PR #30 Inline parser overhaul

Merge branch 'inline_perf'

Makefile

@@ -104,6 +104,6 @@ clean:
 	(cd tests/suite && make clean)
 	rm -f tests/bench/*.dj
 	(cd tests/bench && make clean)
-	rm -f bench/*.dj
+	find bench -type l -path 'bench/*.dj' -print0 | xargs -0 rm -f
 	rm -rf tests/afl/out
 	(cd examples/jotdown_wasm && make clean)

bench/inline-attrs.dj

@@ -0,0 +1,82 @@
+Inline{.a} attributes{#b} attached{c=d} to{.e} words{#f} probably{g=h}
+only{i=j} contain{.m} a{#n} single{o=pqrstuv} attribute{.wxyz} in{#å-ä-ö}
+the{абв=где} vast{.ёжз} majority{#ийк} of{мно=прс} cases{.туф}.
+
+However{.they #could potentially=contain .any #number of="attributes," .also
+#spanning multiple="lines," .even #the values="may span multiple lines
+like this,
+or even this"}. Attributes{.may}{#also}{be=concatenated}{.like}{#this}.
+
+[Attributes]{.abc} *may also*{ghi=jkl} _be attached to containers_{mno=pqr},
+{=they will most likely also contain a single attribute=}{.stu}.
+
+[{^Containers [_may *also*{.first}_{#second} be]{.third}^}{.fourth} nested]{#fifth}
+
+Attribute{values="can
+span
+any
+number
+of
+lines
+like
+a
+lot
+of
+lineee
+e
+ee
+e
+e
+e
+e
+s"
+%same
+with
+comments
+they
+can
+be
+lo
+o
+o
+o
+o
+ng%}
+
+Attribute{values="can
+span
+any
+number
+of
+lines
+like
+a
+lot
+of
+lineee
+e
+ee
+e
+e
+e
+e
+s"
+%even
+though
+they
+are
+long
+they
+could
+_*turn*_
+out
+to
+not
+be
+"attributes"
+at
+all
+in
+the
+end
+}

src/attr.rs

@@ -1,29 +1,34 @@
 use crate::CowStr;
-use crate::DiscontinuousString;
-use crate::Span;
-use std::borrow::Cow;
 use std::fmt;
 
-use State::*;
+/// Parse attributes, assumed to be valid.
-
+pub(crate) fn parse(src: &str) -> Attributes {
-pub(crate) fn parse<'s, S: DiscontinuousString<'s>>(chars: S) -> Attributes<'s> {
     let mut a = Attributes::new();
-    a.parse(chars);
+    a.parse(src);
     a
 }
 
 pub fn valid<I: Iterator<Item = char>>(chars: I) -> (usize, bool) {
+    use State::*;
+
     let mut has_attr = false;
-    let mut p = Parser::new(chars);
+    let mut n = 0;
-    for e in &mut p {
+    let mut state = Start;
-        match e {
+    for c in chars {
-            Element::Class(..) | Element::Identifier(..) | Element::Attribute(..) => {
+        n += 1;
-                has_attr = true;
+        state = state.step(c);
-            }
+        match state {
-            Element::Invalid => return (0, false),
+            Class | Identifier | Value | ValueQuoted => has_attr = true,
+            Done | Invalid => break,
+            _ => {}
         }
     }
-    (p.pos, has_attr)
+
+    if matches!(state, Done) {
+        (n, has_attr)
+    } else {
+        (0, false)
+    }
 }
 
 /// Stores an attribute value that supports backslash escapes of ASCII punctuation upon displaying,
@@ -39,6 +44,23 @@ impl<'s> AttributeValue<'s> {
     pub fn parts(&'s self) -> AttributeValueParts<'s> {
         AttributeValueParts { ahead: &self.raw }
     }
+
+    // lifetime is 's to avoid allocation if empty value is concatenated with single value
+    fn extend(&mut self, s: &'s str) {
+        match &mut self.raw {
+            CowStr::Borrowed(prev) => {
+                if prev.is_empty() {
+                    *prev = s;
+                } else {
+                    self.raw = format!("{} {}", prev, s).into();
+                }
+            }
+            CowStr::Owned(ref mut prev) => {
+                prev.push(' ');
+                prev.push_str(s);
+            }
+        }
+    }
 }
 
 impl<'s> From<&'s str> for AttributeValue<'s> {
@@ -113,24 +135,11 @@ impl<'s> Attributes<'s> {
         Self(self.0.take())
     }
 
-    pub(crate) fn parse<S: DiscontinuousString<'s>>(&mut self, input: S) -> bool {
+    /// Parse and append attributes, assumed to be valid.
-        #[inline]
+    pub(crate) fn parse(&mut self, input: &'s str) {
-        fn borrow(cow: CowStr) -> &str {
+        let mut parser = Parser::new(self.take());
-            match cow {
+        parser.parse(input);
-                Cow::Owned(_) => panic!(),
+        *self = parser.finish();
-                Cow::Borrowed(s) => s,
-            }
-        }
-
-        for elem in Parser::new(input.chars()) {
-            match elem {
-                Element::Class(c) => self.insert("class", input.src(c).into()),
-                Element::Identifier(i) => self.insert("id", input.src(i).into()),
-                Element::Attribute(a, v) => self.insert(borrow(input.src(a)), input.src(v).into()),
-                Element::Invalid => return false,
-            }
-        }
-        true
     }
 
     /// Combine all attributes from both objects, prioritizing self on conflicts.
@@ -152,6 +161,11 @@ impl<'s> Attributes<'s> {
     /// overwritten, unless it is a "class" attribute. In that case the provided value will be
     /// appended to the existing value.
     pub fn insert(&mut self, key: &'s str, val: AttributeValue<'s>) {
+        self.insert_pos(key, val);
+    }
+
+    // duplicate of insert but returns position of inserted value
+    fn insert_pos(&mut self, key: &'s str, val: AttributeValue<'s>) -> usize {
         if self.0.is_none() {
             self.0 = Some(Vec::new().into());
         };
@@ -160,12 +174,20 @@ impl<'s> Attributes<'s> {
         if let Some(i) = attrs.iter().position(|(k, _)| *k == key) {
             let prev = &mut attrs[i].1;
             if key == "class" {
-                *prev = format!("{} {}", prev, val).into();
+                match val.raw {
+                    CowStr::Borrowed(s) => prev.extend(s),
+                    CowStr::Owned(s) => {
+                        *prev = format!("{} {}", prev, s).into();
+                    }
+                }
             } else {
                 *prev = val;
             }
+            i
         } else {
+            let i = attrs.len();
             attrs.push((key, val));
+            i
         }
     }
 
@@ -217,6 +239,106 @@ impl<'s> std::fmt::Debug for Attributes<'s> {
     }
 }
 
+#[derive(Clone)]
+pub struct Validator {
+    state: State,
+}
+
+impl Validator {
+    pub fn new() -> Self {
+        Self {
+            state: State::Start,
+        }
+    }
+
+    pub fn restart(&mut self) {
+        self.state = State::Start;
+    }
+
+    /// Returns number of valid bytes parsed (0 means invalid) if finished, otherwise more input is
+    /// needed.
+    pub fn parse(&mut self, input: &str) -> Option<usize> {
+        let mut chars = input.chars();
+        for c in &mut chars {
+            self.state = self.state.step(c);
+            match self.state {
+                State::Done => return Some(input.len() - chars.as_str().len()),
+                State::Invalid => return Some(0),
+                _ => {}
+            }
+        }
+        None
+    }
+}
+
+/// Attributes parser, take input of one or more consecutive attributes and create an `Attributes`
+/// object.
+///
+/// Input is assumed to contain a valid series of attribute sets, the attributes are added as they
+/// are encountered.
+pub struct Parser<'s> {
+    attrs: Attributes<'s>,
+    i_prev: usize,
+    state: State,
+}
+
+impl<'s> Parser<'s> {
+    pub fn new(attrs: Attributes<'s>) -> Self {
+        Self {
+            attrs,
+            i_prev: usize::MAX,
+            state: State::Start,
+        }
+    }
+
+    /// Return value indicates the number of bytes parsed if finished. If None, more input is
+    /// required to finish the attributes.
+    pub fn parse(&mut self, input: &'s str) {
+        use State::*;
+
+        let mut pos = 0;
+        let mut pos_prev = 0;
+
+        for c in input.chars() {
+            let state_next = self.state.step(c);
+            let st = std::mem::replace(&mut self.state, state_next);
+
+            if st != self.state && !matches!((st, self.state), (ValueEscape, _) | (_, ValueEscape))
+            {
+                let content = &input[pos_prev..pos];
+                pos_prev = pos;
+                match st {
+                    Class => self.attrs.insert("class", content.into()),
+                    Identifier => self.attrs.insert("id", content.into()),
+                    Key => self.i_prev = self.attrs.insert_pos(content, "".into()),
+                    Value | ValueQuoted | ValueContinued => {
+                        self.attrs.0.as_mut().unwrap()[self.i_prev]
+                            .1
+                            .extend(&content[usize::from(matches!(st, ValueQuoted))..]);
+                    }
+                    _ => {}
+                }
+            };
+
+            pos += c.len_utf8();
+
+            debug_assert!(!matches!(self.state, Invalid));
+
+            if matches!(self.state, Done) {
+                if input[pos..].starts_with('{') {
+                    self.state = Start;
+                } else {
+                    return;
+                }
+            }
+        }
+    }
+
+    pub fn finish(self) -> Attributes<'s> {
+        self.attrs
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 enum State {
     Start,
@@ -226,190 +348,63 @@ enum State {
     Class,
     IdentifierFirst,
     Identifier,
-    Attribute,
+    Key,
     ValueFirst,
     Value,
     ValueQuoted,
+    ValueEscape,
+    ValueNewline,
+    ValueContinued,
     Done,
     Invalid,
 }
 
-struct Parser<I> {
+impl State {
-    chars: I,
+    fn step(self, c: char) -> State {
-    pos: usize,
+        use State::*;
-    pos_prev: usize,
-    state: State,
-}
 
-impl<I: Iterator<Item = char>> Parser<I> {
+        match self {
-    fn new(chars: I) -> Self {
+            Start if c == '{' => Whitespace,
-        Parser {
+            Start => Invalid,
-            chars,
-            pos: 0,
-            pos_prev: 0,
-            state: Start,
-        }
-    }
-
-    fn step_char(&mut self) -> Option<State> {
-        self.chars.next().map(|c| {
-            self.pos_prev = self.pos;
-            self.pos += c.len_utf8();
-            match self.state {
-                Start => match c {
-                    '{' => Whitespace,
-                    _ => Invalid,
-                },
             Whitespace => match c {
                 '}' => Done,
                 '.' => ClassFirst,
                 '#' => IdentifierFirst,
                 '%' => Comment,
-                    c if c.is_ascii_alphanumeric() || matches!(c, '_' | ':' | '-') => Attribute,
+                c if is_name(c) => Key,
                 c if c.is_whitespace() => Whitespace,
                 _ => Invalid,
             },
-                Comment => {
+            Comment if c == '%' => Whitespace,
-                    if c == '%' {
+            Comment => Comment,
-                        Whitespace
+            ClassFirst if is_name(c) => Class,
-                    } else {
+            ClassFirst => Invalid,
-                        Comment
+            IdentifierFirst if is_name(c) => Identifier,
+            IdentifierFirst => Invalid,
+            s @ (Class | Identifier | Value) if is_name(c) => s,
+            Class | Identifier | Value if c.is_whitespace() => Whitespace,
+            Class | Identifier | Value if c == '}' => Done,
+            Class | Identifier | Value => Invalid,
+            Key if is_name(c) => Key,
+            Key if c == '=' => ValueFirst,
+            Key => Invalid,
+            ValueFirst if is_name(c) => Value,
+            ValueFirst if c == '"' => ValueQuoted,
+            ValueFirst => Invalid,
+            ValueQuoted | ValueNewline | ValueContinued if c == '"' => Whitespace,
+            ValueQuoted | ValueNewline | ValueContinued | ValueEscape if c == '\n' => ValueNewline,
+            ValueQuoted if c == '\\' => ValueEscape,
+            ValueQuoted | ValueEscape => ValueQuoted,
+            ValueNewline | ValueContinued => ValueContinued,
+            Invalid | Done => panic!("{:?}", self),
         }
     }
-                s @ (ClassFirst | IdentifierFirst) => {
-                    if is_name(c) {
-                        match s {
-                            ClassFirst => Class,
-                            IdentifierFirst => Identifier,
-                            _ => panic!(),
-                        }
-                    } else {
-                        Invalid
-                    }
-                }
-                s @ (Class | Identifier | Value) => {
-                    if is_name(c) {
-                        s
-                    } else if c.is_whitespace() {
-                        Whitespace
-                    } else if c == '}' {
-                        Done
-                    } else {
-                        Invalid
-                    }
-                }
-                Attribute => {
-                    if is_name(c) {
-                        Attribute
-                    } else if c == '=' {
-                        ValueFirst
-                    } else {
-                        Invalid
-                    }
-                }
-                ValueFirst => {
-                    if is_name(c) {
-                        Value
-                    } else if c == '"' {
-                        ValueQuoted
-                    } else {
-                        Invalid
-                    }
-                }
-                ValueQuoted => match c {
-                    '\\' => {
-                        if let Some(c) = self.chars.next() {
-                            self.pos_prev = self.pos;
-                            self.pos += c.len_utf8();
-                        }
-                        ValueQuoted
-                    }
-                    '"' => Whitespace,
-                    _ => ValueQuoted,
-                },
-                Invalid | Done => panic!("{:?}", self.state),
-            }
-        })
-    }
-
-    fn step(&mut self) -> (State, Span) {
-        let start = self.pos_prev;
-
-        if self.state == Done {
-            return (Done, Span::empty_at(start));
-        }
-
-        if self.state == Invalid {
-            return (Invalid, Span::empty_at(start));
-        }
-
-        while let Some(state_next) = self.step_char() {
-            if self.state != state_next {
-                return (
-                    std::mem::replace(&mut self.state, state_next),
-                    Span::new(start, self.pos_prev),
-                );
-            }
-        }
-
-        (
-            if self.state == Done { Done } else { Invalid },
-            Span::new(start, self.pos_prev),
-        )
-    }
 }
 
 pub fn is_name(c: char) -> bool {
     c.is_ascii_alphanumeric() || matches!(c, ':' | '_' | '-')
 }
 
-enum Element {
-    Class(Span),
-    Identifier(Span),
-    Attribute(Span, Span),
-    Invalid,
-}
-
-impl<I: Iterator<Item = char>> Iterator for Parser<I> {
-    type Item = Element;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        loop {
-            let (st, span0) = self.step();
-            return match st {
-                ClassFirst | IdentifierFirst => {
-                    let (st, span1) = self.step();
-                    Some(match st {
-                        Class => Element::Class(span1),
-                        Identifier => Element::Identifier(span1),
-                        _ => return Some(Element::Invalid),
-                    })
-                }
-                Attribute => {
-                    let (st, _span1) = self.step();
-                    match st {
-                        ValueFirst => {
-                            let (st, span2) = self.step();
-                            match st {
-                                Value => Some(Element::Attribute(span0, span2)),
-                                ValueQuoted => Some(Element::Attribute(span0, span2.skip(1))),
-                                Invalid => Some(Element::Invalid),
-                                _ => panic!("{:?}", st),
-                            }
-                        }
-                        Invalid => Some(Element::Invalid),
-                        _ => panic!("{:?}", st),
-                    }
-                }
-                Comment | Start | Whitespace => continue,
-                Done => None,
-                Invalid => Some(Element::Invalid),
-                _ => panic!("{:?}", st),
-            };
-        }
-    }
-}
-
 #[cfg(test)]
 mod test {
     macro_rules! test_attr {
@@ -471,6 +466,11 @@ mod test {
         );
     }
 
+    #[test]
+    fn value_newline() {
+        test_attr!("{attr0=\"abc\ndef\"}", ("attr0", "abc def"));
+    }
+
     #[test]
     fn comment() {
         test_attr!("{%%}");

src/block.rs

@@ -215,7 +215,7 @@ impl<'s> TreeParser<'s> {
 
             // close list if a non list item or a list item of new type appeared
             if let Some(OpenList { ty, depth, .. }) = self.open_lists.last() {
-                assert!(usize::from(*depth) <= self.tree.depth());
+                debug_assert!(usize::from(*depth) <= self.tree.depth());
                 if self.tree.depth() == (*depth).into()
                     && !matches!(kind, Kind::ListItem { ty: ty_new, .. } if *ty == ty_new)
                 {
@@ -405,7 +405,7 @@ impl<'s> TreeParser<'s> {
         }
 
         if let Some(OpenList { depth, .. }) = self.open_lists.last() {
-            assert!(usize::from(*depth) <= self.tree.depth());
+            debug_assert!(usize::from(*depth) <= self.tree.depth());
             if self.tree.depth() == (*depth).into() {
                 self.prev_blankline = false;
                 self.prev_loose = false;
@@ -447,7 +447,7 @@ impl<'s> TreeParser<'s> {
                 .tree
                 .enter(Node::Container(TableRow { head: false }), row.with_len(1));
             let rem = row.skip(1); // |
-            let lex = lex::Lexer::new(rem.of(self.src).chars());
+            let lex = lex::Lexer::new(rem.of(self.src));
             let mut pos = rem.start();
             let mut cell_start = pos;
             let mut separator_row = true;

src/html.rs

@@ -96,7 +96,7 @@ impl Render for Renderer {
                     Container::DescriptionList => out.write_str("<dl")?,
                     Container::DescriptionDetails => out.write_str("<dd")?,
                     Container::Footnote { number, .. } => {
-                        assert!(self.footnote_number.is_none());
+                        debug_assert!(self.footnote_number.is_none());
                         self.footnote_number = Some((*number).try_into().unwrap());
                         if !self.encountered_footnote {
                             self.encountered_footnote = true;

src/lex.rs

@@ -13,7 +13,6 @@ pub(crate) struct Token {
 pub enum Kind {
     Text,
     Newline,
-    Whitespace,
     Nbsp,
     Hardbreak,
     Escape,
@@ -21,6 +20,7 @@ pub enum Kind {
     Close(Delimiter),
     Sym(Symbol),
     Seq(Sequence),
+    DollarBacktick(u8),
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -36,6 +36,7 @@ pub enum Delimiter {
     Bracket,
     BraceQuote1,
     BraceQuote2,
+    Paren,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -55,7 +56,6 @@ pub enum Symbol {
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Sequence {
     Backtick,
-    Dollar,
     Hyphen,
     Period,
 }
@@ -64,7 +64,6 @@ impl Sequence {
     fn ch(self) -> char {
         match self {
             Self::Backtick => '`',
-            Self::Dollar => '$',
             Self::Period => '.',
             Self::Hyphen => '-',
         }
@@ -72,9 +71,9 @@ impl Sequence {
 }
 
 #[derive(Clone)]
-pub(crate) struct Lexer<I: Iterator + Clone> {
+pub(crate) struct Lexer<'s> {
-    chars: I,
+    src: &'s str,
-    chars_non_peeked: I,
+    chars: std::str::Chars<'s>,
     /// Next character should be escaped.
     escape: bool,
     /// Token to be peeked or next'ed.
@@ -83,11 +82,11 @@ pub(crate) struct Lexer<I: Iterator + Clone> {
     len: usize,
 }
 
-impl<I: Iterator<Item = char> + Clone> Lexer<I> {
+impl<'s> Lexer<'s> {
-    pub fn new(chars: I) -> Lexer<I> {
+    pub fn new(src: &'s str) -> Self {
         Lexer {
-            chars: chars.clone(),
+            src,
-            chars_non_peeked: chars,
+            chars: src.chars(),
             escape: false,
             next: None,
             len: 0,
@@ -103,13 +102,14 @@ impl<I: Iterator<Item = char> + Clone> Lexer<I> {
         self.next.as_ref()
     }
 
-    pub fn chars(&self) -> I {
+    pub fn ahead(&self) -> &'s str {
-        self.chars_non_peeked.clone()
+        let pos =
+            self.src.len() - self.chars.as_str().len() - self.next.as_ref().map_or(0, |t| t.len);
+        &self.src[pos..]
     }
 
     fn next_token(&mut self) -> Option<Token> {
         let mut current = self.token();
-        self.chars_non_peeked = self.chars.clone();
 
         // concatenate text tokens
         if let Some(Token { kind: Text, len }) = &mut current {
@@ -148,7 +148,6 @@ impl<I: Iterator<Item = char> + Clone> Lexer<I> {
     }
 
     fn token(&mut self) -> Option<Token> {
-        self.chars_non_peeked = self.chars.clone();
         self.len = 0;
 
         let first = self.eat_char()?;
@@ -167,6 +166,8 @@ impl<I: Iterator<Item = char> + Clone> Lexer<I> {
             _ if escape && first == ' ' => Nbsp,
             _ if escape => Text,
 
+            '\n' => Newline,
+
             '\\' => {
                 if self
                     .peek_char()
@@ -179,14 +180,10 @@ impl<I: Iterator<Item = char> + Clone> Lexer<I> {
                 }
             }
 
-            '\n' => Newline,
-            _ if first.is_whitespace() => {
-                self.eat_while(char::is_whitespace);
-                Whitespace
-            }
-
             '[' => Open(Bracket),
             ']' => Close(Bracket),
+            '(' => Open(Paren),
+            ')' => Close(Paren),
             '{' => {
                 let explicit = match self.peek_char() {
                     Some('*') => Some(Open(BraceAsterisk)),
@@ -207,6 +204,7 @@ impl<I: Iterator<Item = char> + Clone> Lexer<I> {
                     Open(Brace)
                 }
             }
+            '}' => Close(Brace),
             '*' => self.maybe_eat_close_brace(Sym(Asterisk), BraceAsterisk),
             '^' => self.maybe_eat_close_brace(Sym(Caret), BraceCaret),
             '=' => self.maybe_eat_close_brace(Text, BraceEqual),
@@ -236,8 +234,21 @@ impl<I: Iterator<Item = char> + Clone> Lexer<I> {
             ':' => Sym(Colon),
 
             '`' => self.eat_seq(Backtick),
-            '$' => self.eat_seq(Dollar),
             '.' => self.eat_seq(Period),
+            '$' => {
+                self.eat_while(|c| c == '$');
+                let mut n_ticks: u8 = 0;
+                self.eat_while(|c| {
+                    if c == '`' {
+                        if let Some(l) = n_ticks.checked_add(1) {
+                            n_ticks = l;
+                            return true;
+                        }
+                    }
+                    false
+                });
+                DollarBacktick(n_ticks)
+            }
 
             _ => Text,
         };
@@ -267,17 +278,11 @@ impl<I: Iterator<Item = char> + Clone> Lexer<I> {
     }
 }
 
-impl<I: Iterator<Item = char> + Clone> Iterator for Lexer<I> {
+impl<'s> Iterator for Lexer<'s> {
     type Item = Token;
 
     fn next(&mut self) -> Option<Self::Item> {
-        self.next
+        self.next.take().or_else(|| self.next_token())
-            .take()
-            .map(|x| {
-                self.chars_non_peeked = self.chars.clone();
-                x
-            })
-            .or_else(|| self.next_token())
     }
 }
 
@@ -291,7 +296,7 @@ mod test {
     macro_rules! test_lex {
         ($($st:ident,)? $src:expr $(,$($token:expr),* $(,)?)?) => {
             #[allow(unused)]
-            let actual = super::Lexer::new($src.chars()).collect::<Vec<_>>();
+            let actual = super::Lexer::new($src).collect::<Vec<_>>();
             let expected = vec![$($($token),*,)?];
             assert_eq!(actual, expected, "{}", $src);
         };
@@ -313,18 +318,11 @@ mod test {
         test_lex!("abc", Text.l(3));
         test_lex!(
             "para w/ some _emphasis_ and *strong*.",
-            Text.l(4),
+            Text.l(13),
-            Whitespace.l(1),
-            Text.l(2),
-            Whitespace.l(1),
-            Text.l(4),
-            Whitespace.l(1),
             Sym(Underscore).l(1),
             Text.l(8),
             Sym(Underscore).l(1),
-            Whitespace.l(1),
+            Text.l(5),
-            Text.l(3),
-            Whitespace.l(1),
             Sym(Asterisk).l(1),
             Text.l(6),
             Sym(Asterisk).l(1),
@@ -383,11 +381,17 @@ mod test {
         test_lex!("`", Seq(Backtick).l(1));
         test_lex!("```", Seq(Backtick).l(3));
         test_lex!(
-            "`$-.",
+            "`-.",
             Seq(Backtick).l(1),
-            Seq(Dollar).l(1),
             Seq(Hyphen).l(1),
             Seq(Period).l(1),
         );
     }
+
+    #[test]
+    fn dollar_backtick() {
+        test_lex!("$`", DollarBacktick(1).l(2));
+        test_lex!("$$$`", DollarBacktick(1).l(4));
+        test_lex!("$$````", DollarBacktick(4).l(6));
+    }
 }

src/lib.rs

@@ -46,6 +46,8 @@
 //! # }
 //! ```
 
+#![allow(clippy::blocks_in_if_conditions)]
+
 use std::fmt;
 use std::fmt::Write as FmtWrite;
 use std::io;
@@ -60,7 +62,6 @@ mod lex;
 mod span;
 mod tree;
 
-use span::DiscontinuousString;
 use span::Span;
 
 pub use attr::{AttributeValue, AttributeValueParts, Attributes};
@@ -576,6 +577,9 @@ type Set<T> = std::collections::BTreeSet<T>;
 /// structure that will be kept for the duration of the parser's lifetime. Then, when the iterator
 /// is advanced, the parser will start from the beginning of the document and parse inline elements
 /// and emit [`Event`]s.
+///
+/// It is possible to clone the parser to e.g. avoid performing the block parsing multiple times.
+#[derive(Clone)]
 pub struct Parser<'s> {
     src: &'s str,
 
@@ -591,6 +595,9 @@ pub struct Parser<'s> {
     /// Current table row is a head row.
     table_head_row: bool,
 
+    /// Currently within a verbatim code block.
+    verbatim: bool,
+
     /// Footnote references in the order they were encountered, without duplicates.
     footnote_references: Vec<&'s str>,
     /// Cache of footnotes to emit at the end.
@@ -600,12 +607,11 @@ pub struct Parser<'s> {
     /// Currently within a footnote.
     footnote_active: bool,
 
-    /// Spans to the inlines in the leaf block currently being parsed.
+    /// Inline parser.
-    inlines: span::InlineSpans<'s>,
+    inline_parser: inline::Parser<'s>,
-    /// Inline parser, recreated for each new inline.
-    inline_parser: Option<inline::Parser<span::InlineCharsIter<'s>>>,
 }
 
+#[derive(Clone)]
 struct Heading {
     /// Location of heading in src.
     location: usize,
@@ -616,6 +622,7 @@ struct Heading {
 }
 
 /// Because of potential future references, an initial pass is required to obtain all definitions.
+#[derive(Clone)]
 struct PrePass<'s> {
     /// Link definitions and their attributes.
     link_definitions: Map<&'s str, (CowStr<'s>, attr::Attributes<'s>)>,
@@ -627,13 +634,11 @@ struct PrePass<'s> {
 
 impl<'s> PrePass<'s> {
     #[must_use]
-    fn new(src: &'s str, mut tree: block::Tree) -> Self {
+    fn new(src: &'s str, mut tree: block::Tree, inline_parser: &mut inline::Parser<'s>) -> Self {
         let mut link_definitions = Map::new();
         let mut headings: Vec<Heading> = Vec::new();
         let mut used_ids: Set<&str> = Set::new();
 
-        let mut inlines = span::InlineSpans::new(src);
-
         let mut attr_prev: Option<Span> = None;
         while let Some(e) = tree.next() {
             match e.kind {
@@ -662,12 +667,15 @@ impl<'s> PrePass<'s> {
                         .and_then(|attrs| attrs.get("id"))
                         .map(ToString::to_string);
 
-                    inlines.set_spans(tree.take_inlines());
                     let mut id_auto = String::new();
                     let mut last_whitespace = true;
-                    inline::Parser::new(inlines.chars()).for_each(|ev| match ev.kind {
+                    let inlines = tree.take_inlines().collect::<Vec<_>>();
+                    inline_parser.reset();
+                    inlines.iter().enumerate().for_each(|(i, sp)| {
+                        inline_parser.feed_line(*sp, i == inlines.len() - 1);
+                        inline_parser.for_each(|ev| match ev.kind {
                             inline::EventKind::Str => {
-                            let mut chars = inlines.slice(ev.span).chars().peekable();
+                                let mut chars = ev.span.of(src).chars().peekable();
                                 while let Some(c) = chars.next() {
                                     if c.is_whitespace() {
                                         while chars.peek().map_or(false, |c| c.is_whitespace()) {
@@ -687,6 +695,7 @@ impl<'s> PrePass<'s> {
                                 id_auto.push('-');
                             }
                             _ => {}
+                        })
                     });
                     id_auto.drain(id_auto.trim_end_matches('-').len()..);
 
@@ -765,7 +774,8 @@ impl<'s> Parser<'s> {
     #[must_use]
     pub fn new(src: &'s str) -> Self {
         let tree = block::parse(src);
-        let pre_pass = PrePass::new(src, tree.clone());
+        let mut inline_parser = inline::Parser::new(src);
+        let pre_pass = PrePass::new(src, tree.clone(), &mut inline_parser);
 
         Self {
             src,
@@ -773,34 +783,32 @@ impl<'s> Parser<'s> {
             pre_pass,
             block_attributes: Attributes::new(),
             table_head_row: false,
+            verbatim: false,
             footnote_references: Vec::new(),
             footnotes: Map::new(),
             footnote_index: 0,
             footnote_active: false,
-            inlines: span::InlineSpans::new(src),
+            inline_parser,
-            inline_parser: None,
         }
     }
 
     fn inline(&mut self) -> Option<Event<'s>> {
-        self.inline_parser.as_mut().and_then(|parser| {
+        let next = self.inline_parser.next()?;
-            let mut inline = parser.next();
 
-            let mut first_is_attr = false;
+        let (inline, mut attributes) = match next {
-            let mut attributes = inline.as_ref().map_or_else(Attributes::new, |inl| {
+            inline::Event {
-                if let inline::EventKind::Attributes = inl.kind {
+                kind: inline::EventKind::Attributes { attrs, .. },
-                    first_is_attr = true;
+                ..
-                    attr::parse(self.inlines.slice(inl.span))
+            } => (
-                } else {
+                self.inline_parser.next(),
-                    Attributes::new()
+                self.inline_parser.store_attributes[attrs as usize].clone(),
-                }
+            ),
-            });
+            inline => (Some(inline), Attributes::new()),
+        };
 
-            if first_is_attr {
+        inline.map(|inline| {
-                inline = parser.next();
+            let enter = matches!(inline.kind, inline::EventKind::Enter(_));
-            }
+            match inline.kind {
-
-            inline.map(|inline| match inline.kind {
                 inline::EventKind::Enter(c) | inline::EventKind::Exit(c) => {
                     let t = match c {
                         inline::Container::Span => Container::Span,
@@ -808,10 +816,7 @@ impl<'s> Parser<'s> {
                         inline::Container::InlineMath => Container::Math { display: false },
                         inline::Container::DisplayMath => Container::Math { display: true },
                         inline::Container::RawFormat => Container::RawInline {
-                            format: match self.inlines.src(inline.span) {
+                            format: inline.span.of(self.src),
-                                CowStr::Owned(_) => panic!(),
-                                CowStr::Borrowed(s) => s,
-                            },
                         },
                         inline::Container::Subscript => Container::Subscript,
                         inline::Container::Superscript => Container::Superscript,
@@ -820,46 +825,41 @@ impl<'s> Parser<'s> {
                         inline::Container::Emphasis => Container::Emphasis,
                         inline::Container::Strong => Container::Strong,
                         inline::Container::Mark => Container::Mark,
-                        inline::Container::InlineLink => Container::Link(
+                        inline::Container::InlineLink(url) => Container::Link(
-                            match self.inlines.src(inline.span) {
+                            self.inline_parser.store_cowstrs[url as usize].clone(),
-                                CowStr::Owned(s) => s.replace('\n', "").into(),
-                                s @ CowStr::Borrowed(_) => s,
-                            },
                             LinkType::Span(SpanLinkType::Inline),
                         ),
-                        inline::Container::InlineImage => Container::Image(
+                        inline::Container::InlineImage(url) => Container::Image(
-                            match self.inlines.src(inline.span) {
+                            self.inline_parser.store_cowstrs[url as usize].clone(),
-                                CowStr::Owned(s) => s.replace('\n', "").into(),
-                                s @ CowStr::Borrowed(_) => s,
-                            },
                             SpanLinkType::Inline,
                         ),
-                        inline::Container::ReferenceLink | inline::Container::ReferenceImage => {
+                        inline::Container::ReferenceLink(tag)
-                            let tag = match self.inlines.src(inline.span) {
+                        | inline::Container::ReferenceImage(tag) => {
-                                CowStr::Owned(s) => s.replace('\n', " ").into(),
+                            let tag = &self.inline_parser.store_cowstrs[tag as usize];
-                                s @ CowStr::Borrowed(_) => s,
+                            let link_def = self
-                            };
+                                .pre_pass
-                            let link_def =
+                                .link_definitions
-                                self.pre_pass.link_definitions.get(tag.as_ref()).cloned();
+                                .get::<str>(tag.as_ref())
+                                .cloned();
 
                             let (url_or_tag, ty) = if let Some((url, attrs_def)) = link_def {
                                 attributes.union(attrs_def);
                                 (url, SpanLinkType::Reference)
                             } else {
                                 self.pre_pass.heading_id_by_tag(tag.as_ref()).map_or_else(
-                                    || (tag, SpanLinkType::Unresolved),
+                                    || (tag.clone(), SpanLinkType::Unresolved),
                                     |id| (format!("#{}", id).into(), SpanLinkType::Reference),
                                 )
                             };
 
-                            if matches!(c, inline::Container::ReferenceLink) {
+                            if matches!(c, inline::Container::ReferenceLink(..)) {
                                 Container::Link(url_or_tag, LinkType::Span(ty))
                             } else {
                                 Container::Image(url_or_tag, ty)
                             }
                         }
                         inline::Container::Autolink => {
-                            let url = self.inlines.src(inline.span);
+                            let url: CowStr = inline.span.of(self.src).into();
                             let ty = if url.contains('@') {
                                 LinkType::Email
                             } else {
@@ -868,7 +868,7 @@ impl<'s> Parser<'s> {
                             Container::Link(url, ty)
                         }
                     };
-                    if matches!(inline.kind, inline::EventKind::Enter(_)) {
+                    if enter {
                         Event::Start(t, attributes)
                     } else {
                         Event::End(t)
@@ -876,10 +876,7 @@ impl<'s> Parser<'s> {
                 }
                 inline::EventKind::Atom(a) => match a {
                     inline::Atom::FootnoteReference => {
-                        let tag = match self.inlines.src(inline.span) {
+                        let tag = inline.span.of(self.src);
-                            CowStr::Borrowed(s) => s,
-                            CowStr::Owned(..) => panic!(),
-                        };
                         let number = self
                             .footnote_references
                             .iter()
@@ -891,15 +888,9 @@ impl<'s> Parser<'s> {
                                 },
                                 |i| i + 1,
                             );
-                        Event::FootnoteReference(
+                        Event::FootnoteReference(inline.span.of(self.src), number)
-                            match self.inlines.src(inline.span) {
-                                CowStr::Borrowed(s) => s,
-                                CowStr::Owned(..) => panic!(),
-                            },
-                            number,
-                        )
                     }
-                    inline::Atom::Symbol => Event::Symbol(self.inlines.src(inline.span)),
+                    inline::Atom::Symbol => Event::Symbol(inline.span.of(self.src).into()),
                     inline::Atom::Quote { ty, left } => match (ty, left) {
                         (inline::QuoteType::Single, true) => Event::LeftSingleQuote,
                         (inline::QuoteType::Single, false) => Event::RightSingleQuote,
@@ -914,13 +905,11 @@ impl<'s> Parser<'s> {
                     inline::Atom::Hardbreak => Event::Hardbreak,
                     inline::Atom::Escape => Event::Escape,
                 },
-                inline::EventKind::Str => Event::Str(self.inlines.src(inline.span)),
+                inline::EventKind::Str => Event::Str(inline.span.of(self.src).into()),
-                inline::EventKind::Whitespace
+                inline::EventKind::Attributes { .. } | inline::EventKind::Placeholder => {
-                | inline::EventKind::Attributes
-                | inline::EventKind::Placeholder => {
                     panic!("{:?}", inline)
                 }
-            })
+            }
         })
     }
 
@@ -942,6 +931,7 @@ impl<'s> Parser<'s> {
                     let enter = matches!(ev.kind, tree::EventKind::Enter(..));
                     let cont = match c {
                         block::Node::Leaf(l) => {
+                            self.inline_parser.reset();
                             if matches!(l, block::Leaf::LinkDefinition) {
                                 // ignore link definitions
                                 if enter {
@@ -950,11 +940,6 @@ impl<'s> Parser<'s> {
                                 self.block_attributes = Attributes::new();
                                 continue;
                             }
-                            if enter && !matches!(l, block::Leaf::CodeBlock) {
-                                self.inlines.set_spans(self.tree.take_inlines());
-                                self.inline_parser =
-                                    Some(inline::Parser::new(self.inlines.chars()));
-                            }
                             match l {
                                 block::Leaf::Paragraph => Container::Paragraph,
                                 block::Leaf::Heading { has_section } => Container::Heading {
@@ -969,6 +954,7 @@ impl<'s> Parser<'s> {
                                 },
                                 block::Leaf::DescriptionTerm => Container::DescriptionTerm,
                                 block::Leaf::CodeBlock => {
+                                    self.verbatim = enter;
                                     if let Some(format) = content.strip_prefix('=') {
                                         Container::RawBlock { format }
                                     } else {
@@ -991,7 +977,7 @@ impl<'s> Parser<'s> {
                                 class: (!ev.span.is_empty()).then(|| content),
                             },
                             block::Container::Footnote => {
-                                assert!(enter);
+                                debug_assert!(enter);
                                 self.footnotes.insert(content, self.tree.take_branch());
                                 self.block_attributes = Attributes::new();
                                 continue;
@@ -1048,7 +1034,15 @@ impl<'s> Parser<'s> {
                         Event::End(cont)
                     }
                 }
-                tree::EventKind::Inline => Event::Str(content.into()), // verbatim
+                tree::EventKind::Inline => {
+                    if self.verbatim {
+                        Event::Str(content.into())
+                    } else {
+                        self.inline_parser
+                            .feed_line(ev.span, self.tree.branch_is_empty());
+                        return self.next();
+                    }
+                }
             };
             return Some(event);
         }
@@ -1304,7 +1298,8 @@ mod test {
             Start(Blockquote, Attributes::new()),
             Start(Paragraph, Attributes::new()),
             Start(Verbatim, Attributes::new()),
-            Str("abc\ndef".into()),
+            Str("abc\n".into()),
+            Str("def".into()),
             End(Verbatim),
             End(Paragraph),
             End(Blockquote),
@@ -1358,6 +1353,10 @@ mod test {
             End(Link("url".into(), LinkType::Span(SpanLinkType::Inline))),
             End(Paragraph),
         );
+    }
+
+    #[test]
+    fn link_inline_multi_line() {
         test_parse!(
             concat!(
                 "> [text](url\n",
@@ -1374,6 +1373,23 @@ mod test {
             End(Paragraph),
             End(Blockquote),
         );
+        test_parse!(
+            concat!(
+                "> [text](a\n", //
+                "> bc\n",       //
+                "> def)\n",     //
+            ),
+            Start(Blockquote, Attributes::new()),
+            Start(Paragraph, Attributes::new()),
+            Start(
+                Link("abcdef".into(), LinkType::Span(SpanLinkType::Inline)),
+                Attributes::new()
+            ),
+            Str("text".into()),
+            End(Link("abcdef".into(), LinkType::Span(SpanLinkType::Inline))),
+            End(Paragraph),
+            End(Blockquote),
+        );
     }
 
     #[test]
@@ -1440,6 +1456,29 @@ mod test {
 
     #[test]
     fn link_reference_multiline() {
+        test_parse!(
+            concat!(
+                "> [text][a\n", //
+                "> b]\n",       //
+                "\n",           //
+                "[a b]: url\n", //
+            ),
+            Start(Blockquote, Attributes::new()),
+            Start(Paragraph, Attributes::new()),
+            Start(
+                Link("url".into(), LinkType::Span(SpanLinkType::Reference)),
+                Attributes::new()
+            ),
+            Str("text".into()),
+            End(Link("url".into(), LinkType::Span(SpanLinkType::Reference))),
+            End(Paragraph),
+            End(Blockquote),
+            Blankline,
+        );
+    }
+
+    #[test]
+    fn link_definition_multiline() {
         test_parse!(
             concat!(
                 "[text][tag]\n",
@@ -1662,6 +1701,165 @@ mod test {
         );
     }
 
+    #[test]
+    fn attr_inline_consecutive() {
+        test_parse!(
+            "_abc def_{.a}{.b #i}",
+            Start(Paragraph, Attributes::new()),
+            Start(
+                Emphasis,
+                [("class", "a b"), ("id", "i")].into_iter().collect(),
+            ),
+            Str("abc def".into()),
+            End(Emphasis),
+            End(Paragraph),
+        );
+        test_parse!(
+            "_abc def_{.a}{%%}{.b #i}",
+            Start(Paragraph, Attributes::new()),
+            Start(
+                Emphasis,
+                [("class", "a b"), ("id", "i")].into_iter().collect(),
+            ),
+            Str("abc def".into()),
+            End(Emphasis),
+            End(Paragraph),
+        );
+    }
+
+    #[test]
+    fn attr_inline_consecutive_invalid() {
+        test_parse!(
+            "_abc def_{.a}{.b #i}{.c invalid}",
+            Start(Paragraph, Attributes::new()),
+            Start(
+                Emphasis,
+                [("class", "a b"), ("id", "i")].into_iter().collect(),
+            ),
+            Str("abc def".into()),
+            End(Emphasis),
+            Str("{.c invalid}".into()),
+            End(Paragraph),
+        );
+        test_parse!(
+            "_abc def_{.a}{.b #i}{%%}{.c invalid}",
+            Start(Paragraph, Attributes::new()),
+            Start(
+                Emphasis,
+                [("class", "a b"), ("id", "i")].into_iter().collect(),
+            ),
+            Str("abc def".into()),
+            End(Emphasis),
+            Str("{.c invalid}".into()),
+            End(Paragraph),
+        );
+        test_parse!(
+            concat!("_abc def_{.a}{.b #i}{%%}{.c\n", "invalid}\n"),
+            Start(Paragraph, Attributes::new()),
+            Start(
+                Emphasis,
+                [("class", "a b"), ("id", "i")].into_iter().collect(),
+            ),
+            Str("abc def".into()),
+            End(Emphasis),
+            Str("{.c".into()),
+            Softbreak,
+            Str("invalid}".into()),
+            End(Paragraph),
+        );
+    }
+
+    #[test]
+    fn attr_inline_multiline() {
+        test_parse!(
+            concat!(
+                "> _abc_{a=b\n", //
+                "> c=d}\n",      //
+            ),
+            Start(Blockquote, Attributes::new()),
+            Start(Paragraph, Attributes::new()),
+            Start(Emphasis, [("a", "b"), ("c", "d")].into_iter().collect()),
+            Str("abc".into()),
+            End(Emphasis),
+            End(Paragraph),
+            End(Blockquote),
+        );
+        test_parse!(
+            concat!(
+                "> a{\n",   //
+                "> %%\n",   //
+                "> a=a}\n", //
+            ),
+            Start(Blockquote, Attributes::new()),
+            Start(Paragraph, Attributes::new()),
+            Start(Span, [("a", "a")].into_iter().collect()),
+            Str("a".into()),
+            End(Span),
+            End(Paragraph),
+            End(Blockquote),
+        );
+        test_parse!(
+            concat!(
+                "> a{a=\"a\n", //
+                "> b\n",       //
+                "> c\"}\n",    //
+            ),
+            Start(Blockquote, Attributes::new()),
+            Start(Paragraph, Attributes::new()),
+            Start(Span, [("a", "a b c")].into_iter().collect()),
+            Str("a".into()),
+            End(Span),
+            End(Paragraph),
+            End(Blockquote),
+        );
+        test_parse!(
+            concat!(
+                "> a{a=\"\n", //
+                "> b\"}\n",   //
+            ),
+            Start(Blockquote, Attributes::new()),
+            Start(Paragraph, Attributes::new()),
+            Start(Span, [("a", "b")].into_iter().collect()),
+            Str("a".into()),
+            End(Span),
+            End(Paragraph),
+            End(Blockquote),
+        );
+    }
+
+    #[test]
+    fn attr_inline_multiline_unclosed() {
+        test_parse!(
+            concat!(
+                "a{\n", //
+                " b\n", //
+            ),
+            Start(Paragraph, Attributes::new()),
+            Str("a{".into()),
+            Softbreak,
+            Str("b".into()),
+            End(Paragraph),
+        );
+    }
+
+    #[test]
+    fn attr_inline_multiline_invalid() {
+        test_parse!(
+            concat!(
+                "a{a=b\n", //
+                " b\n",    //
+                "}",       //
+            ),
+            Start(Paragraph, Attributes::new()),
+            Str("a{a=b".into()),
+            Softbreak,
+            Str("b".into()),
+            Softbreak,
+            Str("}".into()),
+            End(Paragraph),
+        );
+    }
+
     #[test]
     fn list_item_unordered() {
         test_parse!(

src/span.rs

@@ -1,5 +1,3 @@
-use crate::CowStr;
-
 #[derive(Clone, Copy, Default, Debug, PartialEq, Eq)]
 pub struct Span {
     start: u32,
@@ -30,14 +28,6 @@ impl Span {
         Self::empty_at(self.end())
     }
 
-    pub fn with_start(self, start: usize) -> Self {
-        Self::new(start, self.end())
-    }
-
-    pub fn with_end(self, end: usize) -> Self {
-        Self::new(self.start(), end)
-    }
-
     pub fn with_len(self, len: usize) -> Self {
         Self::by_len(self.start(), len)
     }
@@ -115,205 +105,6 @@ impl Span {
     }
 }
 
-pub trait DiscontinuousString<'s> {
-    type Chars: Iterator<Item = char>;
-
-    fn src(&self, span: Span) -> CowStr<'s>;
-
-    fn chars(&self) -> Self::Chars;
-}
-
-impl<'s> DiscontinuousString<'s> for &'s str {
-    type Chars = std::str::Chars<'s>;
-
-    fn src(&self, span: Span) -> CowStr<'s> {
-        span.of(self).into()
-    }
-
-    fn chars(&self) -> Self::Chars {
-        str::chars(self)
-    }
-}
-
-/// Multiple discontinuous [`std::str::Chars`] objects concatenated.
-#[derive(Clone)]
-pub struct InlineChars<'s, I> {
-    src: &'s str,
-    inlines: I,
-    next: std::str::Chars<'s>,
-}
-
-// Implement inlines.flat_map(|sp| sp.of(self.src).chars())
-impl<'s, I: Iterator<Item = Span>> InlineChars<'s, I> {
-    fn new(src: &'s str, inlines: I) -> Self {
-        Self {
-            src,
-            inlines,
-            next: "".chars(),
-        }
-    }
-}
-
-impl<'s, I: Iterator<Item = Span>> Iterator for InlineChars<'s, I> {
-    type Item = char;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if self.next.as_str().is_empty() {
-            self.next = self
-                .inlines
-                .next()
-                .map_or_else(|| "".chars(), |sp| sp.of(self.src).chars());
-        }
-        self.next.next()
-    }
-}
-
-pub type InlineCharsIter<'s> = InlineChars<'s, std::iter::Copied<std::slice::Iter<'static, Span>>>;
-
-/// Discontinuous slices of a [`&str`].
-#[derive(Default, Debug)]
-pub struct InlineSpans<'s> {
-    src: &'s str,
-    spans: Vec<Span>,
-}
-
-impl<'s> InlineSpans<'s> {
-    pub fn new(src: &'s str) -> Self {
-        Self {
-            src,
-            spans: Vec::new(),
-        }
-    }
-
-    pub fn set_spans(&mut self, spans: impl Iterator<Item = Span>) {
-        self.spans.clear();
-        self.spans.extend(spans);
-    }
-
-    pub fn slice<'i>(&'i self, span: Span) -> InlineSpansSlice<'s, 'i> {
-        let mut first = 0;
-        let mut last = 0;
-        let mut first_skip = 0;
-        let mut last_len = 0;
-
-        let mut a = 0;
-        for (i, sp) in self.spans.iter().enumerate() {
-            let b = a + sp.len();
-            if span.start() < b {
-                if a <= span.start() {
-                    first = i;
-                    first_skip = span.start() - a;
-                    if span.end() <= b {
-                        // continuous
-                        last = i;
-                        last_len = span.len();
-                        break;
-                    }
-                } else {
-                    last = i;
-                    last_len = sp.len().min(span.end() - a);
-                    break;
-                };
-            }
-            a = b;
-        }
-
-        assert_ne!(last_len, 0);
-
-        InlineSpansSlice {
-            src: self.src,
-            first_skip,
-            last_len,
-            spans: &self.spans[first..=last],
-        }
-    }
-
-    /// Borrow if continuous, copy if discontiunous.
-    fn borrow_or_copy<I: Iterator<Item = Span>>(src: &str, spans: I, span: Span) -> CowStr {
-        let mut a = 0;
-        let mut s = String::new();
-        for sp in spans {
-            let b = a + sp.len();
-            if span.start() < b {
-                let r = if a <= span.start() {
-                    if span.end() <= b {
-                        // continuous
-                        return CowStr::Borrowed(&sp.of(src)[span.start() - a..span.end() - a]);
-                    }
-                    (span.start() - a)..sp.len()
-                } else if a <= span.end() {
-                    0..sp.len().min(span.end() - a)
-                } else {
-                    break;
-                };
-                s.push_str(&sp.of(src)[r]);
-            }
-            a = b;
-        }
-        assert_eq!(span.len(), s.len());
-        CowStr::Owned(s)
-    }
-}
-
-impl<'s> DiscontinuousString<'s> for InlineSpans<'s> {
-    type Chars = InlineCharsIter<'s>;
-
-    fn src(&self, span: Span) -> CowStr<'s> {
-        Self::borrow_or_copy(self.src, self.spans.iter().copied(), span)
-    }
-
-    fn chars(&self) -> Self::Chars {
-        // SAFETY: do not call set_spans while chars is in use
-        unsafe { std::mem::transmute(InlineChars::new(self.src, self.spans.iter().copied())) }
-    }
-}
-
-/// A read-only slice of an [`InlineSpans`] object.
-pub struct InlineSpansSlice<'s, 'i> {
-    src: &'s str,
-    first_skip: usize,
-    last_len: usize,
-    spans: &'i [Span],
-}
-
-impl<'s, 'i> InlineSpansSlice<'s, 'i> {
-    fn spans(&self) -> InlineSpansSliceIter<'i> {
-        let (span_start, r_middle, span_end) = if self.spans.len() == 1 {
-            (
-                Span::by_len(self.spans[0].start() + self.first_skip, self.last_len),
-                0..0,
-                Span::by_len(self.spans[self.spans.len() - 1].start(), 0),
-            )
-        } else {
-            (
-                Span::new(self.spans[0].start() + self.first_skip, self.spans[0].end()),
-                1..1 + self.spans.len().saturating_sub(2),
-                Span::by_len(self.spans[self.spans.len() - 1].start(), self.last_len),
-            )
-        };
-        std::iter::once(span_start)
-            .chain(self.spans[r_middle].iter().copied())
-            .chain(std::iter::once(span_end))
-    }
-}
-
-impl<'s, 'i> DiscontinuousString<'s> for InlineSpansSlice<'s, 'i> {
-    type Chars = InlineChars<'s, InlineSpansSliceIter<'i>>;
-
-    fn src(&self, span: Span) -> CowStr<'s> {
-        InlineSpans::borrow_or_copy(self.src, self.spans(), span)
-    }
-
-    fn chars(&self) -> Self::Chars {
-        InlineChars::new(self.src, self.spans())
-    }
-}
-
-pub type InlineSpansSliceIter<'i> = std::iter::Chain<
-    std::iter::Chain<std::iter::Once<Span>, std::iter::Copied<std::slice::Iter<'i, Span>>>,
-    std::iter::Once<Span>,
->;
-
 #[cfg(test)]
 mod test {
     use super::Span;

src/tree.rs

@@ -79,12 +79,16 @@ impl<C: Clone, A: Clone> Tree<C, A> {
         std::iter::from_fn(move || {
             head.take().map(|h| {
                 let n = &self.nodes[h.index()];
-                assert!(matches!(n.kind, NodeKind::Inline));
+                debug_assert!(matches!(n.kind, NodeKind::Inline));
                 head = n.next;
                 n.span
             })
         })
     }
+
+    pub fn branch_is_empty(&self) -> bool {
+        matches!(self.head, None)
+    }
 }
 
 impl<C: Clone, A: Clone> Iterator for Tree<C, A> {
@@ -126,7 +130,7 @@ pub struct NodeIndex(std::num::NonZeroUsize);
 
 impl NodeIndex {
     fn new(i: usize) -> Self {
-        assert_ne!(i, usize::MAX);
+        debug_assert_ne!(i, usize::MAX);
         Self((i + 1).try_into().unwrap())
     }
 
@@ -246,7 +250,7 @@ impl<C, A> Builder<C, A> {
             }
         } else {
             let last = self.branch.pop();
-            assert_ne!(last, None);
+            debug_assert_ne!(last, None);
         }
     }
 
@@ -314,7 +318,7 @@ impl<C, A> Builder<C, A> {
     }
 
     pub(super) fn finish(self) -> Tree<C, A> {
-        assert_eq!(self.depth, 0);
+        debug_assert_eq!(self.depth, 0);
         let head = self.nodes[NodeIndex::root().index()].next;
         Tree {
             nodes: self.nodes.into_boxed_slice().into(),
@@ -331,19 +335,19 @@ impl<C, A> Builder<C, A> {
             match &mut head.kind {
                 NodeKind::Root | NodeKind::Inline | NodeKind::Atom(_) => {
                     // set next pointer of previous node
-                    assert_eq!(head.next, None);
+                    debug_assert_eq!(head.next, None);
                     head.next = Some(ni);
                 }
                 NodeKind::Container(_, child) => {
                     self.branch.push(*head_ni);
                     // set child pointer of current container
-                    assert_eq!(*child, None);
+                    debug_assert_eq!(*child, None);
                     *child = Some(ni);
                 }
             }
         } else if let Some(block) = self.branch.pop() {
             let mut block = &mut self.nodes[block.index()];
-            assert!(matches!(block.kind, NodeKind::Container(..)));
+            debug_assert!(matches!(block.kind, NodeKind::Container(..)));
             block.next = Some(ni);
         } else {
             panic!()

tests/suite/skip

@@ -1,6 +1,5 @@
 38d85f9:multi-line block attributes
 6c14561:multi-line block attributes
-613a9d6:attribute container precedence
 f4f22fc:attribute key class order
 ae6fc15:bugged left/right quote
 168469a:bugged left/right quote
@@ -9,9 +8,7 @@ ae6fc15:bugged left/right quote
 e1f5b5e:untrimmed whitespace before linebreak
 07888f3:div close within raw block
 8423412:heading id conflict with existing id
-00a46ed:clear inline formatting from link tags
 c0a3dec:escape in url
-e66af00:url container precedence
 61876cf:roman alpha ambiguity
 f31b357:roman alpha ambiguity
 642d380:table end in verbatim inline