Enum Expectation

#[non_exhaustive]
pub enum Expectation<T> {
    Tag(T),
    Char(char),
    Alpha,
    Digit,
    HexDigit,
    OctDigit,
    AlphaNumeric,
    Space,
    Multispace,
    CrLf,
    Eof,
    Something,
}

Enum for generic things that can be expected by nom parsers

Certain nom parsers (think digit1, tag, or space1) are “base level” in the sense that, rather than combining subparsers, they scan for a specific character or specific kind of character. This enum tracks the different kinds of things that can be expected by these base parses.

Printing an expectation via Display will only include the thing that was expected, in a form suitable for being prefixed with “expected” or suffixed with “was expected”.

This enum is non-exhaustive; it is intended to represent everything parse errors where we know specifically what was expected. For instance, take_while cannot create an Expectation, because it can’t meaningfully report what its subparser is expecting.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Tag(T)

A tag was expected.

Char(char)

A specific character was expected.

Alpha

An ASCII letter ([a-zA-Z]) was expected.

Digit

A decimal digit ([0-9]) was expected.

HexDigit

A hexadecimal digit ([0-9a-fA-F]) was expected.

OctDigit

An octal digit ([0-7]) was expected.

AlphaNumeric

An alphanumeric character ([0-9a-zA-Z]) was expected.

Space

A space or tab was expected.

Multispace

A space, tab, newline, or carriage return was expected.

CrLf

"\r\n" was expected.

Eof

Eof was expected.

Something

Expected something; ie, not Eof.

Trait Implementations

impl<T: Clone> Clone for Expectation<T>

fn clone(&self) -> Expectation<T>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for Expectation<T>

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

Formats the value using the given formatter.

impl<T: Debug> Display for Expectation<T>

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

Formats the value using the given formatter.

impl<T: PartialEq> PartialEq for Expectation<T>

fn eq(&self, other: &Expectation<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: Copy> Copy for Expectation<T>

impl<T: Eq> Eq for Expectation<T>

impl<T> StructuralPartialEq for Expectation<T>