4 releases
Uses new Rust 2024
new 0.1.3 | Mar 30, 2025 |
---|---|
0.1.2 | Mar 28, 2025 |
0.1.1 | Mar 26, 2025 |
0.1.0 | Mar 26, 2025 |
#1986 in Procedural macros
416 downloads per month
Used in 3 crates
9KB
macro_rules_attr
Use declarative macros as proc_macro attributes. (#[apply]
your macro_rules!
)
Usage
First, bring the apply
attribute macro into scope:
use macro_rules_attr::apply;
Then, define your macro using macro_rules!
:
# use macro_rules_attr::apply;
#
/// Your macro that you want to use as an attribute.
macro_rules! the_macro {
// Your macro implementation here.
# ($($tt:tt)*) => {}; // Matches and discards everything.
}
Finally, annotate your item with the apply
attribute macro:
# use macro_rules_attr::apply;
#
# /// Your macro that you want to use as an attribute.
# macro_rules! the_macro {
# // Your macro implementation here.
# ($($tt:tt)*) => {}; // Matches and discards everything.
# }
#
#[apply(the_macro)]
struct One {}
// Expands to:
the_macro! { struct One {} }
Additional tokens are appended after the annotated item:
# use macro_rules_attr::apply;
#
# /// Your macro that you want to use as an attribute.
# macro_rules! the_macro {
# // Your macro implementation here.
# ($($tt:tt)*) => {}; // Matches and discards everything.
# }
#
#[apply(the_macro, "additional tokens", anything, (you - like))]
struct Another {}
// Expands to:
the_macro! { struct Another {}, "additional tokens", anything, (you - like) }
Example
use macro_rules_attr::apply;
/// Simple macro that generates a `hello` function for given struct, which returns `Hello, {name}!`. If given a second argument, it will replace `{name}`.
macro_rules! make_hello {
( // Matches a struct definition (some details omitted for brevity)
# $(#[$struct_meta:meta])*
# $struct_vis:vis
struct $StructName:ident {
// ...
# $(
# $(#[$field_meta:meta])*
# $field_vis:vis
# $field_name:ident : $field_ty:ty
# ),* $(,)?
}$(, $replacement:expr)?
) => {
// Repeat the struct definition
# $(#[$struct_meta])*
# $struct_vis
struct $StructName {
// ...
# $(
# $(#[$field_meta])*
# $field_vis:vis $field_name: $field_ty,
# )*
}
// Implement the `hello` function
impl $StructName {
fn hello() -> String {
let name = stringify!($StructName);
$(let name = $replacement;)? // Shadow `name` if a replacement was provided
format!("Hello, {name}!")
}
}
};
}
#[apply(make_hello)] // No additional tokens
struct WithoutReplacement {}
assert_eq!(WithoutReplacement::hello(), "Hello, WithoutReplacement!");
#[apply(make_hello, "World")] // Additional tokens
struct WithReplacement {}
assert_eq!(WithReplacement::hello(), "Hello, World!");
Cargo Features
log
: Enable logging with thelog
crate. (Requireslog
as a dependency)
Comparison
This crate is heavily inspired by macro_rules_attribute, but differs in the following ways:
macro_rules_attr
is more lightweight and has no dependencies by default.- Less than 100 lines of code. (Excluding tests and documentation)
- You can enable logging with the
log
feature, which requireslog
as a dependency. paste
is required as a dev-dependency for the tests.
macro_rules_attr
only has one attribute:#[apply]
, whilemacro_rules_attribute
provides more.macro_rules_attr
allows you to append any tokens after the annotated item, whilemacro_rules_attribute
does not.
Dependencies
~23KB