Expand description
A procedural macro helper for easily writing derives macros for enums.
§Examples
quick_derive!
macro make easy to write proc_macro_derive
like deriving trait to enum so long as all variants are implemented that trait.
use derive_utils::quick_derive;
use proc_macro::TokenStream;
#[proc_macro_derive(Iterator)]
pub fn derive_iterator(input: TokenStream) -> TokenStream {
quick_derive! {
input,
// trait path
std::iter::Iterator,
// trait definition
trait Iterator {
type Item;
fn next(&mut self) -> Option<Self::Item>;
fn size_hint(&self) -> (usize, Option<usize>);
}
}
}
#[proc_macro_derive(ExactSizeIterator)]
pub fn derive_exact_size_iterator(input: TokenStream) -> TokenStream {
quick_derive! {
input,
// trait path
std::iter::ExactSizeIterator,
// super trait's associated types
<Item>,
// trait definition
trait ExactSizeIterator: Iterator {
fn len(&self) -> usize;
}
}
}
§Generated code
When deriving for enum like the following:
#[derive(Iterator, ExactSizeIterator, Future)]
enum Enum<A, B> {
A(A),
B(B),
}
Code like this will be generated:
enum Enum<A, B> {
A(A),
B(B),
}
#[automatically_derived]
impl<A, B> std::iter::Iterator for Enum<A, B>
where
A: std::iter::Iterator,
B: std::iter::Iterator<Item = <A as std::iter::Iterator>::Item>,
{
type Item = <A as std::iter::Iterator>::Item;
fn next(&mut self) -> Option<Self::Item> {
match self {
Enum::A(x) => x.next(),
Enum::B(x) => x.next(),
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
match self {
Enum::A(x) => x.size_hint(),
Enum::B(x) => x.size_hint(),
}
}
}
#[automatically_derived]
impl<A, B> std::iter::ExactSizeIterator for Enum<A, B>
where
A: std::iter::ExactSizeIterator,
B: std::iter::ExactSizeIterator<Item = <A as Iterator>::Item>,
{
fn len(&self) -> usize {
match self {
Enum::A(x) => x.len(),
Enum::B(x) => x.len(),
}
}
}
§Related Projects
- auto_enums: A library for to allow multiple return types by automatically generated enum.
- io-enum: #[derive(Read, Write, Seek, BufRead)] for enums.
- iter-enum: #[derive(Iterator, DoubleEndedIterator, ExactSizeIterator, FusedIterator, Extend)] for enums.
Macros§
- A macro for making easy to write
proc_macro_derive
like deriving trait to enum so long as all variants are implemented that trait.
Structs§
- A structure to make trait implementation to enums more efficient.
- A builder for implementing a trait for enums.
Functions§
- A function for creating
proc_macro_derive
like deriving trait to enum so long as all variants are implemented that trait.