Module winnow::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 PResult 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:

• ()
• ErrorKind
• InputError (mostly for testing)
• ContextError
• TreeError (mostly for testing)
• Custom errors

Structs

• ContextError
  Accumulate context while backtracking errors
• InputError
  Capture input on error
• ParseError
  See Parser::parse
• TreeErrorBasestd
  See TreeErrorFrame::Kind, ParserError::append
• TreeErrorContextstd
  See TreeErrorFrame::Context, AddContext::add_context

Enums

• ErrMode
  Add parse error state to ParserErrors
• ErrorKind
  Provide some minor debug context for errors
• Needed
  Contains information on needed data if a parser returned Incomplete
• StrContext
  Additional parse context for ContextError added via Parser::context
• StrContextValue
  See StrContext
• TreeErrorstd
  Trace all error paths, particularly for tests
• TreeErrorFramestd
  See TreeError::Stack

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
• FromRecoverableErrorunstable-recover
  Capture context from when an error was recovered
• ParserError
  The basic Parser trait for errors

Type Aliases

• IResult
  For use with Parser::parse_peek which allows the input stream to be threaded through a parser.
• PResult
  For use with Parser::parse_next