Enum nom::Err

pub enum Err<I, E = u32> {
    Incomplete(Needed),
    Error(Context<I, E>),
    Failure(Context<I, E>),
}

The Err enum indicates the parser was not successful

It has three cases:

• Incomplete indicates that more data is needed to decide. The Needed enum can contain how many additional bytes are necessary. If you are sure your parser is working on full data, you can wrap your parser with the complete combinator to transform that case in Error
• Error means some parser did not succeed, but another one might (as an example, when testing different branches of an alt combinator)
• Failure indicates an unrecoverable error. As an example, if you recognize a prefix to decide on the next parser to apply, and that parser fails, you know there's no need to try other parsers, you were already in the right branch, so the data is invalid

Depending on a compilation flag, the content of the Context enum can change. In the default case, it will only have one variant: Context::Code(I, ErrorKind<E=u32>) (with I and E configurable). It contains an error code and the input position that triggered it.

If you activate the verbose-errors compilation flags, it will add another variant to the enum: Context::List(Vec<(I, ErrorKind<E>)>). This variant aggregates positions and error codes as the code backtracks through the nested parsers. The verbose errors feature allows for very flexible error management: you can know precisely which parser got to which part of the input. The main drawback is that it is a lot slower than default error management.

Variants

Incomplete(Needed)

There was not enough data

Error(Context<I, E>)

The parser had an error (recoverable)

Failure(Context<I, E>)

The parser had an unrecoverable error: we got to the right branch and we know other branches won't work, so backtrack as fast as possible

Methods

impl<I, E> Err<I, E>

pub fn into_error_kind(self) -> ErrorKind<E>

pub fn is_incomplete(&self) -> bool

Trait Implementations

impl<I, H: From<I>, F, E: From<F>> Convert<Err<I, F>> for Err<H, E>

fn convert(e: Err<I, F>) -> Self

impl<I: PartialEq, E: PartialEq> PartialEq<Err<I, E>> for Err<I, E>

fn eq(&self, other: &Err<I, E>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Err<I, E>) -> bool

This method tests for !=.

impl<I: Clone, E: Clone> Clone for Err<I, E>

fn clone(&self) -> Err<I, E>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<I, E> Display for Err<I, E> where     I: Debug,     E: Debug,

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<I: Debug, E: Debug> Debug for Err<I, E>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<I, E> Error for Err<I, E> where     I: Debug,     E: Debug,

fn description(&self) -> &str

This method is soft-deprecated.

fn cause(&self) -> Option<&dyn Error>

Deprecating in 1.33.0

: replaced by Error::source, which can support downcasting

The lower-level cause of this error, if any.

fn source(&self) -> Option<&(dyn Error + 'static)>

The lower-level source of this error, if any.