern(pattern: &tt::Subtree) -> Result<Vec<Op>, ParseError> {
54 parse_inner(&pattern, Mode::Pattern).into_iter().collect()
57 #[derive(Clone, Copy)]
63 fn parse_inner(tt: &tt::Subtree, mode: Mode) -> Vec<Result<Op, ParseError>> {
64 let mut src = TtIter::new(&tt);
65 std::iter::from_fn(move || {
66 let first = src.next()?;
67 Some(next_op(first, &mut src, mode))
74 ParseError::UnexpectedToken(($($tt)*).to_string())
80 return Err(err!($($tt)*))
84 fn next_op<'a>(first: &tt::TokenTree, src: &mut TtIter<'a>, mode: Mode) -> Result<Op, ParseError> {
85 let res = match first {
86 tt::TokenTree::Leaf(leaf @ tt::Leaf::Punct(tt::Punct { char: '$', .. })) => {
87 // Note that the '$' itself is a valid token inside macro_rules.
88 let second = match src.next() {
89 None => return Ok(Op::Leaf(leaf.clone())),
93 tt::TokenTree::Subtree(subtree) => {
94 let (separator, kind) = parse_repeat(src)?;
95 let delimiter = subtree.delimiter;
96 let tokens = parse_inner(&subtree, mode)
98 .collect::<Result<Vec<Op>, ParseError>>()?;
99 let subtree = MetaTemplate { tokens, delimiter };
100 Op::Repeat { subtree, separator, kind }
102 tt::TokenTree::Leaf(leaf) => match leaf {
103 tt::Leaf::Punct(punct) => {
104 static UNDERSCORE: SmolStr = SmolStr::new_inline("_");
106 if punct.char != '_' {
107 return Err(ParseError::Expected("_".to_string()));
109 let name = UNDERSCORE.clone();
110 let kind = eat_fragment_kind(src, mode)?;
112 Op::Var { name, kind, id }
114 tt::Leaf::Ident(ident) if ident.text == "crate" => {
115 // We simply produce identifier `$crate` here. And it will be resolved when lowering ast to Path.
116 Op::Leaf(tt::Leaf::from(tt::Ident { text: "$crate".into(), id: ident.id }))
118 tt::Leaf::Ident(ident) => {
119 let name = ident.text.clone();
120 let kind = eat_fragment_kind(src, mode)?;
122 Op::Var { name, kind, id }
124 tt::Leaf::Literal(lit) => {
125 if is_boolean_literal(&lit) {
126 let name = lit.text.clone();
127 let kind = eat_fragment_kind(src, mode)?;
129 Op::Var { name, kind, id }
137 tt::TokenTree::Leaf(tt) => Op::Leaf(tt.clone()),
138 tt::TokenTree::Subtree(subtree) => {
139 let delimiter = subtree.delimiter;
141 parse_inner(&subtree, mode).into_iter().collect::<Result<Vec<Op>, ParseError>>()?;
143 let subtree = MetaTemplate { tokens, delimiter };
150 fn eat_fragment_kind<'a>(src: &mut TtIter<'a>, mode: Mode) -> Result<Option<SmolStr>, ParseError> {
151 if let Mode::Pattern = mode {
152 src.expect_char(':').map_err(|()| err!("bad fragment specifier 1"))?;
153 let ident = src.expect_ident().map_err(|()| err!("bad fragment specifier 1"))?;
154 return Ok(Some(ident.text.clone()));
159 fn is_boolean_literal(lit: &tt::Literal) -> bool {
160 matches!(lit.text.as_str(), "true" | "false")
163 fn parse_repeat(src: &mut TtIter) -> Result<(Option<Separator>, RepeatKind), ParseError> {
164 let mut separator = Separator::Puncts(SmallVec::new());
167 tt::TokenTree::Leaf(leaf) => leaf,
168 tt::TokenTree::Subtree(_) => return Err(ParseError::InvalidRepeat),
170 let has_sep = match &separator {
171 Separator::Puncts(puncts) => !puncts.is_empty(),
175 tt::Leaf::Ident(_) | tt::Leaf::Literal(_) if has_sep => {
176 return Err(ParseError::InvalidRepeat)
178 tt::Leaf::Ident(ident) => separator = Separator::Ident(ident.clone()),
179 tt::Leaf::Literal(lit) => separator = Separator::Literal(lit.clone()),
180 tt::Leaf::Punct(punct) => {
181 let repeat_kind = match punct.char {
182 '*' => RepeatKind::ZeroOrMore,
183 '+' => RepeatKind::OneOrMore,
184 '?' => RepeatKind::ZeroOrOne,
186 match &mut separator {
187 Separator::Puncts(puncts) => {
188 if puncts.len() == 3 {
189 return Err(ParseError::InvalidRepeat);
191 puncts.push(punct.clone())
193 _ => return Err(ParseError::InvalidRepeat),
198 let separator = if has_sep { Some(separator) } else { None };
199 return Ok((separator, repeat_kind));
203 Err(ParseError::InvalidRepeat)