Restructure parser files 🍔

5 files changed, 652 insertions, 650 deletions

diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 340e89ea..e7ab89f1 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -1,11 +1,654 @@
 //! Parsing and tokenization.
 
-mod escaping;
-mod parser;
-mod tokenizer;
+mod postprocess;
+mod tokens;
 
-pub use parser::*;
-pub use tokenizer::*;
+pub use tokens::*;
+
+use std::str::FromStr;
+
+use super::*;
+use crate::color::RgbaColor;
+use crate::compute::table::SpannedEntry;
+use crate::syntax::*;
+use crate::{Feedback, Pass};
+
+/// Parse a string of source code.
+pub fn parse(src: &str) -> Pass<SyntaxTree> {
+    Parser::new(src).parse()
+}
+
+struct Parser<'s> {
+    tokens: Tokens<'s>,
+    peeked: Option<Option<Spanned<Token<'s>>>>,
+    delimiters: Vec<(Pos, Token<'static>)>,
+    at_block_or_line_start: bool,
+    feedback: Feedback,
+}
+
+impl<'s> Parser<'s> {
+    fn new(src: &'s str) -> Self {
+        Self {
+            tokens: Tokens::new(src, TokenMode::Body),
+            peeked: None,
+            delimiters: vec![],
+            at_block_or_line_start: true,
+            feedback: Feedback::new(),
+        }
+    }
+
+    fn parse(mut self) -> Pass<SyntaxTree> {
+        let tree = self.parse_body_contents();
+        Pass::new(tree, self.feedback)
+    }
+}
+
+// Typesetting content.
+impl Parser<'_> {
+    fn parse_body_contents(&mut self) -> SyntaxTree {
+        let mut tree = SyntaxTree::new();
+
+        self.at_block_or_line_start = true;
+        while !self.eof() {
+            if let Some(node) = self.parse_node() {
+                tree.push(node);
+            }
+        }
+
+        tree
+    }
+
+    fn parse_node(&mut self) -> Option<Spanned<SyntaxNode>> {
+        let token = self.peek()?;
+        let end = Span::at(token.span.end);
+
+        // Set block or line start to false because most nodes have that effect, but
+        // remember the old value to actually check it for hashtags and because comments
+        // and spaces want to retain it.
+        let was_at_block_or_line_start = self.at_block_or_line_start;
+        self.at_block_or_line_start = false;
+
+        Some(match token.v {
+            // Starting from two newlines counts as a paragraph break, a single
+            // newline does not.
+            Token::Space(n) => {
+                if n == 0 {
+                    self.at_block_or_line_start = was_at_block_or_line_start;
+                } else if n >= 1 {
+                    self.at_block_or_line_start = true;
+                }
+
+                self.with_span(if n >= 2 {
+                    SyntaxNode::Parbreak
+                } else {
+                    SyntaxNode::Spacing
+                })
+            }
+
+            Token::LineComment(_) | Token::BlockComment(_) => {
+                self.at_block_or_line_start = was_at_block_or_line_start;
+                self.eat();
+                return None;
+            }
+
+            Token::LeftBracket => {
+                let call = self.parse_bracket_call(false);
+                self.at_block_or_line_start = false;
+                call.map(SyntaxNode::Call)
+            }
+
+            Token::Star => self.with_span(SyntaxNode::ToggleBolder),
+            Token::Underscore => self.with_span(SyntaxNode::ToggleItalic),
+            Token::Backslash => self.with_span(SyntaxNode::Linebreak),
+
+            Token::Hashtag if was_at_block_or_line_start => {
+                self.parse_heading().map(SyntaxNode::Heading)
+            }
+
+            Token::Raw { raw, backticks, terminated } => {
+                if !terminated {
+                    error!(@self.feedback, end, "expected backtick(s)");
+                }
+
+                let raw = if backticks > 1 {
+                    postprocess::process_raw(raw)
+                } else {
+                    Raw {
+                        lang: None,
+                        lines: postprocess::split_lines(raw),
+                        inline: true,
+                    }
+                };
+
+                self.with_span(SyntaxNode::Raw(raw))
+            }
+
+            Token::Text(text) => self.with_span(SyntaxNode::Text(text.to_string())),
+            Token::Hashtag => self.with_span(SyntaxNode::Text("#".to_string())),
+
+            Token::UnicodeEscape { sequence, terminated } => {
+                if !terminated {
+                    error!(@self.feedback, end, "expected closing brace");
+                }
+
+                if let Some(c) = postprocess::hex_to_char(sequence) {
+                    self.with_span(SyntaxNode::Text(c.to_string()))
+                } else {
+                    error!(@self.feedback, token.span, "invalid unicode escape sequence");
+                    self.eat();
+                    return None;
+                }
+            }
+
+            unexpected => {
+                error!(@self.feedback, token.span, "unexpected {}", unexpected.name());
+                self.eat();
+                return None;
+            }
+        })
+    }
+
+    fn parse_heading(&mut self) -> Spanned<Heading> {
+        let start = self.pos();
+        self.assert(Token::Hashtag);
+
+        let mut level = 0;
+        while self.peekv() == Some(Token::Hashtag) {
+            level += 1;
+            self.eat();
+        }
+
+        let span = Span::new(start, self.pos());
+        let level = level.span_with(span);
+
+        if level.v > 5 {
+            warning!(
+                @self.feedback, level.span,
+                "section depth larger than 6 has no effect",
+            );
+        }
+
+        self.skip_ws();
+
+        let mut tree = SyntaxTree::new();
+        while !self.eof() && !matches!(self.peekv(), Some(Token::Space(n)) if n >= 1) {
+            if let Some(node) = self.parse_node() {
+                tree.push(node);
+            }
+        }
+
+        let span = Span::new(start, self.pos());
+        Heading { level, tree }.span_with(span)
+    }
+}
+
+// Function calls.
+impl Parser<'_> {
+    fn parse_bracket_call(&mut self, chained: bool) -> Spanned<CallExpr> {
+        let before_bracket = self.pos();
+        if !chained {
+            self.start_group(Group::Bracket);
+            self.tokens.push_mode(TokenMode::Header);
+        }
+
+        let before_name = self.pos();
+        self.start_group(Group::Subheader);
+        self.skip_ws();
+        let name = self.parse_ident().unwrap_or_else(|| {
+            self.expected_found_or_at("function name", before_name);
+            Ident(String::new()).span_with(Span::at(before_name))
+        });
+
+        self.skip_ws();
+
+        let mut args = match self.eatv() {
+            Some(Token::Colon) => self.parse_table_contents().0,
+            Some(_) => {
+                self.expected_at("colon", name.span.end);
+                while self.eat().is_some() {}
+                TableExpr::new()
+            }
+            None => TableExpr::new(),
+        };
+
+        self.end_group();
+        self.skip_ws();
+        let (has_chained_child, end) = if self.peek().is_some() {
+            let item = self.parse_bracket_call(true);
+            let span = item.span;
+            let t = vec![item.map(SyntaxNode::Call)];
+            args.push(SpannedEntry::val(Expr::Tree(t).span_with(span)));
+            (true, span.end)
+        } else {
+            self.tokens.pop_mode();
+            (false, self.end_group().end)
+        };
+
+        let start = if chained { before_name } else { before_bracket };
+        let mut span = Span::new(start, end);
+
+        if self.check(Token::LeftBracket) && !has_chained_child {
+            self.start_group(Group::Bracket);
+            self.tokens.push_mode(TokenMode::Body);
+
+            let body = self.parse_body_contents();
+
+            self.tokens.pop_mode();
+            let body_span = self.end_group();
+
+            let expr = Expr::Tree(body);
+            args.push(SpannedEntry::val(expr.span_with(body_span)));
+            span.expand(body_span);
+        }
+
+        CallExpr { name, args }.span_with(span)
+    }
+
+    fn parse_paren_call(&mut self, name: Spanned<Ident>) -> Spanned<CallExpr> {
+        self.start_group(Group::Paren);
+        let args = self.parse_table_contents().0;
+        let args_span = self.end_group();
+        let span = Span::merge(name.span, args_span);
+        CallExpr { name, args }.span_with(span)
+    }
+}
+
+// Tables.
+impl Parser<'_> {
+    fn parse_table_contents(&mut self) -> (TableExpr, bool) {
+        let mut table = TableExpr::new();
+        let mut comma_and_keyless = true;
+
+        while {
+            self.skip_ws();
+            !self.eof()
+        } {
+            let (key, val) = if let Some(ident) = self.parse_ident() {
+                self.skip_ws();
+
+                match self.peekv() {
+                    Some(Token::Equals) => {
+                        self.eat();
+                        self.skip_ws();
+                        if let Some(value) = self.parse_expr() {
+                            (Some(ident), value)
+                        } else {
+                            self.expected("value");
+                            continue;
+                        }
+                    }
+
+                    Some(Token::LeftParen) => {
+                        let call = self.parse_paren_call(ident);
+                        (None, call.map(Expr::Call))
+                    }
+
+                    _ => (None, ident.map(Expr::Ident)),
+                }
+            } else if let Some(value) = self.parse_expr() {
+                (None, value)
+            } else {
+                self.expected("value");
+                continue;
+            };
+
+            let behind = val.span.end;
+            if let Some(key) = key {
+                comma_and_keyless = false;
+                table.insert(key.v.0, SpannedEntry::new(key.span, val));
+                self.feedback
+                    .decorations
+                    .push(Decoration::TableKey.span_with(key.span));
+            } else {
+                table.push(SpannedEntry::val(val));
+            }
+
+            if {
+                self.skip_ws();
+                self.eof()
+            } {
+                break;
+            }
+
+            self.expect_at(Token::Comma, behind);
+            comma_and_keyless = false;
+        }
+
+        let coercable = comma_and_keyless && !table.is_empty();
+        (table, coercable)
+    }
+}
+
+type Binop = fn(Box<Spanned<Expr>>, Box<Spanned<Expr>>) -> Expr;
+
+// Expressions and values.
+impl Parser<'_> {
+    fn parse_expr(&mut self) -> Option<Spanned<Expr>> {
+        self.parse_binops("summand", Self::parse_term, |token| match token {
+            Token::Plus => Some(Expr::Add),
+            Token::Hyphen => Some(Expr::Sub),
+            _ => None,
+        })
+    }
+
+    fn parse_term(&mut self) -> Option<Spanned<Expr>> {
+        self.parse_binops("factor", Self::parse_factor, |token| match token {
+            Token::Star => Some(Expr::Mul),
+            Token::Slash => Some(Expr::Div),
+            _ => None,
+        })
+    }
+
+    /// Parse expression of the form `<operand> (<op> <operand>)*`.
+    fn parse_binops(
+        &mut self,
+        operand_name: &str,
+        mut parse_operand: impl FnMut(&mut Self) -> Option<Spanned<Expr>>,
+        mut parse_op: impl FnMut(Token) -> Option<Binop>,
+    ) -> Option<Spanned<Expr>> {
+        let mut left = parse_operand(self)?;
+
+        self.skip_ws();
+        while let Some(token) = self.peek() {
+            if let Some(op) = parse_op(token.v) {
+                self.eat();
+                self.skip_ws();
+
+                if let Some(right) = parse_operand(self) {
+                    let span = Span::merge(left.span, right.span);
+                    let v = op(Box::new(left), Box::new(right));
+                    left = v.span_with(span);
+                    self.skip_ws();
+                    continue;
+                }
+
+                error!(
+                    @self.feedback, Span::merge(left.span, token.span),
+                    "missing right {}", operand_name,
+                );
+            }
+            break;
+        }
+
+        Some(left)
+    }
+
+    fn parse_factor(&mut self) -> Option<Spanned<Expr>> {
+        if let Some(hyph) = self.check_eat(Token::Hyphen) {
+            self.skip_ws();
+            if let Some(factor) = self.parse_factor() {
+                let span = Span::merge(hyph.span, factor.span);
+                Some(Expr::Neg(Box::new(factor)).span_with(span))
+            } else {
+                error!(@self.feedback, hyph.span, "dangling minus");
+                None
+            }
+        } else {
+            self.parse_value()
+        }
+    }
+
+    fn parse_value(&mut self) -> Option<Spanned<Expr>> {
+        let Spanned { v: token, span } = self.peek()?;
+        Some(match token {
+            // This could be a function call or an identifier.
+            Token::Ident(id) => {
+                let name = Ident(id.to_string()).span_with(span);
+                self.eat();
+                self.skip_ws();
+                if self.check(Token::LeftParen) {
+                    self.parse_paren_call(name).map(Expr::Call)
+                } else {
+                    name.map(Expr::Ident)
+                }
+            }
+
+            Token::Str { string, terminated } => {
+                if !terminated {
+                    self.expected_at("quote", span.end);
+                }
+                self.with_span(Expr::Str(postprocess::unescape_string(string)))
+            }
+
+            Token::Bool(b) => self.with_span(Expr::Bool(b)),
+            Token::Number(n) => self.with_span(Expr::Number(n)),
+            Token::Length(s) => self.with_span(Expr::Length(s)),
+            Token::Hex(s) => {
+                if let Ok(color) = RgbaColor::from_str(s) {
+                    self.with_span(Expr::Color(color))
+                } else {
+                    // Heal color by assuming black.
+                    error!(@self.feedback, span, "invalid color");
+                    let healed = RgbaColor::new_healed(0, 0, 0, 255);
+                    self.with_span(Expr::Color(healed))
+                }
+            }
+
+            // This could be a table or a parenthesized expression. We parse as
+            // a table in any case and coerce the table into a value if it is
+            // coercable (length 1 and no trailing comma).
+            Token::LeftParen => {
+                self.start_group(Group::Paren);
+                let (table, coercable) = self.parse_table_contents();
+                let span = self.end_group();
+
+                let expr = if coercable {
+                    table.into_values().next().expect("table is coercable").val.v
+                } else {
+                    Expr::Table(table)
+                };
+
+                expr.span_with(span)
+            }
+
+            // This is a content expression.
+            Token::LeftBrace => {
+                self.start_group(Group::Brace);
+                self.tokens.push_mode(TokenMode::Body);
+
+                let tree = self.parse_body_contents();
+
+                self.tokens.pop_mode();
+                let span = self.end_group();
+                Expr::Tree(tree).span_with(span)
+            }
+
+            // This is a bracketed function call.
+            Token::LeftBracket => {
+                let call = self.parse_bracket_call(false);
+                let tree = vec![call.map(SyntaxNode::Call)];
+                Expr::Tree(tree).span_with(span)
+            }
+
+            _ => return None,
+        })
+    }
+
+    fn parse_ident(&mut self) -> Option<Spanned<Ident>> {
+        self.peek().and_then(|token| match token.v {
+            Token::Ident(id) => Some(self.with_span(Ident(id.to_string()))),
+            _ => None,
+        })
+    }
+}
+
+// Error handling.
+impl Parser<'_> {
+    fn expect_at(&mut self, token: Token<'_>, pos: Pos) -> bool {
+        if self.check(token) {
+            self.eat();
+            true
+        } else {
+            self.expected_at(token.name(), pos);
+            false
+        }
+    }
+
+    fn expected(&mut self, thing: &str) {
+        if let Some(found) = self.eat() {
+            error!(
+                @self.feedback, found.span,
+                "expected {}, found {}", thing, found.v.name(),
+            );
+        } else {
+            error!(@self.feedback, Span::at(self.pos()), "expected {}", thing);
+        }
+    }
+
+    fn expected_at(&mut self, thing: &str, pos: Pos) {
+        error!(@self.feedback, Span::at(pos), "expected {}", thing);
+    }
+
+    fn expected_found_or_at(&mut self, thing: &str, pos: Pos) {
+        if self.eof() {
+            self.expected_at(thing, pos)
+        } else {
+            self.expected(thing);
+        }
+    }
+}
+
+// Parsing primitives.
+impl<'s> Parser<'s> {
+    fn start_group(&mut self, group: Group) {
+        let start = self.pos();
+        if let Some(start_token) = group.start() {
+            self.assert(start_token);
+        }
+        self.delimiters.push((start, group.end()));
+    }
+
+    fn end_group(&mut self) -> Span {
+        let peeked = self.peek();
+
+        let (start, end_token) = self.delimiters.pop().expect("group was not started");
+
+        if end_token != Token::Chain && peeked != None {
+            self.delimiters.push((start, end_token));
+            assert_eq!(peeked, None, "unfinished group");
+        }
+
+        match self.peeked.unwrap() {
+            Some(token) if token.v == end_token => {
+                self.peeked = None;
+                Span::new(start, token.span.end)
+            }
+            _ => {
+                let end = self.pos();
+                if end_token != Token::Chain {
+                    error!(
+                        @self.feedback, Span::at(end),
+                        "expected {}", end_token.name(),
+                    );
+                }
+                Span::new(start, end)
+            }
+        }
+    }
+
+    fn skip_ws(&mut self) {
+        while matches!(
+            self.peekv(),
+            Some(Token::Space(_)) |
+            Some(Token::LineComment(_)) |
+            Some(Token::BlockComment(_))
+        ) {
+            self.eat();
+        }
+    }
+
+    fn eatv(&mut self) -> Option<Token<'s>> {
+        self.eat().map(Spanned::value)
+    }
+
+    fn peekv(&mut self) -> Option<Token<'s>> {
+        self.peek().map(Spanned::value)
+    }
+
+    fn assert(&mut self, token: Token<'_>) {
+        assert!(self.check_eat(token).is_some());
+    }
+
+    fn check_eat(&mut self, token: Token<'_>) -> Option<Spanned<Token<'s>>> {
+        if self.check(token) { self.eat() } else { None }
+    }
+
+    /// Checks if the next token is of some kind
+    fn check(&mut self, token: Token<'_>) -> bool {
+        self.peekv() == Some(token)
+    }
+
+    fn with_span<T>(&mut self, v: T) -> Spanned<T> {
+        let span = self.eat().expect("expected token").span;
+        v.span_with(span)
+    }
+
+    fn eof(&mut self) -> bool {
+        self.peek().is_none()
+    }
+
+    fn eat(&mut self) -> Option<Spanned<Token<'s>>> {
+        let token = self.peek()?;
+        self.peeked = None;
+        Some(token)
+    }
+
+    fn peek(&mut self) -> Option<Spanned<Token<'s>>> {
+        let tokens = &mut self.tokens;
+        let token = (*self.peeked.get_or_insert_with(|| tokens.next()))?;
+
+        // Check for unclosed groups.
+        if Group::is_delimiter(token.v) {
+            if self.delimiters.iter().rev().any(|&(_, end)| token.v == end) {
+                return None;
+            }
+        }
+
+        Some(token)
+    }
+
+    fn pos(&self) -> Pos {
+        self.peeked
+            .flatten()
+            .map(|s| s.span.start)
+            .unwrap_or_else(|| self.tokens.pos())
+    }
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+enum Group {
+    Paren,
+    Bracket,
+    Brace,
+    Subheader,
+}
+
+impl Group {
+    fn is_delimiter(token: Token<'_>) -> bool {
+        matches!(
+            token,
+            Token::RightParen | Token::RightBracket | Token::RightBrace | Token::Chain
+        )
+    }
+
+    fn start(self) -> Option<Token<'static>> {
+        match self {
+            Self::Paren => Some(Token::LeftParen),
+            Self::Bracket => Some(Token::LeftBracket),
+            Self::Brace => Some(Token::LeftBrace),
+            Self::Subheader => None,
+        }
+    }
+
+    fn end(self) -> Token<'static> {
+        match self {
+            Self::Paren => Token::RightParen,
+            Self::Bracket => Token::RightBracket,
+            Self::Brace => Token::RightBrace,
+            Self::Subheader => Token::Chain,
+        }
+    }
+}
 
 #[cfg(test)]
 mod tests;
diff --git a/src/parse/parser.rs b/src/parse/parser.rs
deleted file mode 100644
index 3446af83..00000000
--- a/src/parse/parser.rs
+++ /dev/null
@@ -1,645 +0,0 @@
-use std::str::FromStr;
-
-use super::escaping::*;
-use super::*;
-use crate::color::RgbaColor;
-use crate::compute::table::SpannedEntry;
-use crate::syntax::*;
-use crate::{Feedback, Pass};
-
-/// Parse a string of source code.
-pub fn parse(src: &str) -> Pass<SyntaxTree> {
-    Parser::new(src).parse()
-}
-
-struct Parser<'s> {
-    tokens: Tokens<'s>,
-    peeked: Option<Option<Spanned<Token<'s>>>>,
-    delimiters: Vec<(Pos, Token<'static>)>,
-    at_block_or_line_start: bool,
-    feedback: Feedback,
-}
-
-impl<'s> Parser<'s> {
-    fn new(src: &'s str) -> Self {
-        Self {
-            tokens: Tokens::new(src, TokenMode::Body),
-            peeked: None,
-            delimiters: vec![],
-            at_block_or_line_start: true,
-            feedback: Feedback::new(),
-        }
-    }
-
-    fn parse(mut self) -> Pass<SyntaxTree> {
-        let tree = self.parse_body_contents();
-        Pass::new(tree, self.feedback)
-    }
-}
-
-// Typesetting content.
-impl Parser<'_> {
-    fn parse_body_contents(&mut self) -> SyntaxTree {
-        let mut tree = SyntaxTree::new();
-
-        self.at_block_or_line_start = true;
-        while !self.eof() {
-            if let Some(node) = self.parse_node() {
-                tree.push(node);
-            }
-        }
-
-        tree
-    }
-
-    fn parse_node(&mut self) -> Option<Spanned<SyntaxNode>> {
-        let token = self.peek()?;
-        let end = Span::at(token.span.end);
-
-        // Set block or line start to false because most nodes have that effect, but
-        // remember the old value to actually check it for hashtags and because comments
-        // and spaces want to retain it.
-        let was_at_block_or_line_start = self.at_block_or_line_start;
-        self.at_block_or_line_start = false;
-
-        Some(match token.v {
-            // Starting from two newlines counts as a paragraph break, a single
-            // newline does not.
-            Token::Space(n) => {
-                if n == 0 {
-                    self.at_block_or_line_start = was_at_block_or_line_start;
-                } else if n >= 1 {
-                    self.at_block_or_line_start = true;
-                }
-
-                self.with_span(if n >= 2 {
-                    SyntaxNode::Parbreak
-                } else {
-                    SyntaxNode::Spacing
-                })
-            }
-
-            Token::LineComment(_) | Token::BlockComment(_) => {
-                self.at_block_or_line_start = was_at_block_or_line_start;
-                self.eat();
-                return None;
-            }
-
-            Token::LeftBracket => {
-                let call = self.parse_bracket_call(false);
-                self.at_block_or_line_start = false;
-                call.map(SyntaxNode::Call)
-            }
-
-            Token::Star => self.with_span(SyntaxNode::ToggleBolder),
-            Token::Underscore => self.with_span(SyntaxNode::ToggleItalic),
-            Token::Backslash => self.with_span(SyntaxNode::Linebreak),
-
-            Token::Hashtag if was_at_block_or_line_start => {
-                self.parse_heading().map(SyntaxNode::Heading)
-            }
-
-            Token::Raw { raw, backticks, terminated } => {
-                if !terminated {
-                    error!(@self.feedback, end, "expected backtick(s)");
-                }
-
-                let raw = if backticks > 1 {
-                    process_raw(raw)
-                } else {
-                    Raw {
-                        lang: None,
-                        lines: split_lines(raw),
-                        inline: true,
-                    }
-                };
-
-                self.with_span(SyntaxNode::Raw(raw))
-            }
-
-            Token::Text(text) => self.with_span(SyntaxNode::Text(text.to_string())),
-            Token::Hashtag => self.with_span(SyntaxNode::Text("#".to_string())),
-
-            Token::UnicodeEscape { sequence, terminated } => {
-                if !terminated {
-                    error!(@self.feedback, end, "expected closing brace");
-                }
-
-                if let Some(c) = hex_to_char(sequence) {
-                    self.with_span(SyntaxNode::Text(c.to_string()))
-                } else {
-                    error!(@self.feedback, token.span, "invalid unicode escape sequence");
-                    self.eat();
-                    return None;
-                }
-            }
-
-            unexpected => {
-                error!(@self.feedback, token.span, "unexpected {}", unexpected.name());
-                self.eat();
-                return None;
-            }
-        })
-    }
-
-    fn parse_heading(&mut self) -> Spanned<Heading> {
-        let start = self.pos();
-        self.assert(Token::Hashtag);
-
-        let mut level = 0;
-        while self.peekv() == Some(Token::Hashtag) {
-            level += 1;
-            self.eat();
-        }
-
-        let span = Span::new(start, self.pos());
-        let level = level.span_with(span);
-
-        if level.v > 5 {
-            warning!(
-                @self.feedback, level.span,
-                "section depth larger than 6 has no effect",
-            );
-        }
-
-        self.skip_ws();
-
-        let mut tree = SyntaxTree::new();
-        while !self.eof() && !matches!(self.peekv(), Some(Token::Space(n)) if n >= 1) {
-            if let Some(node) = self.parse_node() {
-                tree.push(node);
-            }
-        }
-
-        let span = Span::new(start, self.pos());
-        Heading { level, tree }.span_with(span)
-    }
-}
-
-// Function calls.
-impl Parser<'_> {
-    fn parse_bracket_call(&mut self, chained: bool) -> Spanned<CallExpr> {
-        let before_bracket = self.pos();
-        if !chained {
-            self.start_group(Group::Bracket);
-            self.tokens.push_mode(TokenMode::Header);
-        }
-
-        let before_name = self.pos();
-        self.start_group(Group::Subheader);
-        self.skip_ws();
-        let name = self.parse_ident().unwrap_or_else(|| {
-            self.expected_found_or_at("function name", before_name);
-            Ident(String::new()).span_with(Span::at(before_name))
-        });
-
-        self.skip_ws();
-
-        let mut args = match self.eatv() {
-            Some(Token::Colon) => self.parse_table_contents().0,
-            Some(_) => {
-                self.expected_at("colon", name.span.end);
-                while self.eat().is_some() {}
-                TableExpr::new()
-            }
-            None => TableExpr::new(),
-        };
-
-        self.end_group();
-        self.skip_ws();
-        let (has_chained_child, end) = if self.peek().is_some() {
-            let item = self.parse_bracket_call(true);
-            let span = item.span;
-            let t = vec![item.map(SyntaxNode::Call)];
-            args.push(SpannedEntry::val(Expr::Tree(t).span_with(span)));
-            (true, span.end)
-        } else {
-            self.tokens.pop_mode();
-            (false, self.end_group().end)
-        };
-
-        let start = if chained { before_name } else { before_bracket };
-        let mut span = Span::new(start, end);
-
-        if self.check(Token::LeftBracket) && !has_chained_child {
-            self.start_group(Group::Bracket);
-            self.tokens.push_mode(TokenMode::Body);
-
-            let body = self.parse_body_contents();
-
-            self.tokens.pop_mode();
-            let body_span = self.end_group();
-
-            let expr = Expr::Tree(body);
-            args.push(SpannedEntry::val(expr.span_with(body_span)));
-            span.expand(body_span);
-        }
-
-        CallExpr { name, args }.span_with(span)
-    }
-
-    fn parse_paren_call(&mut self, name: Spanned<Ident>) -> Spanned<CallExpr> {
-        self.start_group(Group::Paren);
-        let args = self.parse_table_contents().0;
-        let args_span = self.end_group();
-        let span = Span::merge(name.span, args_span);
-        CallExpr { name, args }.span_with(span)
-    }
-}
-
-// Tables.
-impl Parser<'_> {
-    fn parse_table_contents(&mut self) -> (TableExpr, bool) {
-        let mut table = TableExpr::new();
-        let mut comma_and_keyless = true;
-
-        while {
-            self.skip_ws();
-            !self.eof()
-        } {
-            let (key, val) = if let Some(ident) = self.parse_ident() {
-                self.skip_ws();
-
-                match self.peekv() {
-                    Some(Token::Equals) => {
-                        self.eat();
-                        self.skip_ws();
-                        if let Some(value) = self.parse_expr() {
-                            (Some(ident), value)
-                        } else {
-                            self.expected("value");
-                            continue;
-                        }
-                    }
-
-                    Some(Token::LeftParen) => {
-                        let call = self.parse_paren_call(ident);
-                        (None, call.map(Expr::Call))
-                    }
-
-                    _ => (None, ident.map(Expr::Ident)),
-                }
-            } else if let Some(value) = self.parse_expr() {
-                (None, value)
-            } else {
-                self.expected("value");
-                continue;
-            };
-
-            let behind = val.span.end;
-            if let Some(key) = key {
-                comma_and_keyless = false;
-                table.insert(key.v.0, SpannedEntry::new(key.span, val));
-                self.feedback
-                    .decorations
-                    .push(Decoration::TableKey.span_with(key.span));
-            } else {
-                table.push(SpannedEntry::val(val));
-            }
-
-            if {
-                self.skip_ws();
-                self.eof()
-            } {
-                break;
-            }
-
-            self.expect_at(Token::Comma, behind);
-            comma_and_keyless = false;
-        }
-
-        let coercable = comma_and_keyless && !table.is_empty();
-        (table, coercable)
-    }
-}
-
-type Binop = fn(Box<Spanned<Expr>>, Box<Spanned<Expr>>) -> Expr;
-
-// Expressions and values.
-impl Parser<'_> {
-    fn parse_expr(&mut self) -> Option<Spanned<Expr>> {
-        self.parse_binops("summand", Self::parse_term, |token| match token {
-            Token::Plus => Some(Expr::Add),
-            Token::Hyphen => Some(Expr::Sub),
-            _ => None,
-        })
-    }
-
-    fn parse_term(&mut self) -> Option<Spanned<Expr>> {
-        self.parse_binops("factor", Self::parse_factor, |token| match token {
-            Token::Star => Some(Expr::Mul),
-            Token::Slash => Some(Expr::Div),
-            _ => None,
-        })
-    }
-
-    /// Parse expression of the form `<operand> (<op> <operand>)*`.
-    fn parse_binops(
-        &mut self,
-        operand_name: &str,
-        mut parse_operand: impl FnMut(&mut Self) -> Option<Spanned<Expr>>,
-        mut parse_op: impl FnMut(Token) -> Option<Binop>,
-    ) -> Option<Spanned<Expr>> {
-        let mut left = parse_operand(self)?;
-
-        self.skip_ws();
-        while let Some(token) = self.peek() {
-            if let Some(op) = parse_op(token.v) {
-                self.eat();
-                self.skip_ws();
-
-                if let Some(right) = parse_operand(self) {
-                    let span = Span::merge(left.span, right.span);
-                    let v = op(Box::new(left), Box::new(right));
-                    left = v.span_with(span);
-                    self.skip_ws();
-                    continue;
-                }
-
-                error!(
-                    @self.feedback, Span::merge(left.span, token.span),
-                    "missing right {}", operand_name,
-                );
-            }
-            break;
-        }
-
-        Some(left)
-    }
-
-    fn parse_factor(&mut self) -> Option<Spanned<Expr>> {
-        if let Some(hyph) = self.check_eat(Token::Hyphen) {
-            self.skip_ws();
-            if let Some(factor) = self.parse_factor() {
-                let span = Span::merge(hyph.span, factor.span);
-                Some(Expr::Neg(Box::new(factor)).span_with(span))
-            } else {
-                error!(@self.feedback, hyph.span, "dangling minus");
-                None
-            }
-        } else {
-            self.parse_value()
-        }
-    }
-
-    fn parse_value(&mut self) -> Option<Spanned<Expr>> {
-        let Spanned { v: token, span } = self.peek()?;
-        Some(match token {
-            // This could be a function call or an identifier.
-            Token::Ident(id) => {
-                let name = Ident(id.to_string()).span_with(span);
-                self.eat();
-                self.skip_ws();
-                if self.check(Token::LeftParen) {
-                    self.parse_paren_call(name).map(Expr::Call)
-                } else {
-                    name.map(Expr::Ident)
-                }
-            }
-
-            Token::Str { string, terminated } => {
-                if !terminated {
-                    self.expected_at("quote", span.end);
-                }
-                self.with_span(Expr::Str(unescape_string(string)))
-            }
-
-            Token::Bool(b) => self.with_span(Expr::Bool(b)),
-            Token::Number(n) => self.with_span(Expr::Number(n)),
-            Token::Length(s) => self.with_span(Expr::Length(s)),
-            Token::Hex(s) => {
-                if let Ok(color) = RgbaColor::from_str(s) {
-                    self.with_span(Expr::Color(color))
-                } else {
-                    // Heal color by assuming black.
-                    error!(@self.feedback, span, "invalid color");
-                    let healed = RgbaColor::new_healed(0, 0, 0, 255);
-                    self.with_span(Expr::Color(healed))
-                }
-            }
-
-            // This could be a table or a parenthesized expression. We parse as
-            // a table in any case and coerce the table into a value if it is
-            // coercable (length 1 and no trailing comma).
-            Token::LeftParen => {
-                self.start_group(Group::Paren);
-                let (table, coercable) = self.parse_table_contents();
-                let span = self.end_group();
-
-                let expr = if coercable {
-                    table.into_values().next().expect("table is coercable").val.v
-                } else {
-                    Expr::Table(table)
-                };
-
-                expr.span_with(span)
-            }
-
-            // This is a content expression.
-            Token::LeftBrace => {
-                self.start_group(Group::Brace);
-                self.tokens.push_mode(TokenMode::Body);
-
-                let tree = self.parse_body_contents();
-
-                self.tokens.pop_mode();
-                let span = self.end_group();
-                Expr::Tree(tree).span_with(span)
-            }
-
-            // This is a bracketed function call.
-            Token::LeftBracket => {
-                let call = self.parse_bracket_call(false);
-                let tree = vec![call.map(SyntaxNode::Call)];
-                Expr::Tree(tree).span_with(span)
-            }
-
-            _ => return None,
-        })
-    }
-
-    fn parse_ident(&mut self) -> Option<Spanned<Ident>> {
-        self.peek().and_then(|token| match token.v {
-            Token::Ident(id) => Some(self.with_span(Ident(id.to_string()))),
-            _ => None,
-        })
-    }
-}
-
-// Error handling.
-impl Parser<'_> {
-    fn expect_at(&mut self, token: Token<'_>, pos: Pos) -> bool {
-        if self.check(token) {
-            self.eat();
-            true
-        } else {
-            self.expected_at(token.name(), pos);
-            false
-        }
-    }
-
-    fn expected(&mut self, thing: &str) {
-        if let Some(found) = self.eat() {
-            error!(
-                @self.feedback, found.span,
-                "expected {}, found {}", thing, found.v.name(),
-            );
-        } else {
-            error!(@self.feedback, Span::at(self.pos()), "expected {}", thing);
-        }
-    }
-
-    fn expected_at(&mut self, thing: &str, pos: Pos) {
-        error!(@self.feedback, Span::at(pos), "expected {}", thing);
-    }
-
-    fn expected_found_or_at(&mut self, thing: &str, pos: Pos) {
-        if self.eof() {
-            self.expected_at(thing, pos)
-        } else {
-            self.expected(thing);
-        }
-    }
-}
-
-// Parsing primitives.
-impl<'s> Parser<'s> {
-    fn start_group(&mut self, group: Group) {
-        let start = self.pos();
-        if let Some(start_token) = group.start() {
-            self.assert(start_token);
-        }
-        self.delimiters.push((start, group.end()));
-    }
-
-    fn end_group(&mut self) -> Span {
-        let peeked = self.peek();
-
-        let (start, end_token) = self.delimiters.pop().expect("group was not started");
-
-        if end_token != Token::Chain && peeked != None {
-            self.delimiters.push((start, end_token));
-            assert_eq!(peeked, None, "unfinished group");
-        }
-
-        match self.peeked.unwrap() {
-            Some(token) if token.v == end_token => {
-                self.peeked = None;
-                Span::new(start, token.span.end)
-            }
-            _ => {
-                let end = self.pos();
-                if end_token != Token::Chain {
-                    error!(
-                        @self.feedback, Span::at(end),
-                        "expected {}", end_token.name(),
-                    );
-                }
-                Span::new(start, end)
-            }
-        }
-    }
-
-    fn skip_ws(&mut self) {
-        while matches!(
-            self.peekv(),
-            Some(Token::Space(_)) |
-            Some(Token::LineComment(_)) |
-            Some(Token::BlockComment(_))
-        ) {
-            self.eat();
-        }
-    }
-
-    fn eatv(&mut self) -> Option<Token<'s>> {
-        self.eat().map(Spanned::value)
-    }
-
-    fn peekv(&mut self) -> Option<Token<'s>> {
-        self.peek().map(Spanned::value)
-    }
-
-    fn assert(&mut self, token: Token<'_>) {
-        assert!(self.check_eat(token).is_some());
-    }
-
-    fn check_eat(&mut self, token: Token<'_>) -> Option<Spanned<Token<'s>>> {
-        if self.check(token) { self.eat() } else { None }
-    }
-
-    /// Checks if the next token is of some kind
-    fn check(&mut self, token: Token<'_>) -> bool {
-        self.peekv() == Some(token)
-    }
-
-    fn with_span<T>(&mut self, v: T) -> Spanned<T> {
-        let span = self.eat().expect("expected token").span;
-        v.span_with(span)
-    }
-
-    fn eof(&mut self) -> bool {
-        self.peek().is_none()
-    }
-
-    fn eat(&mut self) -> Option<Spanned<Token<'s>>> {
-        let token = self.peek()?;
-        self.peeked = None;
-        Some(token)
-    }
-
-    fn peek(&mut self) -> Option<Spanned<Token<'s>>> {
-        let tokens = &mut self.tokens;
-        let token = (*self.peeked.get_or_insert_with(|| tokens.next()))?;
-
-        // Check for unclosed groups.
-        if Group::is_delimiter(token.v) {
-            if self.delimiters.iter().rev().any(|&(_, end)| token.v == end) {
-                return None;
-            }
-        }
-
-        Some(token)
-    }
-
-    fn pos(&self) -> Pos {
-        self.peeked
-            .flatten()
-            .map(|s| s.span.start)
-            .unwrap_or_else(|| self.tokens.pos())
-    }
-}
-
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-enum Group {
-    Paren,
-    Bracket,
-    Brace,
-    Subheader,
-}
-
-impl Group {
-    fn is_delimiter(token: Token<'_>) -> bool {
-        matches!(
-            token,
-            Token::RightParen | Token::RightBracket | Token::RightBrace | Token::Chain
-        )
-    }
-
-    fn start(self) -> Option<Token<'static>> {
-        match self {
-            Self::Paren => Some(Token::LeftParen),
-            Self::Bracket => Some(Token::LeftBracket),
-            Self::Brace => Some(Token::LeftBrace),
-            Self::Subheader => None,
-        }
-    }
-
-    fn end(self) -> Token<'static> {
-        match self {
-            Self::Paren => Token::RightParen,
-            Self::Bracket => Token::RightBracket,
-            Self::Brace => Token::RightBrace,
-            Self::Subheader => Token::Chain,
-        }
-    }
-}
diff --git a/src/parse/escaping.rs b/src/parse/postprocess.rs
index 2e556d0c..ad4a9057 100644
--- a/src/parse/escaping.rs
+++ b/src/parse/postprocess.rs
@@ -1,3 +1,5 @@
+//! Post-processing of strings and raw blocks.
+
 use super::is_newline_char;
 use crate::syntax::{Ident, Raw};
 
diff --git a/src/parse/tests.rs b/src/parse/tests.rs
index 8ddf013d..a753378e 100644
--- a/src/parse/tests.rs
+++ b/src/parse/tests.rs
@@ -1,3 +1,5 @@
+//! Parser tests.
+
 #![allow(non_snake_case)]
 
 use std::fmt::Debug;
diff --git a/src/parse/tokenizer.rs b/src/parse/tokens.rs
index 720bec43..720bec43 100644
--- a/src/parse/tokenizer.rs
+++ b/src/parse/tokens.rs