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Parser Errors (LTX::PARSER::E001-E006)

The parser analyzes the token stream produced by the lexer and constructs an Abstract Syntax Tree (AST) according to the language grammar. This section lists all parser-related errors, their causes, and recommended fixes.

Error Reference Table

CodeVariantDiagnostic MessageRemediation
LTX::PARSER::E001ExpectedTokenExpected token not foundCheck the syntax near the highlighted position — a token is missing or misplaced.
LTX::PARSER::E002UnexpectedEOFUnexpected end of fileClose the construct with its matching delimiter before the file end.
LTX::PARSER::E003UnclosedEnvironmentEnvironment was not closedAdd a matching \end{...} for every \begin{...}.
LTX::PARSER::E004MismatchedEnvironmentEnvironment closing tag mismatchEnsure \end{...} matches the corresponding \begin{...} name.
LTX::PARSER::E005MissingClosingBraceMissing closing braceAdd the matching closing brace } to terminate the group.
LTX::PARSER::E006UnexpectedEOFWhileParsingEnd of file reached while parsing a structureEnsure required structures (e.g. \begin{document}) are present.

Error Categories

Token Errors (LTX::PARSER::E001-E002)

LTX::PARSER::E001 - ExpectedToken

The parser expected a specific token — such as {, }, or an environment — but found something else or reached the end of the stream.

% ❌ Incorrect (missing closing brace)
\newcommand{\foo}{Hello

% ✅ Correct
\newcommand{\foo}{Hello}

LTX::PARSER::E002 - UnexpectedEOF

A construct being parsed (for example inline math) ran to the end of the file without its closing delimiter.

% ❌ Incorrect
A sentence with $x + y = z$

% ✅ Correct
A sentence with $x + y = z$.

Environment Errors (LTX::PARSER::E003-E004)

LTX::PARSER::E003 - UnclosedEnvironment

An environment was opened with \begin{...} but never closed with \end{...}.

% ❌ Incorrect
\begin{itemize}
\item First item
\item Second item

% ✅ Correct
\begin{itemize}
\item First item
\item Second item
\end{itemize}

LTX::PARSER::E004 - MismatchedEnvironment

The environment closing tag doesn’t match the opening tag.

% ❌ Incorrect
\begin{itemize}
\item First item
\end{enumerate}

% ✅ Correct
\begin{itemize}
\item First item
\end{itemize}

Group Errors (LTX::PARSER::E005)

LTX::PARSER::E005 - MissingClosingBrace

A braced group { ... reached the end of the token stream without a matching }.

% ❌ Incorrect
\section{Introduction

% ✅ Correct
\section{Introduction}

Document Structure Errors (LTX::PARSER::E006)

LTX::PARSER::E006 - UnexpectedEOFWhileParsing

The top-level document parsing ended before a required structure — such as \begin{document} — was found.

% ❌ Incorrect
\documentclass{article}
Hello world

% ✅ Correct
\documentclass{article}
\begin{document}
Hello world
\end{document}

Diagnostic Example

🔍 Found 1 issue(s):

LTX::PARSER::E004

  × mismatched environment: expected `\end{itemize}`, found `\end{enumerate}`
    ╭─[main.tex:18:1]
 17 │ \begin{itemize}
 18 │ \end{enumerate}
    · ────────┬───────
    ·         ╰── here
 19 │
    ╰────
  help: Environments must be closed with the same name they were opened with.

Best Practices

  1. Always use matching \begin and \end pairs - Keep environments properly nested
  2. Verify command spelling - Use autocompletion or reference documentation
  3. Load required packages - Ensure all necessary packages are imported
  4. Close every brace and argument - Each { needs a matching }
  5. Structure the document correctly - Include \begin{document} after the preamble