Crate antlr_rust

Antlr4 runtime

This is pre-release version. Some small breaking changes are still possible, although none is currently planned

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:

• ANTLR4 main repository
• README for Rust target

Customization

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:

• CharStream - Lexer input, stream of char values with slicing support
• TokenFactory - How lexer creates tokens.
• Token - Element of TokenStream
• TokenStream - Parser input, created from lexer or other token source.
• ParserRuleContext - Node of created syntax tree.

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. Besides reference 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 return 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

Downcasting

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.

Modules

atn_config
atn_simulator
char_stream
common_token_stream
error_listener
error_strategy
errors
int_stream
interval_set
lexer
lexer_atn_simulator
parser
parser_atn_simulator
parser_rule_context
prediction_mode
recognizer
rule_context
token
token_factory
token_source
token_stream
tree
trees	A set of utility routines useful for all kinds of ANTLR trees.
vocabulary

Structs

BailErrorStrategy	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.
BaseLexer
BaseParser	Main underlying Parser struct
DefaultErrorStrategy
InputStream	Default rust target input stream.
ListenerId	Allows to safely cast listener back to user type
PredictionContextCache

Traits

ErrorStrategy	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
Parser