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: many0, 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 IResult alias, rather than Result. finish is provided for top-level parsers to integrate with your application’s error reporting.

Error types include:

• ()
• Error
• VerboseError
• [Custom errors][crate::_topic::error]

Structs

• Error
  Default error type, only contains the error’ location and kind
• VerboseError
  Accumulates error information while backtracking

Enums

• ErrMode
  The Err enum indicates the parser was not successful
• ErrorKind
  Indicates which parser returned an error
• Needed
  Contains information on needed data if a parser returned Incomplete
• VerboseErrorKind
  Error context for VerboseError

Traits

• ContextError
  Used by the context to add custom data to error while backtracking
• ErrorConvert
  Equivalent of From implementation to avoid orphan rules in bits parsers
• FinishIResult
  Extension trait to convert a parser’s IResult to a more manageable type
• FromExternalError
  Create a new error with an external error, from std::str::FromStr
• ParseError
  The basic Parser trait for errors

Functions

• append_errorDeprecated
  Combines an existing error with a new one created from the input position and an ErrorKind. This is useful when backtracking through a parse tree, accumulating error context on the way
• contextDeprecated
  Create a new error from an input position, a static string and an existing error. This is used mainly in the context combinator, to add user friendly information to errors when backtracking through a parse tree
• convert_error
  Transforms a VerboseError into a trace with input position information
• dbg_dmpDeprecated
  Prints a message and the input if the parser fails.
• make_errorDeprecated
  Creates an error from the input position and an ErrorKind

Type Definitions

• IResult
  Holds the result of Parser