Macro pseudo_element 

macro_rules! pseudo_element {
    ($(#[$meta:meta])* $vis:vis enum $name: ident { $first_variant: ident: $atoms: ident::$first:ident, $( $variant: ident: $variant_pat: pat$(,)?)* }) => { ... };
}

A macro for defining pseudo elements.

This makes it much easier to define a pseudo element. Parsing is also a little bit delicate, as the two Cursors must appear next to each other - no whitespace nor comments can be present betwixt the colon and ident.

Example

use css_parse::*;
use csskit_derives::*;
use derive_atom_set::*;
use bumpalo::Bump;

#[derive(Debug, Default, AtomSet, Copy, Clone, PartialEq)]
pub enum MyAtomSet {
  #[default]
  _None,
  Foo,
  Bar,
  Baz,
}
impl MyAtomSet {
  const ATOMS: MyAtomSet = MyAtomSet::_None;
}

pseudo_element!(
  /// Some docs on this type...
  #[derive(Debug, ToCursors, ToSpan)]
  pub enum MyPseudoElement {
    Foo: MyAtomSet::Foo,
    Bar: MyAtomSet::Bar,
    Baz: MyAtomSet::Baz,
  }
);

// Matches are case insensitive
assert_parse!(MyAtomSet::ATOMS, MyPseudoElement, "::FoO");

// The result will be one of the variants in the enum, matching the keyword.
assert_parse!(MyAtomSet::ATOMS, MyPseudoElement, "::bar");

// Words that do not match will fail to parse.
assert_parse_error!(MyAtomSet::ATOMS, MyPseudoElement, "::bing");