Improve block body's diagnostics

dev_tests/src/pretty.rs

@@ -1,13 +0,0 @@
-// diagnostics_render.rs
-
-use rottlib::diagnostics::{Diagnostic};
-use rottlib::lexer::TokenizedFile;
-
-pub fn render_diagnostic(
-    diag: &Diagnostic,
-    _file: &TokenizedFile,
-    file_name: Option<&str>,
-    colors: bool,
-) {
-    diag.render(_file, file_name.unwrap_or("<default>"));
-}

dev_tests/src/uc_lexer_verify.rs

@@ -19,8 +19,6 @@ use rottlib::diagnostics::Diagnostic as Diag;
 use rottlib::lexer::TokenizedFile;
 use rottlib::parser::Parser;
 
-mod pretty;
-
 // ---------- CONFIG ----------
 const FILE_LIMIT: usize = 10000; // cap on files scanned
 const DIAG_SHOW_FIRST: usize = 12; // show first N diagnostics
@@ -35,6 +33,43 @@ const ALSO_PRINT_DEBUG_AFTER_PRETTY: bool = true;
 // chardet = "0.2"
 // encoding_rs = "0.8"
 
+fn render_diagnostic(diag: &Diag, file: &TokenizedFile<'_>, file_name: &str) {
+    diag.render(file, file_name);
+}
+
+fn render_diagnostics_window(diags: &[Diag], tf: &TokenizedFile<'_>, file_name: &str) {
+    let total = diags.len();
+    let first_n = DIAG_SHOW_FIRST.min(total);
+    let last_n = DIAG_SHOW_LAST.min(total.saturating_sub(first_n));
+
+    if total > first_n + last_n {
+        for (k, d) in diags.iter().take(first_n).enumerate() {
+            render_diagnostic(d, tf, file_name);
+            if ALSO_PRINT_DEBUG_AFTER_PRETTY {
+                eprintln!("#{}: {:#?}", k + 1, d);
+            }
+        }
+
+        eprintln!("... {} diagnostics omitted ...", total - (first_n + last_n));
+
+        let start = total - last_n;
+        for (offset, d) in diags.iter().skip(start).enumerate() {
+            let idx_global = start + offset + 1;
+            render_diagnostic(d, tf, file_name);
+            if ALSO_PRINT_DEBUG_AFTER_PRETTY {
+                eprintln!("#{idx_global}: {d:#?}");
+            }
+        }
+    } else {
+        for (k, d) in diags.iter().enumerate() {
+            render_diagnostic(d, tf, file_name);
+            if ALSO_PRINT_DEBUG_AFTER_PRETTY {
+                eprintln!("#{}: {:#?}", k + 1, d);
+            }
+        }
+    }
+}
+
 // Linux-only accurate RSS in MB. Fallback uses sysinfo.
 fn rss_mb() -> u64 {
     #[cfg(target_os = "linux")]
@@ -230,11 +265,24 @@ fn main() {
     mark("after_tokenize", t0);
 
     // If tokenization error: wait, dump tokens for the first failing file, then exit.
+    // If tokenization error: wait, print lexer diagnostics for the first failing file, then exit.
     if let Some(idx) = tk_error_idx {
-        let (bad_path, _) = &tokenized[idx];
-        wait_before_errors("Tokenization error found. Press Enter to dump tokens...");
-        eprintln!("--- Tokenization error in: {}", bad_path.display());
-        //bad_tf.dump_debug_layout(); // from DebugTools
+        let (bad_path, bad_tf) = &tokenized[idx];
+        wait_before_errors("Tokenization issues detected. Press Enter to print diagnostics...");
+
+        let fname = bad_path.display().to_string();
+
+        eprintln!("--- Tokenization issues in first failing file ---");
+        eprintln!("File: {fname}");
+
+        let diags = bad_tf.diagnostics();
+
+        if diags.is_empty() {
+            eprintln!("(no diagnostics captured)");
+        } else {
+            render_diagnostics_window(diags, bad_tf, &fname);
+        }
+
         std::process::exit(1);
     }
 
@@ -298,38 +346,8 @@ fn main() {
         if diags.is_empty() && fatal.is_none() {
             eprintln!("(no diagnostics captured)");
         } else {
-            let use_colors = is_terminal::is_terminal(io::stderr());
             let fname = path.display().to_string();
-            let total = diags.len();
-            let first_n = DIAG_SHOW_FIRST.min(total);
-            let last_n = DIAG_SHOW_LAST.min(total.saturating_sub(first_n));
-
-            if total > first_n + last_n {
-                // first window
-                for (k, d) in diags.iter().take(first_n).enumerate() {
-                    let s = pretty::render_diagnostic(d, tf, Some(&fname), use_colors);
-                    if ALSO_PRINT_DEBUG_AFTER_PRETTY {
-                        eprintln!("#{}: {:#?}", k + 1, d);
-                    }
-                }
-                eprintln!("... {} diagnostics omitted ...", total - (first_n + last_n));
-                // last window
-                let start = total - last_n;
-                for (offset, d) in diags.iter().skip(start).enumerate() {
-                    let idx_global = start + offset + 1;
-                    let s = pretty::render_diagnostic(d, tf, Some(&fname), use_colors);
-                    if ALSO_PRINT_DEBUG_AFTER_PRETTY {
-                        eprintln!("#{idx_global}: {d:#?}");
-                    }
-                }
-            } else {
-                for (k, d) in diags.iter().enumerate() {
-                    let s = pretty::render_diagnostic(d, tf, Some(&fname), use_colors);
-                    if ALSO_PRINT_DEBUG_AFTER_PRETTY {
-                        eprintln!("#{}: {:#?}", k + 1, d);
-                    }
-                }
-            }
+            render_diagnostics_window(&diags, tf, &fname);
         }
         std::process::exit(1);
     }

dev_tests/src/verify_expr.rs

@@ -7,73 +7,62 @@
 )]
 
 use rottlib::arena::Arena;
+use rottlib::diagnostics::Diagnostic;
 use rottlib::lexer::TokenizedFile;
 use rottlib::parser::Parser;
 
-mod pretty;
-
-// a * * *
-
-/// Expressions to test.
+/// Lexer-focused fixtures.
 ///
-/// Add, remove, or edit entries here.
-/// Using `(&str, &str)` gives each case a human-readable label.
-/// Expressions to test.
-///
-/// Add, remove, or edit entries here.
-/// Using `(&str, &str)` gives each case a human-readable label.
+/// Keep these small: the goal is to inspect lexer diagnostics and delimiter
+/// recovery behavior, not full parser behavior.
 const TEST_CASES: &[(&str, &str)] = &[
-    // P0022: invalid return value start
+    // P0027: `else` without a matching `if`
+    //
+    // `else` cannot start a standalone block item. The parser should report
+    // P0027 at `else`, then recover by bailing out of the current block.
     (
-        "files/P0022_01.uc",
-        "return ] ;",
-    ),
-    (
-        "files/P0022_02.uc",
-        "return\n    ]\n;\n",
-    ),
-    (
-        "files/P0022_03.uc",
-        "return\n}\n",
+        "files/P0027_01.uc",
+        "{\n    local bool bReady;\n    bReady = CheckReady();\n    else { StartMatch(); }\n    NotifyReady();\n}\n",
     ),
 
-    // P0023: invalid break value start
+    // P0027: `case` outside of a `switch`
+    //
+    // `case` is a switch-arm boundary, not a valid statement or expression
+    // starter in an ordinary block.
     (
-        "files/P0023_01.uc",
-        "break ] ;",
-    ),
-    (
-        "files/P0023_02.uc",
-        "break\n \n\n\n\n   ]\n;\n",
-    ),
-    (
-        "files/P0023_03.uc",
-        "break\n}\n",
+        "files/P0027_02.uc",
+        "{    local int Count;    Count = 3;    case 3:        Count++;    UpdateHud();}",
     ),
 
-    // P0024: goto target is missing or not a label token
+    // P0027: standalone `until` without a preceding `do`
+    //
+    // `until` is only meaningful as the tail of `do ... until`, so it should
+    // not be accepted as a normal block item.
     (
-        "files/P0024_01.uc",
-        "goto;",
+        "files/P0027_03.uc",
+        "{\n    local bool bDone;\n    bDone = false;\n    until (bDone)\n    TickWork();\n}\n",
     ),
+
+    // P0027: preprocessor/exec directive inside a statement block
+    //
+    // `#exec` is declaration/top-level-like syntax, not a valid statement or
+    // expression inside a braced statement block.
     (
-        "files/P0024_02.uc",
-        "goto\n    ;\n",
-    ),
-    (
-        "files/P0024_03.uc",
-        "goto\n    ]\n;\n",
-    ),
-    (
-        "files/P0024_04.uc",
-        "goto",
+        "files/P0027_04.uc",
+        "{\n    local int Count;\n    Count = 0;\n    #exec TEXTURE IMPORT NAME=Bad FILE=Bad.bmp\n    Count++;\n}\n",
     ),
 ];
 
+/// If true, also run the parser after tokenization.
+///
+/// For lexer-focused fixtures this is usually noisy, so keep it off unless you
+/// want to inspect how parser recovery behaves after lexer diagnostics.
+const RUN_PARSER: bool = true;
+
 /// If true, print the parsed expression using Debug formatting.
 const PRINT_PARSED_EXPR: bool = false;
 
-/// If true, print diagnostics even when parsing returned a value.
+const PRINT_LEXER_DIAGNOSTICS: bool = false;
 const ALWAYS_PRINT_DIAGNOSTICS: bool = true;
 
 fn main() {
@@ -82,8 +71,28 @@ fn main() {
     let mut had_any_problem = false;
 
     for (idx, (label, source)) in TEST_CASES.iter().enumerate() {
+        println!("============================================================");
+        println!("Case {}: {}", idx + 1, label);
+        println!("------------------------------------------------------------");
+
         let tf = TokenizedFile::tokenize(source);
 
+        let lexer_diagnostics = tf.diagnostics();
+
+        if lexer_diagnostics.is_empty() {
+            println!("Lexer diagnostics: none");
+        } else {
+            had_any_problem = true;
+
+            if PRINT_LEXER_DIAGNOSTICS {
+                println!("Lexer diagnostics:");
+                for diag in lexer_diagnostics {
+                    render_diagnostic(diag, &tf, Some(label), false);
+                }
+            }
+        }
+
+        if RUN_PARSER {
             let mut parser = Parser::new(&tf, &arena);
             let expr = parser.parse_expression();
 
@@ -93,13 +102,15 @@ fn main() {
             }
 
             if parser.diagnostics.is_empty() {
-            println!("Diagnostics: none");
+                println!("Parser diagnostics: none");
             } else {
                 had_any_problem = true;
+
                 if ALWAYS_PRINT_DIAGNOSTICS {
-                let use_colors = false;
-                for (k, diag) in parser.diagnostics.iter().enumerate() {
-                    pretty::render_diagnostic(diag, &tf, Some(label), use_colors);
+                    println!("Parser diagnostics:");
+                    for diag in &parser.diagnostics {
+                        render_diagnostic(diag, &tf, Some(label), false);
+                    }
                 }
             }
         }
@@ -108,10 +119,20 @@ fn main() {
     }
 
     println!("============================================================");
+
     if had_any_problem {
-        println!("Done. At least one case had tokenization or parse diagnostics.");
+        println!("Done. At least one case had lexer or parser diagnostics.");
         std::process::exit(1);
     } else {
         println!("Done. All cases completed without diagnostics.");
     }
 }
+
+fn render_diagnostic(
+    diag: &Diagnostic,
+    file: &TokenizedFile<'_>,
+    file_name: Option<&str>,
+    _colors: bool,
+) {
+    diag.render(file, file_name.unwrap_or("<default>"));
+}

rottlib/src/diagnostics/parse_error_diagnostics/block_items.rs

@@ -0,0 +1,111 @@
+use super::{Diagnostic, DiagnosticBuilder, FoundAt, found_at};
+use crate::lexer::{Token, TokenSpan, TokenizedFile};
+use crate::parser::ParseError;
+
+/// P0025
+pub(super) fn diagnostic_block_missing_semicolon_after_expression<'src>(
+    error: ParseError,
+    file: &TokenizedFile<'src>,
+) -> Diagnostic {
+    let expression_span = error.related_spans.get("expression_span").copied();
+
+    let primary_span = TokenSpan::new(error.blame_span.end);
+
+    let primary_text = match found_at(file, primary_span.end) {
+        FoundAt::Token(token_text) => format!("expected `;` before `{}`", token_text),
+        FoundAt::EndOfFile => "expected `;` before end of file".to_string(),
+        FoundAt::Unknown => "expected `;` here".to_string(),
+    };
+
+    let mut builder = DiagnosticBuilder::error("missing `;` after expression statement");
+
+    if let Some(expression_span) = expression_span {
+        if file.same_line(expression_span.start, primary_span.end) {
+            builder = builder.secondary_label(expression_span, "expression statement");
+        } else {
+            builder = builder.secondary_label(
+                TokenSpan::new(expression_span.end),
+                "expression statement ends here",
+            );
+        }
+    }
+
+    builder
+        .primary_label(primary_span, primary_text)
+        .code("P0025")
+        .build()
+}
+
+/// P0026
+pub(super) fn diagnostic_block_missing_closing_brace<'src>(
+    error: ParseError,
+    file: &TokenizedFile<'src>,
+) -> Diagnostic {
+    let left_brace_span = error.related_spans.get("left_brace").copied();
+    let unexpected_token_span = error.related_spans.get("unexpected_token").copied();
+
+    let (mut primary_span, primary_text) =
+        if let Some(unexpected_token_span) = unexpected_token_span {
+            let primary_span = TokenSpan::new(unexpected_token_span.end);
+
+            let primary_text = match found_at(file, primary_span.end) {
+                FoundAt::Token(token_text) => format!("expected `}}` before `{}`", token_text),
+                FoundAt::EndOfFile => "expected `}` before end of file".to_string(),
+                FoundAt::Unknown => "expected `}` here".to_string(),
+            };
+
+            (primary_span, primary_text)
+        } else {
+            (
+                TokenSpan::new(error.blame_span.end),
+                "expected `}` before end of file".to_string(),
+            )
+        };
+
+    let builder = DiagnosticBuilder::error("missing `}` to close block");
+
+    if let Some(left_brace_span) = left_brace_span
+        && !file.same_line(left_brace_span.start, primary_span.end)
+    {
+        primary_span.start = left_brace_span.start;
+    }
+
+    builder
+        .primary_label(primary_span, primary_text)
+        .code("P0026")
+        .build()
+}
+
+/// P0027
+pub(super) fn diagnostic_block_expected_item<'src>(
+    error: ParseError,
+    file: &TokenizedFile<'src>,
+) -> Diagnostic {
+    let primary_span = error.blame_span;
+
+    let (title, primary_text) = match file.token_at(primary_span.start).map(|data| data.token) {
+        Some(Token::ExecDirective) => (
+            "expected statement or expression, found `#exec` directive".to_string(),
+            "`#exec` directives are not allowed in a statement block".to_string(),
+        ),
+        _ => match found_at(file, primary_span.start) {
+            FoundAt::Token(token_text) => (
+                format!("expected statement or expression, found `{}`", token_text),
+                format!("unexpected `{}`", token_text),
+            ),
+            FoundAt::EndOfFile => (
+                "expected statement or expression, found end of file".to_string(),
+                "reached end of file here".to_string(),
+            ),
+            FoundAt::Unknown => (
+                "expected statement or expression".to_string(),
+                "expected statement or expression here".to_string(),
+            ),
+        },
+    };
+
+    DiagnosticBuilder::error(title)
+        .primary_label(primary_span, primary_text)
+        .code("P0027")
+        .build()
+}

rottlib/src/diagnostics/parse_error_diagnostics/control_flow_expressions.rs

@@ -263,7 +263,7 @@ pub(super) fn diagnostic_for_each_iterator_expression_expected<'src>(
     let control_keyword_text = control_keyword_span.and_then(|span| file.token_text(span.end));
 
     let found = found_at(file, error.blame_span.end);
-    let found_body_block_start = matches!(found, FoundAt::Token("{"));
+    let _ = matches!(found, FoundAt::Token("{"));
 
     let (header_text, primary_text) = match (control_keyword_text, found) {
         (Some(keyword_text), FoundAt::Token(token_text)) => {

rottlib/src/diagnostics/parse_error_diagnostics/mod.rs

@@ -10,9 +10,14 @@
 //! parser areas or grammar families.
 
 use super::{Diagnostic, DiagnosticBuilder};
+use crate::diagnostics::parse_error_diagnostics::block_items::{
+    diagnostic_block_expected_item, diagnostic_block_missing_closing_brace,
+    diagnostic_block_missing_semicolon_after_expression,
+};
 use crate::lexer::{TokenPosition, TokenSpan, TokenizedFile};
 use crate::parser::{ParseError, ParseErrorKind};
 
+mod block_items;
 mod control_flow_expressions;
 mod primary_expressions;
 
@@ -133,6 +138,14 @@ pub(crate) fn diagnostic_from_parse_error<'src>(
         }
         ParseErrorKind::BreakValueInvalidStart => diagnostic_break_value_invalid_start(error, file),
         ParseErrorKind::GotoMissingLabel => diagnostic_goto_missing_label(error, file),
+        // block_items.rs
+        ParseErrorKind::BlockMissingSemicolonAfterExpression => {
+            diagnostic_block_missing_semicolon_after_expression(error, file)
+        }
+        ParseErrorKind::BlockMissingClosingBrace => {
+            diagnostic_block_missing_closing_brace(error, file)
+        }
+        ParseErrorKind::BlockExpectedItem => diagnostic_block_expected_item(error, file),
 
         _ => DiagnosticBuilder::error(format!("error {:?} while parsing", error.kind))
             .primary_label(error.covered_span, "happened here")

rottlib/src/lexer/mod.rs

@@ -30,6 +30,7 @@ use std::ops::Range;
 
 use logos::Logos;
 
+use crate::diagnostics::{Diagnostic, DiagnosticBuilder};
 use raw_lexer::RawToken;
 
 pub use raw_lexer::BraceKind;
@@ -143,6 +144,10 @@ pub struct TokenizedFile<'src> {
     /// Records only exists for multiline tokens and ranges can be empty for
     /// lines that only contain line break boundary.
     multi_line_map: HashMap<BufferIndex, Vec<VisibleByteRange>>,
+    /// Sparse map between matched opening and closing delimiters.
+    delimiter_matches: DelimiterMatches,
+    /// Diagnostics produced during tokenization and delimiter matching.
+    diagnostics: Vec<Diagnostic>,
     /// Simple flag for marking erroneous state.
     had_errors: bool,
 }
@@ -205,6 +210,12 @@ struct Tokenizer<'src> {
     /// that started on `line_number`; it is consumed exactly once by
     /// [`Self::commit_current_line`].
     multi_line_start_line: Option<LineNumber>,
+    /// Tracks delimiter pairs and delimiter diagnostics.
+    delimiter_matcher: DelimiterMatcher,
+    /// Tracks crude line indentation for delimiter recovery diagnostics.
+    indent_tracker: IndentTracker,
+    /// Diagnostics produced while tokenizing.
+    diagnostics: Vec<Diagnostic>,
     /// Set to `true` if the lexer reported any error tokens.
     had_errors: bool,
 }
@@ -226,7 +237,8 @@ impl<'src> TokenizedFile<'src> {
                 RawToken::Error
             });
             let token_piece = make_token_data(Token::from(token), lexer.slice());
-            tokenizer.process_token_piece(token_piece);
+            let position = tokenizer.process_token_piece(token_piece);
+            tokenizer.after_token(position);
         }
         tokenizer.into_tokenized_file()
     }
@@ -244,6 +256,18 @@ impl<'src> TokenizedFile<'src> {
     pub const fn iter(&self) -> Tokens<'_, 'src> {
         Tokens::new(self)
     }
+
+    /// Returns diagnostics produced during tokenization and delimiter matching.
+    #[must_use]
+    pub fn diagnostics(&self) -> &[Diagnostic] {
+        &self.diagnostics
+    }
+
+    /// Returns the matching delimiter token, if this token is a matched delimiter.
+    #[must_use]
+    pub fn matching_delimiter(&self, position: TokenPosition) -> Option<TokenPosition> {
+        self.delimiter_matches.mate_of(position)
+    }
 }
 
 impl Line {
@@ -298,17 +322,22 @@ impl<'src> Tokenizer<'src> {
             line_number: 0,
             uncommitted_start_index: 0,
             multi_line_start_line: None,
+            delimiter_matcher: DelimiterMatcher::default(),
+            indent_tracker: IndentTracker::new(),
+            diagnostics: Vec::new(),
             had_errors: false,
         }
     }
 
     /// Handles a token span and dispatches to the appropriate handler.
-    fn process_token_piece(&mut self, token_piece: TokenData<'src>) {
+    fn process_token_piece(&mut self, token_piece: TokenData<'src>) -> TokenPosition {
+        let position = TokenPosition(self.buffer.len());
         if token_piece.token.can_span_lines() {
             self.process_multi_line_token(token_piece);
         } else {
             self.process_single_line_token(token_piece);
         }
+        position
     }
 
     /// Handles simple tokens that *never* span multiple lines, allowing us to
@@ -387,6 +416,26 @@ impl<'src> Tokenizer<'src> {
         }
     }
 
+    /// Runs post-processing that needs the token to already have a stable
+    /// [`TokenPosition`].
+    fn after_token(&mut self, position: TokenPosition) {
+        let token_piece = self.buffer[position.0];
+
+        if token_piece.token == Token::Error {
+            self.had_errors = true;
+            self.diagnostics
+                .push(diagnostic_invalid_token(position, token_piece.lexeme));
+        }
+
+        self.delimiter_matcher.observe(
+            position,
+            token_piece.token,
+            self.indent_tracker.current_indent(),
+        );
+
+        self.indent_tracker.observe_token(token_piece);
+    }
+
     /// Finishes tokenization, converting accumulated data into
     /// [`TokenizedFile`].
     fn into_tokenized_file(mut self) -> TokenizedFile<'src> {
@@ -399,6 +448,12 @@ impl<'src> Tokenizer<'src> {
             self.lines.push(Line::continued(from));
         }
 
+        let (delimiter_matches, delimiter_diagnostics) = self.delimiter_matcher.finish();
+        if !delimiter_diagnostics.is_empty() {
+            self.had_errors = true;
+        }
+        self.diagnostics.extend(delimiter_diagnostics);
+
         self.buffer.shrink_to_fit();
         self.lines.shrink_to_fit();
 
@@ -406,6 +461,8 @@ impl<'src> Tokenizer<'src> {
             buffer: self.buffer,
             lines: self.lines,
             multi_line_map: self.multi_line_map,
+            delimiter_matches,
+            diagnostics: self.diagnostics,
             had_errors: self.had_errors,
         }
     }
@@ -507,3 +564,409 @@ impl<'file, 'src> IntoIterator for &'file TokenizedFile<'src> {
         self.iter()
     }
 }
+
+/// Sparse map between matched delimiter tokens.
+///
+/// Stores both directions:
+///
+/// - opening delimiter -> closing delimiter
+/// - closing delimiter -> opening delimiter
+#[derive(Clone, Debug, Default, PartialEq, Eq)]
+pub struct DelimiterMatches {
+    mates: HashMap<TokenPosition, TokenPosition>,
+}
+
+impl DelimiterMatches {
+    /// Returns the matching delimiter token for `position`, if known.
+    #[must_use]
+    pub fn mate_of(&self, position: TokenPosition) -> Option<TokenPosition> {
+        self.mates.get(&position).copied()
+    }
+
+    fn insert_pair(&mut self, left: TokenPosition, right: TokenPosition) {
+        self.mates.insert(left, right);
+        self.mates.insert(right, left);
+    }
+}
+
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
+enum DelimiterKind {
+    Parenthesis,
+    Bracket,
+    Brace,
+}
+
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
+enum DelimiterSide {
+    Open,
+    Close,
+}
+
+#[derive(Clone, Copy, Debug)]
+struct OpenDelimiter {
+    kind: DelimiterKind,
+    position: TokenPosition,
+    indent: usize,
+}
+
+#[derive(Debug, Default)]
+struct DelimiterMatcher {
+    stack: Vec<OpenDelimiter>,
+    matches: DelimiterMatches,
+    diagnostics: Vec<Diagnostic>,
+    stopped_at_defaultproperties: bool,
+}
+
+impl DelimiterMatcher {
+    fn handle_defaultproperties_boundary(&mut self, defaultproperties_position: TokenPosition) {
+        while let Some(open) = self.stack.pop() {
+            self.diagnostics
+                .push(diagnostic_unclosed_delimiter_before_defaultproperties(
+                    open,
+                    defaultproperties_position,
+                ));
+        }
+    }
+
+    fn observe(&mut self, position: TokenPosition, token: Token, indent: usize) {
+        if self.stopped_at_defaultproperties {
+            return;
+        }
+
+        if token == Token::Keyword(Keyword::DefaultProperties) {
+            self.handle_defaultproperties_boundary(position);
+            self.stopped_at_defaultproperties = true;
+            return;
+        }
+
+        let Some((side, kind)) = delimiter_of(token) else {
+            return;
+        };
+
+        match side {
+            DelimiterSide::Open => {
+                self.stack.push(OpenDelimiter {
+                    kind,
+                    position,
+                    indent,
+                });
+            }
+            DelimiterSide::Close => {
+                self.handle_close(kind, position, indent);
+            }
+        }
+    }
+
+    fn handle_close(
+        &mut self,
+        close_kind: DelimiterKind,
+        close_position: TokenPosition,
+        close_indent: usize,
+    ) {
+        let Some(top) = self.stack.last().copied() else {
+            self.diagnostics
+                .push(diagnostic_unexpected_closing_delimiter(
+                    close_kind,
+                    close_position,
+                ));
+            return;
+        };
+
+        if top.kind == close_kind {
+            let open = self.stack.pop().expect("stack top was just checked");
+            self.matches.insert_pair(open.position, close_position);
+            return;
+        }
+
+        let earlier_same_kind = self.stack.iter().rposition(|open| open.kind == close_kind);
+
+        match earlier_same_kind {
+            Some(index) => {
+                let bad_open = top;
+                let recovered_open = self.stack[index];
+
+                self.diagnostics
+                    .push(diagnostic_unclosed_delimiter_before_later_close(
+                        bad_open,
+                        close_kind,
+                        close_position,
+                        recovered_open,
+                        recovered_open.indent == close_indent,
+                    ));
+
+                while self.stack.len() - 1 > index {
+                    self.stack.pop();
+                }
+
+                let open = self
+                    .stack
+                    .pop()
+                    .expect("same-kind delimiter was found on the stack");
+
+                self.matches.insert_pair(open.position, close_position);
+            }
+            None => {
+                let bad_open = self.stack.pop().expect("stack top was known to exist");
+
+                self.diagnostics
+                    .push(diagnostic_mismatched_closing_delimiter(
+                        bad_open,
+                        close_kind,
+                        close_position,
+                    ));
+            }
+        }
+    }
+
+    fn finish(mut self) -> (DelimiterMatches, Vec<Diagnostic>) {
+        if !self.stopped_at_defaultproperties {
+            while let Some(open) = self.stack.pop() {
+                self.diagnostics
+                    .push(diagnostic_unclosed_delimiter_at_eof(open));
+            }
+        }
+
+        (self.matches, self.diagnostics)
+    }
+}
+
+fn delimiter_of(token: Token) -> Option<(DelimiterSide, DelimiterKind)> {
+    match token {
+        Token::LeftParenthesis => Some((DelimiterSide::Open, DelimiterKind::Parenthesis)),
+        Token::RightParenthesis => Some((DelimiterSide::Close, DelimiterKind::Parenthesis)),
+
+        Token::LeftBracket => Some((DelimiterSide::Open, DelimiterKind::Bracket)),
+        Token::RightBracket => Some((DelimiterSide::Close, DelimiterKind::Bracket)),
+
+        Token::LeftBrace => Some((DelimiterSide::Open, DelimiterKind::Brace)),
+        Token::RightBrace => Some((DelimiterSide::Close, DelimiterKind::Brace)),
+
+        _ => None,
+    }
+}
+
+fn open_delimiter_text(kind: DelimiterKind) -> &'static str {
+    match kind {
+        DelimiterKind::Parenthesis => "(",
+        DelimiterKind::Bracket => "[",
+        DelimiterKind::Brace => "{",
+    }
+}
+
+fn close_delimiter_text(kind: DelimiterKind) -> &'static str {
+    match kind {
+        DelimiterKind::Parenthesis => ")",
+        DelimiterKind::Bracket => "]",
+        DelimiterKind::Brace => "}",
+    }
+}
+
+/// Crude indentation tracker used only for delimiter recovery diagnostics.
+///
+/// This is intentionally simple. It assumes indentation is represented by a
+/// run of whitespace tokens before the first non-trivia token on a physical
+/// line. It does not try to normalize tabs or handle every multiline trivia
+/// edge case precisely, because indentation is only a diagnostic heuristic.
+#[derive(Clone, Copy, Debug)]
+struct IndentTracker {
+    current_indent: usize,
+    before_first_nontrivia_on_line: bool,
+}
+
+impl IndentTracker {
+    fn new() -> Self {
+        Self {
+            current_indent: 0,
+            before_first_nontrivia_on_line: true,
+        }
+    }
+
+    fn current_indent(&self) -> usize {
+        self.current_indent
+    }
+
+    fn observe_token(&mut self, token_piece: TokenData<'_>) {
+        if token_is_newline(token_piece.token) {
+            self.current_indent = 0;
+            self.before_first_nontrivia_on_line = true;
+            return;
+        }
+
+        if self.before_first_nontrivia_on_line && token_is_whitespace(token_piece.token) {
+            self.current_indent += token_piece.lexeme.chars().count();
+            return;
+        }
+
+        if token_is_trivia(token_piece.token) {
+            return;
+        }
+
+        self.before_first_nontrivia_on_line = false;
+    }
+}
+
+fn token_is_newline(token: Token) -> bool {
+    matches!(token, Token::Newline)
+}
+
+fn token_is_whitespace(token: Token) -> bool {
+    matches!(token, Token::Whitespace)
+}
+
+fn token_is_trivia(token: Token) -> bool {
+    matches!(
+        token,
+        Token::Whitespace | Token::Newline | Token::LineComment | Token::BlockComment
+    )
+}
+
+fn diagnostic_invalid_token(position: TokenPosition, lexeme: &str) -> Diagnostic {
+    let shown = display_lexeme(lexeme);
+
+    DiagnosticBuilder::error(format!("invalid token: {}", shown))
+        .code("L0001")
+        .primary_label(
+            TokenSpan::new(position),
+            format!("invalid token: {}", shown),
+        )
+        .build()
+}
+
+fn diagnostic_unexpected_closing_delimiter(
+    close_kind: DelimiterKind,
+    close_position: TokenPosition,
+) -> Diagnostic {
+    let close = close_delimiter_text(close_kind);
+
+    DiagnosticBuilder::error(format!("unexpected closing delimiter: `{}`", close))
+        .code("L0002")
+        .primary_label(
+            TokenSpan::new(close_position),
+            "unexpected closing delimiter",
+        )
+        .build()
+}
+
+fn diagnostic_unclosed_delimiter_before_later_close(
+    bad_open: OpenDelimiter,
+    close_kind: DelimiterKind,
+    close_position: TokenPosition,
+    recovered_open: OpenDelimiter,
+    same_indent: bool,
+) -> Diagnostic {
+    let bad_open_text = open_delimiter_text(bad_open.kind);
+    let close_text = close_delimiter_text(close_kind);
+    let recovered_open_text = open_delimiter_text(recovered_open.kind);
+
+    let mut builder =
+        DiagnosticBuilder::error(format!("unclosed delimiter before `{}`", close_text))
+            .code("L0003")
+            .primary_label(
+                TokenSpan::new(bad_open.position),
+                format!(
+                    "this `{}` is not closed before `{}`",
+                    bad_open_text, close_text
+                ),
+            )
+            .secondary_label(
+                TokenSpan::new(close_position),
+                format!(
+                    "this `{}` is matched with the earlier `{}`",
+                    close_text, recovered_open_text
+                ),
+            );
+
+    if same_indent {
+        builder = builder.secondary_label(
+            TokenSpan::new(recovered_open.position),
+            format!(
+                "this `{}` is likely the intended match",
+                recovered_open_text,
+            ),
+        );
+    }
+
+    builder.build()
+}
+
+fn diagnostic_mismatched_closing_delimiter(
+    bad_open: OpenDelimiter,
+    close_kind: DelimiterKind,
+    close_position: TokenPosition,
+) -> Diagnostic {
+    let open = open_delimiter_text(bad_open.kind);
+    let close = close_delimiter_text(close_kind);
+
+    DiagnosticBuilder::error(format!("mismatched closing delimiter: `{}`", close))
+        .code("L0004")
+        .primary_label(
+            TokenSpan::new(close_position),
+            format!("closing delimiter does not match `{}`", open),
+        )
+        .secondary_label(
+            TokenSpan::new(bad_open.position),
+            format!("`{}` opened here", open),
+        )
+        .build()
+}
+
+fn diagnostic_unclosed_delimiter_at_eof(open: OpenDelimiter) -> Diagnostic {
+    let open_text = open_delimiter_text(open.kind);
+
+    DiagnosticBuilder::error(format!("unclosed delimiter: `{}`", open_text))
+        .code("L0005")
+        .primary_label(
+            TokenSpan::new(open.position),
+            format!("this `{}` was never closed", open_text),
+        )
+        .build()
+}
+
+fn diagnostic_unclosed_delimiter_before_defaultproperties(
+    open: OpenDelimiter,
+    defaultproperties_position: TokenPosition,
+) -> Diagnostic {
+    let open_text = open_delimiter_text(open.kind);
+
+    DiagnosticBuilder::error("unclosed delimiter before `defaultproperties`")
+        .code("L0006")
+        .primary_label(
+            TokenSpan::new(open.position),
+            format!("this `{}` is not closed before `defaultproperties`", open_text),
+        )
+        .secondary_label(
+            TokenSpan::new(defaultproperties_position),
+            "delimiter matching stops at `defaultproperties`",
+        )
+        .build()
+}
+
+fn display_lexeme(lexeme: &str) -> String {
+    if lexeme.is_empty() {
+        return "<empty>".to_string();
+    }
+
+    if lexeme == "`" {
+        return "backtick".to_string();
+    }
+
+    let escaped: String = lexeme.chars().flat_map(char::escape_default).collect();
+
+    const MAX_DISPLAY_CHARS: usize = 32;
+
+    let mut display = String::new();
+    let mut chars = escaped.chars();
+
+    for _ in 0..MAX_DISPLAY_CHARS {
+        let Some(character) = chars.next() else {
+            return format!("`{}`", display);
+        };
+        display.push(character);
+    }
+
+    if chars.next().is_some() {
+        display.push_str("...");
+    }
+
+    format!("`{}`", display)
+}

rottlib/src/lexer/raw_lexer.rs

@@ -59,7 +59,7 @@ pub enum BraceKind {
 #[logos(extras = LexerState)]
 pub enum RawToken {
     // # Compiler/directive keywords
-    #[regex(r"(?i)#exec[^\r\n]*(?:\r\n|\n|\r)?")]
+    #[regex(r"(?i)#exec[^\r\n]*")]
     ExecDirective,
     #[regex("(?i)cpptext", |lex| {
         if is_next_nontrivia_left_brace(lex) {

rottlib/src/parser/cursor.rs

@@ -364,6 +364,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
     }
 
     /// Ensures that parsing has advanced past `old_position`. 
+    // TODO: must be given peeked value!
     ///
     /// This is intended as a safeguard against infinite-loop bugs while
     /// recovering from invalid input. In debug builds it asserts that progress
@@ -384,4 +385,31 @@ impl<'src, 'arena> Parser<'src, 'arena> {
             }
         }
     }
+
+    /// Returns the first significant token after `position`, without consuming it.
+    ///
+    /// This buffers through the cursor, so trivia is still recorded normally and
+    /// insignificant tokens are skipped consistently with the rest of the parser.
+    ///
+    /// Returns `None` if the stream ends before a later significant token is found.
+    #[must_use]
+    pub(crate) fn peek_token_after_position(&mut self, position: TokenPosition) -> Option<Token> {
+        let mut lookahead = 0usize;
+
+        loop {
+            self.cursor
+                .ensure_lookahead_available(lookahead, &mut self.trivia);
+
+            let Some((token_position, token_data)) = self.cursor.lookahead_buffer.get(lookahead)
+            else {
+                return None;
+            };
+
+            if *token_position > position {
+                return Some(token_data.token);
+            }
+
+            lookahead += 1;
+        }
+    }
 }

rottlib/src/parser/errors.rs

@@ -64,6 +64,12 @@ pub enum ParseErrorKind {
     BreakValueInvalidStart,
     /// P0024
     GotoMissingLabel,
+    /// P0025
+    BlockMissingSemicolonAfterExpression,
+    /// P0026
+    BlockMissingClosingBrace,
+    /// P0027
+    BlockExpectedItem,
     // ================== Old errors to be thrown away! ==================
     /// Expression inside `(...)` could not be parsed and no closing `)`
     /// was found.
@@ -83,11 +89,7 @@ pub enum ParseErrorKind {
 
     TypeSpecClassMissingInnerType,
     TypeSpecClassMissingClosingAngle,
-    /// An expression inside a block is not terminated with `;`.
-    BlockMissingSemicolonAfterExpression,
-    /// A statement inside a block is not terminated with `;`.
     BlockMissingSemicolonAfterStatement,
-    BlockMissingClosingBrace,
     /// `switch` has no body (missing matching braces).
     SwitchMissingBody,
     /// The first top-level item in a `switch` body is not a `case`.

rottlib/src/parser/grammar/class.rs

@@ -357,7 +357,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
                 Ok(rule) => rules.push(rule),
                 Err(error) => {
                     self.report_error(error);
-                    self.recover_until(SyncLevel::Statement);
+                    self.recover_until(SyncLevel::StatementStart);
                     let _ = self.eat(Token::Semicolon);
                     if !self.ensure_progress_or_break(loop_start) {
                         break;
@@ -899,7 +899,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
                 }
                 Some((_, _)) if declarators.is_empty() => {
                     self.report_error_here(ParseErrorKind::DeclBadVariableIdentifier);
-                    self.recover_until(SyncLevel::Statement);
+                    self.recover_until(SyncLevel::StatementStart);
                     let _ = self.eat(Token::Semicolon);
                     break;
                 }

rottlib/src/parser/grammar/declarations/enum_definition.rs

@@ -104,7 +104,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
         variants: &mut ArenaVec<'arena, IdentifierToken>,
     ) -> ControlFlow<()> {
         self.parse_identifier(ParseErrorKind::EnumBadVariant)
-            .sync_error_until(self, SyncLevel::Statement)
+            .sync_error_until(self, SyncLevel::StatementStart)
             .ok_or_report(self)
             .map_or(ControlFlow::Break(()), |variant| {
                 variants.push(variant);
@@ -122,7 +122,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
         let Some(variant) = self
             .parse_identifier(ParseErrorKind::EnumBadVariant)
             .widen_error_span_from(error_start_position)
-            .sync_error_until(self, SyncLevel::Statement)
+            .sync_error_until(self, SyncLevel::StatementStart)
             .ok_or_report(self)
         else {
             // If we don't even get a good identifier - error is different

rottlib/src/parser/grammar/declarations/struct_definition.rs

@@ -93,7 +93,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
                 self.advance();
                 if !self.eat(Token::CppBlock) {
                     self.report_error_here(ParseErrorKind::CppDirectiveMissingCppBlock);
-                    self.recover_until(SyncLevel::Statement);
+                    self.recover_until(SyncLevel::StatementStart);
                 }
                 StructBodyItemParseOutcome::Skip
             }

rottlib/src/parser/grammar/declarations/variable_declarators.rs

@@ -104,7 +104,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
     ) -> ControlFlow<()> {
         if let Some(parsed_declarator) = self
             .parse_variable_declarator()
-            .sync_error_until(self, SyncLevel::Statement)
+            .sync_error_until(self, SyncLevel::StatementStart)
             .ok_or_report(self)
         {
             declarators.push(parsed_declarator);
@@ -122,7 +122,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
         if let Some(parsed_declarator) = self
             .parse_variable_declarator()
             .widen_error_span_from(error_start_position)
-            .sync_error_until(self, SyncLevel::Statement)
+            .sync_error_until(self, SyncLevel::StatementStart)
             .ok_or_report(self)
         {
             self.make_error_at_last_consumed(ParseErrorKind::DeclNoSeparatorBetweenVariableDeclarations)

rottlib/src/parser/grammar/expression/block.rs

@@ -4,106 +4,187 @@
 //! function, loop, state, and similar constructs after the opening `{`
 //! has been consumed.
 
-use crate::arena::ArenaVec;
-use crate::ast::{BlockBody, Expression, ExpressionRef, Statement, StatementRef};
+use crate::ast::{BlockBody, Expression, ExpressionRef, Statement, StatementList, StatementRef};
 use crate::lexer::{Token, TokenPosition, TokenSpan};
-use crate::parser::{ParseErrorKind, Parser};
+use crate::parser::{ParseErrorKind, ParseResult, Parser, ResultRecoveryExt, SyncLevel};
 
 impl<'src, 'arena> Parser<'src, 'arena> {
-    /// Parses a `{ ... }` block after the opening `{` has been consumed.
+    /// Parses a braced block body into an [`Expression::Block`].
     ///
-    /// Consumes tokens until the matching `}` and returns an
-    /// [`Expression::Block`] whose span covers the entire block, from
-    /// `opening_brace_position` to the closing `}`.
+    /// The opening `{` must already have been consumed. The returned block's
+    /// span covers the whole block, from `left_brace_position` through
+    /// the closing `}`.
     ///
-    /// On premature end-of-file, returns a best-effort block.
+    /// On premature end-of-file, reports the missing `}` and returns
+    /// a best-effort block.
     #[must_use]
-    pub(crate) fn parse_block_tail(
+    pub(crate) fn parse_block_body_tail(
         &mut self,
-        opening_brace_position: TokenPosition,
+        left_brace_position: TokenPosition,
     ) -> ExpressionRef<'src, 'arena> {
         let BlockBody { statements, span } =
-            self.parse_braced_block_statements_tail(opening_brace_position);
+            self.parse_braced_block_statements_tail(left_brace_position);
         self.arena.alloc_node(Expression::Block(statements), span)
     }
 
-    /// Parses a `{ ... }` block after the opening `{` has been consumed.
+    /// Parses the statements in a braced block body.
     ///
-    /// Consumes tokens until the matching `}` and returns the contained
-    /// statements together with a span that covers the entire block, from
-    /// `opening_brace_position` to the closing `}`.
+    /// The opening `{` must already have been consumed. Returns the parsed
+    /// statements and a span covering the whole block, from
+    /// `left_brace_position` through the closing `}`.
     ///
-    /// On premature end-of-file, returns a best-effort statement list and span.
+    /// On premature end-of-file, reports the missing `}` and returns
+    /// a best-effort body.
     #[must_use]
     pub(crate) fn parse_braced_block_statements_tail(
         &mut self,
-        opening_brace_position: TokenPosition,
+        left_brace_position: TokenPosition,
     ) -> BlockBody<'src, 'arena> {
         let mut statements = self.arena.vec();
         while let Some((token, token_position)) = self.peek_token_and_position() {
             if token == Token::RightBrace {
                 self.advance(); // '}'
-                let span = TokenSpan::range(opening_brace_position, token_position);
+                let span = TokenSpan::range(left_brace_position, token_position);
                 return BlockBody { statements, span };
             }
-            self.parse_next_block_item_into(&mut statements);
+            match self.parse_and_append_next_block_item(&mut statements) {
+                Ok(()) => {
+                    // Guard against parser bugs that would otherwise leave
+                    // block parsing stuck on the same token.
                     self.ensure_forward_progress(token_position);
                 }
-        // Reached EOF without a closing `}`
-        self.report_error_here(ParseErrorKind::BlockMissingClosingBrace);
+                Err(error) => {
+                    // Item-level recovery failed,
+                    // so escalate to the block boundary.
+                    let error = error.sync_error_at_matching_delimiter(self, left_brace_position);
+                    let error_statement = error.fallback(self);
+                    statements.push(error_statement);
                     let span = TokenSpan::range(
-            opening_brace_position,
+                        left_brace_position,
                         self.last_consumed_position_or_start(),
                     );
+                    return BlockBody { statements, span };
+                }
+            }
+        }
+        let eof_position = self.peek_position_or_eof();
+        self.make_error_at(ParseErrorKind::BlockMissingClosingBrace, eof_position)
+            .related_token("left_brace", left_brace_position)
+            .report(self);
+        let span = TokenSpan::range(left_brace_position, self.last_consumed_position_or_start());
+
         BlockBody { statements, span }
     }
 
-    /// Parses one statement inside a `{ ... }` block and appends it to
-    /// `statements`.
+    /// Parses one statement-like item inside a `{ ... }` block and appends it
+    /// to `statements`.
     ///
     /// This method never consumes the closing `}` and is only meant to be
-    /// called while parsing inside a block. It always appends at least one
-    /// statement, even in the presence of syntax errors.
-    pub(crate) fn parse_next_block_item_into(
+    /// called while parsing inside a block.
+    ///
+    /// On success, it appends exactly one statement. If neither a statement nor
+    /// an expression statement can be recovered locally, it returns
+    /// an unreported error so the enclosing block parser can recover at
+    /// block level.
+    pub(crate) fn parse_and_append_next_block_item(
         &mut self,
-        statements: &mut ArenaVec<'arena, StatementRef<'src, 'arena>>,
-    ) {
-        let mut next_statement = self.parse_statement().unwrap_or_else(|| {
-            let next_expression = self.parse_expression();
-            let next_expression_span = *next_expression.span();
-            self.arena
-                .alloc_node(Statement::Expression(next_expression), next_expression_span)
-        });
-        if statement_needs_semicolon(&next_statement)
-            && let Some((Token::Semicolon, semicolon_position)) = self.peek_token_and_position()
-        {
-            next_statement.span_mut().extend_to(semicolon_position);
+        statements: &mut StatementList<'src, 'arena>,
+    ) -> ParseResult<'src, 'arena, ()> {
+        let mut statement = match self.parse_statement() {
+            Some(statement) => statement,
+            None => {
+                // Non-statement starters are parsed as expression statements
+                self.parse_expression_statement_in_block()?
+            }
+        };
+        if block_item_requires_semicolon(&statement) {
+            match self.peek_token_and_position() {
+                Some((Token::Semicolon, semicolon_position)) => {
+                    statement.span_mut().extend_to(semicolon_position);
                     self.advance(); // ';'
                 }
-        statements.push(next_statement);
-    }
-}
-
-fn statement_needs_semicolon(statement: &Statement) -> bool {
-    use Statement::{Empty, Error, Expression, Function, Label, LocalVariableDeclaration};
-    match statement {
-        Empty | Label(_) | Error | Function(_) => false,
-        Expression(expression) => expression_needs_semicolon(expression),
-        LocalVariableDeclaration { .. } => true,
-    }
-}
-
-const fn expression_needs_semicolon(expression: &Expression) -> bool {
-    use Expression::{Block, DoUntil, Error, For, ForEach, If, Switch, While};
-    matches!(
-        expression,
-        Block { .. }
-            | If { .. }
-            | While { .. }
-            | DoUntil { .. }
-            | ForEach { .. }
-            | For { .. }
-            | Switch { .. }
-            | Error
+                // A final expression before `}` may omit `;`; this makes it
+                // the block's tail value.
+                //
+                // On end-of-file, suppress the missing-`;` diagnostic as well.
+                // The block parser will report the missing `}`,
+                // and an extra semicolon error would just cascade.
+                None | Some((Token::RightBrace, _)) => (),
+                Some((_, unexpected_token_position)) => {
+                    self.make_error_at_last_consumed(
+                        ParseErrorKind::BlockMissingSemicolonAfterExpression,
                     )
+                    .widen_error_span_from(statement.span().start)
+                    .blame_token(unexpected_token_position)
+                    .related("expression_span", *statement.span())
+                    .report(self);
+                }
+            }
+        }
+        statements.push(statement);
+        Ok(())
+    }
+
+    fn parse_expression_statement_in_block(
+        &mut self,
+    ) -> ParseResult<'src, 'arena, StatementRef<'src, 'arena>> {
+        let expression_start_position = self.peek_position_or_eof();
+        let expected_block_item_after_position = self.last_consumed_position_or_start();
+        let expression_result = self.parse_expression_with_start_error(
+            ParseErrorKind::BlockExpectedItem,
+            expected_block_item_after_position,
+            expected_block_item_after_position,
+        );
+        let expression = match expression_result {
+            Ok(expression) => expression,
+            Err(error) => {
+                let expression_recovery_made_no_progress =
+                    self.peek_position_or_eof() == expression_start_position;
+                // Without progress, a fallback statement could leave
+                // the block loop stuck.
+                if expression_recovery_made_no_progress {
+                    return self.recover_bad_block_item_start_as_error_statement(error);
+                }
+                error.fallback(self)
+            }
+        };
+        let expression_span = *expression.span();
+        Ok(self
+            .arena
+            .alloc_node(Statement::Expression(expression), expression_span))
+    }
+
+    fn recover_bad_block_item_start_as_error_statement(
+        &mut self,
+        error: crate::parser::ParseError,
+    ) -> ParseResult<'src, 'arena, StatementRef<'src, 'arena>> {
+        let position_before_statement_recovery = self.peek_position_or_eof();
+        // Recover one damaged block item if possible;
+        // otherwise let the enclosing block recover at its own boundary.
+        let error = error.sync_error_at(self, SyncLevel::StatementTerminator);
+        if self.peek_position_or_eof() != position_before_statement_recovery {
+            return Ok(error.fallback(self));
+        }
+        Err(error)
+    }
+}
+
+fn block_item_requires_semicolon(statement: &Statement) -> bool {
+    // Control-flow and block expressions do not require a trailing semicolon
+    // when used as block items.
+    if let Statement::Expression(expression) = statement {
+        !matches!(
+            **expression,
+            Expression::Block { .. }
+                | Expression::If { .. }
+                | Expression::While { .. }
+                | Expression::DoUntil { .. }
+                | Expression::ForEach { .. }
+                | Expression::For { .. }
+                | Expression::Switch { .. }
+                | Expression::Error
+        )
+    } else {
+        false
+    }
 }

rottlib/src/parser/grammar/expression/control_flow/for_loop.rs

@@ -122,6 +122,8 @@ impl<'src, 'arena> Parser<'src, 'arena> {
                 )
                 // Header recovery must not consume the next `;`;
                 // it belongs to the surrounding `for` header.
+                // That's why `SyncLevel` match is preferable to syncing onto
+                // matching delimiter - latter wouldn't stop at preceding `;`.
                 .sync_error_until(self, SyncLevel::CloseParenthesis)
                 .unwrap_or_fallback(self),
             )
@@ -216,7 +218,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
             )
             .widen_error_span_from(for_keyword_position)
             .related_token("for_header_start", left_parenthesis_position)
-            .sync_error_at(self, SyncLevel::CloseParenthesis)
+            .sync_error_at_matching_delimiter(self, left_parenthesis_position)
             .ok_or_report(self);
     }
 

rottlib/src/parser/grammar/expression/control_flow/mod.rs

@@ -97,27 +97,13 @@ impl<'src, 'arena> Parser<'src, 'arena> {
         else {
             return None;
         };
-        let mut nesting_depth: usize = 1;
-        let mut lookahead_token_offset: usize = 1;
-        while let Some(lookahead_token) = self.peek_token_at(lookahead_token_offset) {
-            match lookahead_token {
-                Token::LeftParenthesis => nesting_depth += 1,
-                Token::RightParenthesis => {
-                    if nesting_depth == 1 {
-                        return self
-                            .peek_token_at(lookahead_token_offset + 1)
+
+        let right_parenthesis_position =
+            self.file().matching_delimiter(left_parenthesis_position)?;
+
+        self.peek_token_after_position(right_parenthesis_position)
             .is_some_and(|token| token.is_valid_identifier_name())
-                            .then_some(left_parenthesis_position);
-                    }
-                    nesting_depth -= 1;
-                }
-                _ => (),
-            }
-            lookahead_token_offset += 1;
-        }
-        // Recovery is left to normal expression parsing when the closing `)`
-        // is missing.
-        None
+            .then_some(left_parenthesis_position)
     }
 
     /// Parses a control-flow condition.

rottlib/src/parser/grammar/expression/primary/mod.rs

@@ -78,7 +78,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
                 token_position,
             ),
             Token::LeftParenthesis => self.parse_parenthesized_expression_tail(token_position),
-            Token::LeftBrace => self.parse_block_tail(token_position),
+            Token::LeftBrace => self.parse_block_body_tail(token_position),
             Token::Keyword(keyword) => {
                 match self.try_parse_keyword_primary(keyword, token_position) {
                     Some(keyword_expression) => keyword_expression,
@@ -196,7 +196,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
                 .widen_error_span_from(left_parenthesis_position)
                 .extend_blame_to_next_token(self)
                 .related_token("left_parenthesis", left_parenthesis_position)
-                .sync_error_until(self, SyncLevel::CloseParenthesis)
+                .sync_error_at_matching_delimiter(self, left_parenthesis_position)
                 .fallback(self);
         };
         let inner_expression = self.parse_expression();
@@ -206,7 +206,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
                 ParseErrorKind::ParenthesizedExpressionMissingClosingParenthesis,
             )
             .widen_error_span_from(left_parenthesis_position)
-            .sync_error_at(self, SyncLevel::CloseParenthesis)
+            .sync_error_at_matching_delimiter(self, left_parenthesis_position)
             .extend_blame_start_to_covered_start()
             .related_token("left_parenthesis", left_parenthesis_position)
             .unwrap_or_fallback(self);

rottlib/src/parser/grammar/expression/primary/new.rs

@@ -277,7 +277,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
                 error = error.related("first_extra_argument", span);
             }
             error
-                .sync_error_until(self, SyncLevel::CloseParenthesis)
+                .sync_error_until_matching_delimiter(self, state.left_parenthesis_position)
                 .report_error(self);
         }
     }
@@ -296,7 +296,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
             .related_token("new_keyword", state.new_keyword_position)
             .related_token("left_parenthesis", state.left_parenthesis_position);
         let class_specifier_parse_action = if self.next_token_definitely_cannot_start_expression() {
-            error = error.sync_error_at(self, SyncLevel::CloseParenthesis);
+            error = error.sync_error_at_matching_delimiter(self, state.left_parenthesis_position);
             // Skipping the class specifier avoids cascading errors when
             // the next token cannot start an expression anyway.
             NewClassSpecifierParseAction::Skip

rottlib/src/parser/grammar/expression/switch.rs

@@ -96,7 +96,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
             // at statement sync level.
             self.expect(Token::Colon, ParseErrorKind::SwitchCaseMissingColon)
                 .widen_error_span_from(case_position)
-                .sync_error_until(self, crate::parser::SyncLevel::Statement)
+                .sync_error_until(self, crate::parser::SyncLevel::StatementStart)
                 .report_error(self);
         }
         let mut body = self.arena.vec();
@@ -115,7 +115,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
         self.advance(); // 'default'
         self.expect(Token::Colon, ParseErrorKind::SwitchCaseMissingColon)
             .widen_error_span_from(default_position)
-            .sync_error_until(self, crate::parser::SyncLevel::Statement)
+            .sync_error_until(self, crate::parser::SyncLevel::StatementStart)
             .report_error(self);
         self.parse_switch_arm_body(statements);
     }
@@ -129,7 +129,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
             match token {
                 Token::Keyword(Keyword::Case | Keyword::Default) | Token::RightBrace => break,
                 _ => {
-                    self.parse_next_block_item_into(statements);
+                    self.parse_and_append_next_block_item(statements);
                     self.ensure_forward_progress(token_position);
                 }
             }

rottlib/src/parser/grammar/statement.rs

@@ -11,8 +11,9 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
     /// Parses a single statement.
     ///
     /// Does not consume a trailing `;` except for [`Statement::Empty`].
-    /// The caller handles semicolons. Returns [`Some`] if a statement is
+    /// The caller handles semicolons (WRONG NOW - WE MUST HANDLE THEM). Returns [`Some`] if a statement is
     /// recognized; otherwise [`None`].
+    /// ALSO WE SPECIFICALLY DONT HANDLE EXPRESSION TYPE STATEMENTS
     #[must_use]
     pub(crate) fn parse_statement(&mut self) -> Option<StatementRef<'src, 'arena>> {
         let Some((token, lexeme, position)) = self.peek_token_lexeme_and_position() else {

rottlib/src/parser/recovery.rs

@@ -50,7 +50,10 @@ pub enum SyncLevel {
     ///
     /// Includes `;` and keywords that begin standalone statements /
     /// statement-like control-flow forms.
-    Statement,
+    StatementStart,
+
+    /// Statement terminator `;`.
+    StatementTerminator,
 
     /// Start of a `switch` arm.
     ///
@@ -77,7 +80,7 @@ impl SyncLevel {
         use crate::lexer::Keyword;
         use SyncLevel::{
             BlockBoundary, CloseAngleBracket, CloseBracket, CloseParenthesis, DeclarationStart,
-            ExpressionStart, ListSeparator, Statement, SwitchArmStart,
+            ExpressionStart, ListSeparator, StatementStart, StatementTerminator, SwitchArmStart,
         };
 
         match token {
@@ -88,8 +91,7 @@ impl SyncLevel {
             Token::RightBracket => Some(CloseBracket),
 
             // Statement-level boundaries
-            Token::Semicolon
-            | Token::Keyword(
+            Token::Keyword(
                 Keyword::If
                 | Keyword::Else
                 | Keyword::Switch
@@ -102,7 +104,9 @@ impl SyncLevel {
                 | Keyword::Break
                 | Keyword::Continue
                 | Keyword::Local,
-            ) => Some(Statement),
+            ) => Some(StatementStart),
+
+            Token::Semicolon => Some(StatementTerminator),
 
             // Switch-specific stronger boundary
             Token::Keyword(Keyword::Case | Keyword::Default) => Some(SwitchArmStart),
@@ -138,6 +142,22 @@ impl SyncLevel {
             }
         }
     }
+
+    fn fallback_sync_level_for_delimiter_start(token: Option<Token>) -> SyncLevel {
+        match token {
+            Some(Token::LeftParenthesis) => SyncLevel::CloseParenthesis,
+            Some(Token::LeftBracket) => SyncLevel::CloseBracket,
+            Some(Token::LeftBrace) => SyncLevel::BlockBoundary,
+            _ => SyncLevel::CloseParenthesis,
+        }
+    }
+
+    fn is_opening_delimiter(token: Token) -> bool {
+        matches!(
+            token,
+            Token::LeftParenthesis | Token::LeftBracket | Token::LeftBrace
+        )
+    }
 }
 
 impl<'src, 'arena> Parser<'src, 'arena> {
@@ -171,6 +191,105 @@ impl<'src, 'arena> Parser<'src, 'arena> {
         }
     }
 
+    /// Skips tokens until a token with exactly `level` is found, then consumes
+    /// that token.
+    ///
+    /// This mirrors the behavior used by [`ResultRecoveryExt::sync_error_at`]:
+    /// stronger sync tokens can stop [`Self::recover_until`], but they are not
+    /// consumed unless they are exactly the requested level.
+    fn recover_at_sync_level(&mut self, level: SyncLevel) {
+        self.recover_until(level);
+
+        if self
+            .peek_token()
+            .and_then(SyncLevel::for_token)
+            .is_some_and(|next_level| next_level == level)
+        {
+            self.advance();
+        }
+    }
+
+    /// Recovers up to the lexer-produced matching delimiter for
+    /// `delimiter_start`, if possible, but does not consume it.
+    ///
+    /// If `delimiter_start` is not an opening delimiter, if no match is known,
+    /// or if the parser has already moved past the matching delimiter, this
+    /// falls back to ordinary sync-level recovery inferred from
+    /// `delimiter_start`.
+    pub(crate) fn recover_until_matching_delimiter_or_sync(
+        &mut self,
+        delimiter_start: TokenPosition,
+    ) {
+        let start_token = self.file().token_at(delimiter_start).map(|data| data.token);
+        let fallback_level = SyncLevel::fallback_sync_level_for_delimiter_start(start_token);
+
+        let Some(start_token) = start_token else {
+            self.recover_until(fallback_level);
+            return;
+        };
+
+        if !SyncLevel::is_opening_delimiter(start_token) {
+            self.recover_until(fallback_level);
+            return;
+        }
+
+        let Some(target) = self.file().matching_delimiter(delimiter_start) else {
+            self.recover_until(fallback_level);
+            return;
+        };
+
+        if self.peek_position_or_eof() > target {
+            self.recover_until(fallback_level);
+            return;
+        }
+
+        while self.peek_position_or_eof() < target {
+            self.advance();
+        }
+    }
+
+    /// Recovers by using the lexer-produced matching delimiter for
+    /// `delimiter_start`, if possible.
+    ///
+    /// If `delimiter_start` is not an opening delimiter, if no match is known,
+    /// or if the parser has already moved past the matching delimiter, this
+    /// falls back to ordinary sync-level recovery inferred from
+    /// `delimiter_start`.
+    pub(crate) fn recover_at_matching_delimiter_or_sync(&mut self, delimiter_start: TokenPosition) {
+        let start_token = self.file().token_at(delimiter_start).map(|data| data.token);
+        let fallback_level = SyncLevel::fallback_sync_level_for_delimiter_start(start_token);
+
+        let Some(start_token) = start_token else {
+            self.recover_at_sync_level(fallback_level);
+            return;
+        };
+
+        if !SyncLevel::is_opening_delimiter(start_token) {
+            self.recover_at_sync_level(fallback_level);
+            return;
+        }
+
+        let Some(target) = self.file().matching_delimiter(delimiter_start) else {
+            self.recover_at_sync_level(fallback_level);
+            return;
+        };
+
+        if self.peek_position_or_eof() > target {
+            self.recover_at_sync_level(fallback_level);
+            return;
+        }
+
+        while self.peek_position_or_eof() < target {
+            self.advance();
+        }
+
+        if self.peek_position_or_eof() == target {
+            self.advance();
+        } else {
+            self.recover_at_sync_level(fallback_level);
+        }
+    }
+
     /// Reports `error` and returns the recovery fallback for `T`.
     ///
     /// This is the primitive used when parsing must keep going with a
@@ -234,6 +353,39 @@ pub trait ResultRecoveryExt<'src, 'arena, T>: Sized {
     #[must_use]
     fn sync_error_at(self, parser: &mut Parser<'src, 'arena>, level: SyncLevel) -> Self;
 
+    /// Extends the right end of the error span up to, but not including, the
+    /// known matching closing delimiter for `delimiter_start`, if that delimiter
+    /// is known and has not already been passed.
+    ///
+    /// If no usable delimiter match exists, falls back to ordinary
+    /// [`SyncLevel`]-based recovery. The fallback level is inferred from the
+    /// token at `delimiter_start`.
+    #[must_use]
+    fn sync_error_until_matching_delimiter(
+        self,
+        parser: &mut Parser<'src, 'arena>,
+        delimiter_start: TokenPosition,
+    ) -> Self;
+
+    /// Extends the right end of the error span to include the known matching
+    /// closing delimiter for `delimiter_start`, if that delimiter is known and
+    /// has not already been passed.
+    ///
+    /// If no usable delimiter match exists, falls back to ordinary
+    /// [`SyncLevel`]-based recovery. The fallback level is inferred from the
+    /// token at `delimiter_start`:
+    ///
+    /// - `(` -> [`SyncLevel::CloseParenthesis`]
+    /// - `[` -> [`SyncLevel::CloseBracket`]
+    /// - `{` -> [`SyncLevel::BlockBoundary`]
+    /// - anything else -> [`SyncLevel::CloseParenthesis`]
+    #[must_use]
+    fn sync_error_at_matching_delimiter(
+        self,
+        parser: &mut Parser<'src, 'arena>,
+        delimiter_start: TokenPosition,
+    ) -> Self;
+
     /// Either returns expected value or its best effort fallback.
     #[must_use]
     fn unwrap_or_fallback(self, parser: &mut Parser<'src, 'arena>) -> T
@@ -305,6 +457,36 @@ impl<'src, 'arena, T> ResultRecoveryExt<'src, 'arena, T> for ParseResult<'src, '
         self
     }
 
+    fn sync_error_until_matching_delimiter(
+        mut self,
+        parser: &mut Parser<'src, 'arena>,
+        delimiter_start: TokenPosition,
+    ) -> Self {
+        if let Err(ref mut error) = self {
+            parser.recover_until_matching_delimiter_or_sync(delimiter_start);
+            error.covered_span.end = std::cmp::max(
+                error.covered_span.end,
+                parser.last_consumed_position_or_start(),
+            );
+        }
+        self
+    }
+
+    fn sync_error_at_matching_delimiter(
+        mut self,
+        parser: &mut Parser<'src, 'arena>,
+        delimiter_start: TokenPosition,
+    ) -> Self {
+        if let Err(ref mut error) = self {
+            parser.recover_at_matching_delimiter_or_sync(delimiter_start);
+            error.covered_span.end = std::cmp::max(
+                error.covered_span.end,
+                parser.last_consumed_position_or_start(),
+            );
+        }
+        self
+    }
+
     fn unwrap_or_fallback(self, parser: &mut Parser<'src, 'arena>) -> T
     where
         T: RecoveryFallback<'src, 'arena>,
@@ -390,6 +572,32 @@ impl<'src, 'arena> ResultRecoveryExt<'src, 'arena, ()> for ParseError {
         self
     }
 
+    fn sync_error_until_matching_delimiter(
+        mut self,
+        parser: &mut Parser<'src, 'arena>,
+        delimiter_start: TokenPosition,
+    ) -> Self {
+        parser.recover_until_matching_delimiter_or_sync(delimiter_start);
+        self.covered_span.end = std::cmp::max(
+            self.covered_span.end,
+            parser.last_consumed_position_or_start(),
+        );
+        self
+    }
+
+    fn sync_error_at_matching_delimiter(
+        mut self,
+        parser: &mut Parser<'src, 'arena>,
+        delimiter_start: TokenPosition,
+    ) -> Self {
+        parser.recover_at_matching_delimiter_or_sync(delimiter_start);
+        self.covered_span.end = std::cmp::max(
+            self.covered_span.end,
+            parser.last_consumed_position_or_start(),
+        );
+        self
+    }
+
     fn unwrap_or_fallback(self, parser: &mut Parser<'src, 'arena>) {
         parser.report_error(self);
     }

rottlib/tests/lexer_diagnostics.rs

@@ -0,0 +1,350 @@
+use std::collections::HashMap;
+
+use rottlib::diagnostics::{Diagnostic, Severity};
+use rottlib::lexer::{TokenPosition, TokenSpan, TokenizedFile};
+
+#[derive(Debug)]
+struct ExpectedLabel {
+    span: TokenSpan,
+    message: &'static str,
+}
+
+#[derive(Debug)]
+struct ExpectedDiagnostic<'a> {
+    headline: &'static str,
+    severity: Severity,
+    code: Option<&'static str>,
+    primary_label: Option<ExpectedLabel>,
+    secondary_labels: &'a [ExpectedLabel],
+    help: Option<&'static str>,
+    notes: &'a [&'static str],
+}
+
+#[track_caller]
+fn assert_diagnostic(actual: &Diagnostic, expected: &ExpectedDiagnostic<'_>) {
+    assert_eq!(actual.headline(), expected.headline);
+    assert_eq!(actual.severity(), expected.severity);
+    assert_eq!(actual.code(), expected.code);
+    assert_eq!(actual.help(), expected.help);
+
+    match (actual.primary_label(), expected.primary_label.as_ref()) {
+        (None, None) => {}
+        (Some(actual), Some(expected)) => {
+            assert_eq!(actual.span, expected.span);
+            assert_eq!(actual.message, expected.message);
+        }
+        _ => panic!("primary label mismatch"),
+    }
+
+    let actual_secondary = actual.secondary_labels();
+    assert_eq!(actual_secondary.len(), expected.secondary_labels.len());
+
+    for (actual, expected) in actual_secondary
+        .iter()
+        .zip(expected.secondary_labels.iter())
+    {
+        assert_eq!(actual.span, expected.span);
+        assert_eq!(actual.message, expected.message);
+    }
+
+    let actual_notes = actual.notes();
+    assert_eq!(actual_notes.len(), expected.notes.len());
+
+    for (actual, expected) in actual_notes.iter().zip(expected.notes.iter()) {
+        assert_eq!(actual, expected);
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+struct Fixture {
+    label: &'static str,
+    source: &'static str,
+}
+
+type FixtureRun = Vec<Diagnostic>;
+
+struct FixtureRuns {
+    runs: HashMap<&'static str, FixtureRun>,
+}
+
+impl FixtureRuns {
+    #[track_caller]
+    fn get(&self, label: &str) -> Option<Vec<Diagnostic>> {
+        self.runs.get(label).cloned()
+    }
+
+    #[track_caller]
+    fn get_any(&self, label: &str) -> Diagnostic {
+        self.runs
+            .get(label)
+            .map(|fixture_run| fixture_run[0].clone())
+            .unwrap_or_else(|| panic!("no fixture run for `{label}`"))
+    }
+
+    #[track_caller]
+    fn get_by_code(&self, label: &str, code: &str) -> Diagnostic {
+        self.runs
+            .get(label)
+            .unwrap_or_else(|| panic!("no fixture run for `{label}`"))
+            .iter()
+            .find(|diagnostic| diagnostic.code() == Some(code))
+            .unwrap_or_else(|| panic!("no `{code}` diagnostic in fixture `{label}`"))
+            .clone()
+    }
+}
+
+const fn span(position: usize) -> TokenSpan {
+    TokenSpan {
+        start: TokenPosition(position),
+        end: TokenPosition(position),
+    }
+}
+
+const LEXER_FIXTURES: &[Fixture] = &[
+    Fixture {
+        label: "files/L0001_01.uc",
+        source: "`",
+    },
+    Fixture {
+        label: "files/L0002_01.uc",
+        source: "]",
+    },
+    Fixture {
+        label: "files/L0003_01.uc",
+        source: "{\n    foo(\n}\n",
+    },
+    Fixture {
+        label: "files/L0004_01.uc",
+        source: "(]",
+    },
+    Fixture {
+        label: "files/L0005_01.uc",
+        source: "foo(",
+    },
+    Fixture {
+        label: "files/L_mixed_01.uc",
+        source: "([)]",
+    },
+];
+
+fn run_fixture(fixture: &'static Fixture) -> FixtureRun {
+    let file = TokenizedFile::tokenize(fixture.source);
+    file.diagnostics().to_vec()
+}
+
+fn run_fixtures(fixtures: &'static [Fixture]) -> FixtureRuns {
+    let mut runs = HashMap::new();
+
+    for fixture in fixtures {
+        runs.insert(fixture.label, run_fixture(fixture));
+    }
+
+    FixtureRuns { runs }
+}
+
+#[test]
+fn check_lexer_diagnostic_counts() {
+    let runs = run_fixtures(LEXER_FIXTURES);
+
+    assert_eq!(runs.get("files/L0001_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/L0002_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/L0003_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/L0004_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/L0005_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/L_mixed_01.uc").unwrap().len(), 2);
+}
+
+#[test]
+fn check_l0001_invalid_token() {
+    let runs = run_fixtures(LEXER_FIXTURES);
+
+    assert_diagnostic(
+        &runs.get_any("files/L0001_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "invalid token: backtick",
+            severity: Severity::Error,
+            code: Some("L0001"),
+            primary_label: Some(ExpectedLabel {
+                span: span(0),
+                message: "invalid token: backtick",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_l0002_unexpected_closing_delimiter() {
+    let runs = run_fixtures(LEXER_FIXTURES);
+
+    assert_diagnostic(
+        &runs.get_any("files/L0002_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "unexpected closing delimiter: `]`",
+            severity: Severity::Error,
+            code: Some("L0002"),
+            primary_label: Some(ExpectedLabel {
+                span: span(0),
+                message: "unexpected closing delimiter",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_l0003_unclosed_delimiter_before_later_close() {
+    let runs = run_fixtures(LEXER_FIXTURES);
+
+    assert_diagnostic(
+        &runs.get_any("files/L0003_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "unclosed delimiter before `}`",
+            severity: Severity::Error,
+            code: Some("L0003"),
+            primary_label: Some(ExpectedLabel {
+                span: span(4),
+                message: "this `(` is not closed before `}`",
+            }),
+            secondary_labels: &[
+                ExpectedLabel {
+                    span: span(6),
+                    message: "this `}` is matched with the earlier `{`",
+                },
+                ExpectedLabel {
+                    span: span(0),
+                    message: "this `{` is likely the intended match",
+                },
+            ],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_l0004_mismatched_closing_delimiter() {
+    let runs = run_fixtures(LEXER_FIXTURES);
+
+    assert_diagnostic(
+        &runs.get_any("files/L0004_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "mismatched closing delimiter: `]`",
+            severity: Severity::Error,
+            code: Some("L0004"),
+            primary_label: Some(ExpectedLabel {
+                span: span(1),
+                message: "closing delimiter does not match `(`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: span(0),
+                message: "`(` opened here",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_l0005_unclosed_delimiter_at_eof() {
+    let runs = run_fixtures(LEXER_FIXTURES);
+
+    assert_diagnostic(
+        &runs.get_any("files/L0005_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "unclosed delimiter: `(`",
+            severity: Severity::Error,
+            code: Some("L0005"),
+            primary_label: Some(ExpectedLabel {
+                span: span(1),
+                message: "this `(` was never closed",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_mixed_recovery_diagnostics() {
+    let runs = run_fixtures(LEXER_FIXTURES);
+
+    assert_diagnostic(
+        &runs.get_by_code("files/L_mixed_01.uc", "L0003"),
+        &ExpectedDiagnostic {
+            headline: "unclosed delimiter before `)`",
+            severity: Severity::Error,
+            code: Some("L0003"),
+            primary_label: Some(ExpectedLabel {
+                span: span(1),
+                message: "this `[` is not closed before `)`",
+            }),
+            secondary_labels: &[
+                ExpectedLabel {
+                    span: span(2),
+                    message: "this `)` is matched with the earlier `(`",
+                },
+                ExpectedLabel {
+                    span: span(0),
+                    message: "this `(` is likely the intended match",
+                },
+            ],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_by_code("files/L_mixed_01.uc", "L0002"),
+        &ExpectedDiagnostic {
+            headline: "unexpected closing delimiter: `]`",
+            severity: Severity::Error,
+            code: Some("L0002"),
+            primary_label: Some(ExpectedLabel {
+                span: span(3),
+                message: "unexpected closing delimiter",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_recovered_delimiter_matches_are_stored() {
+    let file = TokenizedFile::tokenize("{\n    foo(\n}\n");
+
+    assert_eq!(
+        file.matching_delimiter(TokenPosition(0)),
+        Some(TokenPosition(6))
+    );
+    assert_eq!(
+        file.matching_delimiter(TokenPosition(6)),
+        Some(TokenPosition(0))
+    );
+    assert_eq!(file.matching_delimiter(TokenPosition(4)), None);
+}
+
+#[test]
+fn check_mixed_recovery_delimiter_matches_are_stored() {
+    let file = TokenizedFile::tokenize("([)]");
+
+    assert_eq!(
+        file.matching_delimiter(TokenPosition(0)),
+        Some(TokenPosition(2))
+    );
+    assert_eq!(
+        file.matching_delimiter(TokenPosition(2)),
+        Some(TokenPosition(0))
+    );
+
+    assert_eq!(file.matching_delimiter(TokenPosition(1)), None);
+    assert_eq!(file.matching_delimiter(TokenPosition(3)), None);
+}

rottlib/tests/parser_diagnostics/block_items.rs

@@ -0,0 +1,455 @@
+use super::*;
+
+pub(super) const P0025_FIXTURES: &[Fixture] = &[
+    Fixture {
+        label: "files/P0025_01.uc",
+        source: "{\n    local int Count;\n    Count = Count + 1 UpdateHud();\n    DrawHud(CanvasRef);\n}\n",
+    },
+    Fixture {
+        label: "files/P0025_02.uc",
+        source: "{\n    local float XL;\n    C.TextSize(LevelTitle, XL, YL)\n    C.SetPos(0, 0);\n    C.DrawText(LevelTitle);\n}\n",
+    },
+    Fixture {
+        label: "files/P0025_03.uc",
+        source: "{\n    local bool bReady;\n    bReady = CheckReady()\n    if (bReady) { StartMatch(); }\n    NotifyReady();\n}\n",
+    },
+    Fixture {
+        label: "files/P0025_04.uc",
+        source: "{\n    local int I;\n    Scores[I] = Scores[I] + 1\n    I++;\n    RefreshScores();\n}\n",
+    },
+];
+
+pub(super) const P0026_FIXTURES: &[Fixture] = &[
+    Fixture {
+        label: "files/P0026_01.uc",
+        source: "{\n    local int Count;\n    Count = 0;\n    Count++;\n    UpdateHud();\n",
+    },
+    Fixture {
+        label: "files/P0026_02.uc",
+        source: "{\n    local bool bReady;\n    bReady = CheckReady();\n    if (bReady) { StartMatch(); }\n    NotifyReady();\n",
+    },
+    Fixture {
+        label: "files/P0026_03.uc",
+        source: "{    local float XL;    do { C.TextSize(LevelTitle, XL, YL); } until (XL < C.ClipX)    C.SetPos(0, 0);    C.DrawText(LevelTitle);",
+    },
+    Fixture {
+        label: "files/P0026_04.uc",
+        source: "{\n    local int Count;\n    Count = Count + 1;\n    UpdateHud();\n    Count\n",
+    },
+];
+
+pub(super) const P0025_P0026_MIXED_FIXTURES: &[Fixture] = &[
+    Fixture {
+        label: "files/P_mixed_01.uc",
+        source: "{    local int Count;    Count = Count + 1    UpdateHud();    DrawHud(CanvasRef);",
+    },
+    Fixture {
+        label: "files/P_mixed_02.uc",
+        source: "{\n    local bool bReady;\n    bReady = CheckReady()\n    if (bReady) { StartMatch(); }\n    NotifyReady();\n",
+    },
+];
+
+#[test]
+fn check_p0025_fixtures() {
+    let runs = run_fixtures(P0025_FIXTURES);
+
+    assert_eq!(runs.get("files/P0025_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0025_02.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0025_03.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0025_04.uc").unwrap().len(), 1);
+
+    assert_diagnostic(
+        &runs.get_any("files/P0025_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(21),
+                    end: TokenPosition(21),
+                },
+                message: "expected `;` before `UpdateHud`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(11),
+                    end: TokenPosition(19),
+                },
+                message: "expression statement",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0025_02.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(25),
+                    end: TokenPosition(25),
+                },
+                message: "expected `;` before `C`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(22),
+                    end: TokenPosition(22),
+                },
+                message: "expression statement ends here",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0025_03.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(20),
+                    end: TokenPosition(20),
+                },
+                message: "expected `;` before `if`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(17),
+                    end: TokenPosition(17),
+                },
+                message: "expression statement ends here",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0025_04.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(28),
+                    end: TokenPosition(28),
+                },
+                message: "expected `;` before `I`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(25),
+                    end: TokenPosition(25),
+                },
+                message: "expression statement ends here",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_p0026_fixtures() {
+    let runs = run_fixtures(P0026_FIXTURES);
+
+    assert_eq!(runs.get("files/P0026_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0026_02.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0026_03.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0026_04.uc").unwrap().len(), 1);
+
+    assert_diagnostic(
+        &runs.get_any("files/P0026_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(0),
+                    end: TokenPosition(29),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0026_02.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(0),
+                    end: TokenPosition(42),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0026_03.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(59),
+                    end: TokenPosition(59),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0026_04.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(0),
+                    end: TokenPosition(31),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_p0025_mixed_fixtures() {
+    let runs = run_fixtures(P0025_P0026_MIXED_FIXTURES);
+
+    assert_eq!(runs.get("files/P_mixed_01.uc").unwrap().len(), 2);
+    assert_eq!(runs.get("files/P_mixed_02.uc").unwrap().len(), 2);
+
+    assert_diagnostic(
+        &runs.get_by_code("files/P_mixed_01.uc", "P0025"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(19),
+                    end: TokenPosition(19),
+                },
+                message: "expected `;` before `UpdateHud`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(9),
+                    end: TokenPosition(17),
+                },
+                message: "expression statement",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_by_code("files/P_mixed_02.uc", "P0025"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(20),
+                    end: TokenPosition(20),
+                },
+                message: "expected `;` before `if`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(17),
+                    end: TokenPosition(17),
+                },
+                message: "expression statement ends here",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_p0026_mixed_fixtures() {
+    let runs = run_fixtures(P0025_P0026_MIXED_FIXTURES);
+
+    assert_eq!(runs.get("files/P_mixed_01.uc").unwrap().len(), 2);
+    assert_eq!(runs.get("files/P_mixed_02.uc").unwrap().len(), 2);
+
+    assert_diagnostic(
+        &runs.get_by_code("files/P_mixed_01.uc", "P0026"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(29),
+                    end: TokenPosition(29),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_by_code("files/P_mixed_02.uc", "P0026"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(0),
+                    end: TokenPosition(41),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+pub(super) const P0027_FIXTURES: &[Fixture] = &[
+    Fixture {
+        label: "files/P0027_01.uc",
+        source: "{\n    local bool bReady;\n    bReady = CheckReady();\n    else { StartMatch(); }\n    NotifyReady();\n}\n",
+    },
+    Fixture {
+        label: "files/P0027_02.uc",
+        source: "{    local int Count;    Count = 3;    case 3:        Count++;    UpdateHud();}",
+    },
+    Fixture {
+        label: "files/P0027_03.uc",
+        source: "{\n    local bool bDone;\n    bDone = false;\n    until (bDone)\n    TickWork();\n}\n",
+    },
+    Fixture {
+        label: "files/P0027_04.uc",
+        source: "{\n    local int Count;\n    Count = 0;\n    #exec TEXTURE IMPORT NAME=Bad FILE=Bad.bmp\n    Count++;\n}\n",
+    },
+];
+
+#[test]
+fn check_p0027_fixtures() {
+    let runs = run_fixtures(P0027_FIXTURES);
+
+    assert_eq!(runs.get("files/P0027_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0027_02.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0027_03.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0027_04.uc").unwrap().len(), 1);
+
+    assert_diagnostic(
+        &runs.get_any("files/P0027_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "expected statement or expression, found `else`",
+            severity: Severity::Error,
+            code: Some("P0027"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(21),
+                    end: TokenPosition(21),
+                },
+                message: "unexpected `else`",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0027_02.uc"),
+        &ExpectedDiagnostic {
+            headline: "expected statement or expression, found `case`",
+            severity: Severity::Error,
+            code: Some("P0027"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(16),
+                    end: TokenPosition(16),
+                },
+                message: "unexpected `case`",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0027_03.uc"),
+        &ExpectedDiagnostic {
+            headline: "expected statement or expression, found `until`",
+            severity: Severity::Error,
+            code: Some("P0027"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(19),
+                    end: TokenPosition(19),
+                },
+                message: "unexpected `until`",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0027_04.uc"),
+        &ExpectedDiagnostic {
+            headline: "expected statement or expression, found `#exec` directive",
+            severity: Severity::Error,
+            code: Some("P0027"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(19),
+                    end: TokenPosition(19),
+                },
+                message: "`#exec` directives are not allowed in a statement block",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}

rottlib/tests/parser_diagnostics/mod.rs

@@ -5,6 +5,7 @@ use rottlib::diagnostics::{Diagnostic, Severity};
 use rottlib::lexer::{TokenPosition, TokenSpan, TokenizedFile};
 use rottlib::parser::Parser;
 
+mod block_items;
 mod control_flow_expressions;
 mod primary_expressions;