Module error

Error management

Errors are designed with multiple needs in mind:

• Accumulate more context as the error goes up the parser chain
• Distinguish between recoverable errors, unrecoverable errors, and more data is needed
• Have a very low overhead, as errors are often discarded by the calling parser (examples: repeat, alt)
• Can be modified according to the user’s needs, because some languages need a lot more information
• Help thread-through the stream

To abstract these needs away from the user, generally winnow parsers use the ModalResult alias, rather than Result. Parser::parse is a top-level operation that can help convert to a Result for integrating with your application’s error reporting.

Error types include:

• EmptyError when the reason for failure doesn’t matter
• ContextError
• InputError (mostly for testing)
• [TreeError] (mostly for testing)
• [Custom errors][crate::_topic::error]

Structs

ContextError

Accumulate context while backtracking errors

EmptyError

Track an error occurred without any other StrContext

InputError

Capture input on error

ParseError

See Parser::parse

Enums

ErrMode

Add parse error state to ParserErrors

Needed

Contains information on needed data if a parser returned Incomplete

StrContext

Additional parse context for ContextError added via Parser::context

StrContextValue

See StrContext

Traits

AddContext

Used by Parser::context to add custom data to error while backtracking

ErrorConvert

Equivalent of From implementation to avoid orphan rules in bits parsers

FromExternalError

Create a new error with an external error, from [std::str::FromStr]

ModalError

Manipulate the how parsers respond to this error

ParserError

The basic Parser trait for errors

Type Aliases

ModalResult

Modal error reporting for Parser::parse_next

Result

By default, the error type (E) is ContextError.