Crate antlr_rust[][src]

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Antlr4 runtime

This is a Rust runtime for ANTLR4 parser generator. It is required to use parsers and lexers generated by ANTLR4 parser generator

This documentation refers to particular api used by generated parsers,lexers and syntax trees.

For info on what is ANTLR4 and how to generate parser please refer to:


All input and output can be customized and optimized for particular usecase by implementing related trait. Each of them already has different implementations that should be enough for most cases. For more details see docs for corresponding trait and containing module.

Currently available are:

Zero-copy and lifetimes

This library supports full zero-copy parsing. To allow this 'input lifetime is used everywhere inside to refer to data borrowed by parser/lexer. Besides references to input it also can be TokenFactory if it returns references to tokens. See ArenaFactory as an example of such behavior. It allocates tokens in Arena and returns references.

Using generated parse tree you should be careful to not require longer lifetime after the parsing. If that’s the case you will likely get “does not live long enough” error on the input string, despite actual lifetime conflict is happening much later

If you need to generate owned versions of parse tree or you want simpler usage, you can opt out zero-copy by requiring 'input to be static. In this case it is easier to also use types that contains “owned” in their name or constructor function like OwningTokenFactory or InputStream::new_owned().

Visitors and Listeners

Parse listeners must outlive 'input because they have to be stored inside of the parser. It still allows to retrieve borrowed data from parse tree which should be enough to cover 99% use cases.

ParseTreeWalker can accept listeners with arbitrary lifetime.

Visitors also can have arbitrary lifetime.


Rule context trait object support downcasting even for zero-copy case. Also generic types(currently these are H:ErrorStrategy and I:TokenStream) that you can access in generated parser from embedded actions also can be downcasted to concrete types. To do it TidExt::downcast_* extension methods should be used.


pub use input_stream::InputStream;


IntStream extension for Lexer that allows subslicing of underlying data

Channel based TokenStream

Error reporting

Error handling and recovery

Error types

Input to lexer

<ost generic stream of symbols

Lexer implementation

Implementation of lexer automata(DFA)

Base parser implementation

Base parser implementation

Full parser node

Minimal parser node

Symbols that parser works on

How Lexer should produce tokens

IntStream that produces tokens for Parser

General AST

A set of utility routines useful for all kinds of ANTLR trees.

Mapping from symbol type to its string representation


This implementation of ANTLRErrorStrategy responds to syntax errors by immediately canceling the parse operation with a ParseCancellationException. The implementation ensures that the ParserRuleContext.exception field is set for all parse tree nodes that were not completed prior to encountering the error.

Default implementation of Lexer

Main underlying Parser struct

This is the default implementation of ErrorStrategy used for error reporting and recovery in ANTLR parsers.

Allows to safely cast listener back to user type


This enum defines the prediction modes available in ANTLR 4 along with utility methods for analyzing configuration sets for conflicts and/or ambiguities.


The interface for defining strategies to deal with syntax errors encountered during a parse by ANTLR-generated parsers. We distinguish between three different kinds of errors:

Lexer functionality required by LexerATNSimulator to work properly

parser functionality required for ParserATNSimulator to work

Produces tokens to be used by parser. TokenStream implementations are responsible for buffering tokens for parser lookahead