Convert unopened square-brackets into a hard error (#5414)

crates/typst-syntax/src/parser.rs

@@ -47,14 +47,9 @@ fn markup_exprs(p: &mut Parser, mut at_start: bool, stop_set: SyntaxSet) {
     debug_assert!(stop_set.contains(SyntaxKind::End));
     at_start |= p.had_newline();
     let mut nesting: usize = 0;
-    loop {
-        match p.current() {
-            SyntaxKind::LeftBracket => nesting += 1,
-            SyntaxKind::RightBracket if nesting > 0 => nesting -= 1,
-            _ if p.at_set(stop_set) => break,
-            _ => {}
-        }
-        markup_expr(p, at_start);
+    // Keep going if we're at a nested right-bracket regardless of the stop set.
+    while !p.at_set(stop_set) || (nesting > 0 && p.at(SyntaxKind::RightBracket)) {
+        markup_expr(p, at_start, &mut nesting);
         at_start = p.had_newline();
     }
 }
@@ -69,15 +64,12 @@ pub(super) fn reparse_markup(
 ) -> Option<Vec<SyntaxNode>> {
     let mut p = Parser::new(text, range.start, LexMode::Markup);
     *at_start |= p.had_newline();
-    while p.current_start() < range.end {
-        match p.current() {
-            SyntaxKind::LeftBracket => *nesting += 1,
-            SyntaxKind::RightBracket if *nesting > 0 => *nesting -= 1,
-            SyntaxKind::RightBracket if !top_level => break,
-            SyntaxKind::End => break,
-            _ => {}
+    while !p.end() && p.current_start() < range.end {
+        // If not top-level and at a new RightBracket, stop the reparse.
+        if !top_level && *nesting == 0 && p.at(SyntaxKind::RightBracket) {
+            break;
         }
-        markup_expr(&mut p, *at_start);
+        markup_expr(&mut p, *at_start, nesting);
         *at_start = p.had_newline();
     }
     (p.balanced && p.current_start() == range.end).then(|| p.finish())
@@ -86,8 +78,21 @@ pub(super) fn reparse_markup(
 /// Parses a single markup expression. This includes markup elements like text,
 /// headings, strong/emph, lists/enums, etc. This is also the entry point for
 /// parsing math equations and embedded code expressions.
-fn markup_expr(p: &mut Parser, at_start: bool) {
+fn markup_expr(p: &mut Parser, at_start: bool, nesting: &mut usize) {
     match p.current() {
+        SyntaxKind::LeftBracket => {
+            *nesting += 1;
+            p.convert_and_eat(SyntaxKind::Text);
+        }
+        SyntaxKind::RightBracket if *nesting > 0 => {
+            *nesting -= 1;
+            p.convert_and_eat(SyntaxKind::Text);
+        }
+        SyntaxKind::RightBracket => {
+            p.unexpected();
+            p.hint("try using a backslash escape: \\]");
+        }
+
         SyntaxKind::Text
         | SyntaxKind::Linebreak
         | SyntaxKind::Escape
@@ -108,9 +113,7 @@ fn markup_expr(p: &mut Parser, at_start: bool) {
         SyntaxKind::RefMarker => reference(p),
         SyntaxKind::Dollar => equation(p),
 
-        SyntaxKind::LeftBracket
-        | SyntaxKind::RightBracket
-        | SyntaxKind::HeadingMarker
+        SyntaxKind::HeadingMarker
         | SyntaxKind::ListMarker
         | SyntaxKind::EnumMarker
         | SyntaxKind::TermMarker
@@ -201,7 +204,7 @@ fn equation(p: &mut Parser) {
     let m = p.marker();
     p.enter_modes(LexMode::Math, AtNewline::Continue, |p| {
         p.assert(SyntaxKind::Dollar);
-        math(p, syntax_set!(Dollar, RightBracket, End));
+        math(p, syntax_set!(Dollar, End));
         p.expect_closing_delimiter(m, SyntaxKind::Dollar);
     });
     p.wrap(m, SyntaxKind::Equation);

tests/suite/scripting/blocks.typ

@@ -136,8 +136,45 @@
 #}
 
 --- single-right-bracket ---
+// Error: 1-2 unexpected closing bracket
+// Hint: 1-2 try using a backslash escape: \]
 ]
 
+--- right-bracket-nesting ---
+[
+= [ Hi ]]
+- how [
+  - are ]
+// Error: 10-11 unexpected closing bracket
+// Hint: 10-11 try using a backslash escape: \]
+  - error][]
+[[]]
+
+--- right-bracket-hash ---
+// Error: 2-3 unexpected closing bracket
+#]
+
+--- right-bracket-in-blocks ---
+// Error: 3-4 unclosed delimiter
+// Error: 6-7 unexpected closing bracket
+// Hint: 6-7 try using a backslash escape: \]
+[#{]}]
+
+// Error: 4-5 unexpected closing bracket
+// Hint: 4-5 try using a backslash escape: \]
+#[]]
+
+// Error: 4-5 unclosed delimiter
+// Error: 7-8 unexpected closing bracket
+// Hint: 7-8 try using a backslash escape: \]
+#[#{]}]
+
+// Error: 2-3 unclosed delimiter
+// Error: 3-4 unclosed delimiter
+// Error: 4-5 unexpected closing bracket
+// Hint: 4-5 try using a backslash escape: \]
+#{{]}}
+
 --- content-block-in-markup-scope ---
 // Content blocks also create a scope.
 #[#let x = 1]