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// Copyright (c) 2016 macro-attr contributors.
// Copyright (c) 2020 Warlock <internalmike@gmail.com>.
// Copyright (c) 2020 Clint Armstrong <clint@clintarmstrong.net>.
//
// Licensed under the MIT license (see LICENSE or <http://opensource.org
// /licenses/MIT>) or the Apache License, Version 2.0 (see LICENSE of
// <http://www.apache.org/licenses/LICENSE-2.0>), at your option. All
// files in the project carrying such notice may not be copied, modified,
// or distributed except according to those terms.
#![deny(warnings)]
#![doc(test(attr(deny(warnings))))]
#![doc(test(attr(allow(dead_code))))]
#![doc(test(attr(allow(unused_variables))))]
#![doc(test(attr(allow(unused_macros))))]
#![doc(test(attr(allow(unknown_lints, unused_macro_rules))))]
//! This crate provides the `macro_attr!` macro that enables the use of custom,
//! macro-based attributes and derivations.
//!
//! The `macro_attr!` macro should be used to wrap an entire *single* item
//! (`enum`, `struct`, *etc.*) declaration, including its attributes (both `derive` and others).
//! All attributes and derivations which whose names end with `!` will be assumed
//! to be implemented by macros, and treated accordingly.
//!
//! ```rust
//! use macro_attr_2018::macro_attr;
//!
//! // Define some traits to be derived.
//!
//! trait TypeName {
//! fn type_name() -> &'static str;
//! }
//!
//! trait ReprType {
//! type Repr;
//! }
//!
//! // Define macros which derive implementations of these macros.
//!
//! macro_rules! TypeName {
//! // We can support any kind of item we want.
//! (() $vis:vis enum $name:ident $($tail:tt)+) => { TypeName! { @impl $name } };
//! (() $vis:vis struct $name:ident $($tail:tt)+) => { TypeName! { @impl $name } };
//!
//! // Inner rule to cut down on repetition.
//! (@impl $name:ident) => {
//! impl TypeName for $name {
//! fn type_name() -> &'static str { stringify!($name) }
//! }
//! };
//! }
//!
//! macro_rules! ReprType {
//! // Note that we use a "derivation argument" here for the `$repr` type.
//! (($repr:ty) $vis:vis enum $name:ident $($tail:tt)+) => {
//! impl ReprType for $name {
//! type Repr = $repr;
//! }
//! };
//! }
//!
//! // Derive.
//!
//! macro_attr! {
//! #[derive(TypeName!, ReprType!(u16))]
//! #[repr(u16)]
//! enum SomeEnum { A, B, C, D }
//! }
//!
//! # fn main() {
//! assert_eq!(SomeEnum::type_name(), "SomeEnum");
//! assert_eq!(SomeEnum::A as <SomeEnum as ReprType>::Repr, 0u16);
//! # }
//! ```
#![no_std]
#[doc=include_str!("../README.md")]
type _DocTestReadme = ();
/// When given an item definition, including its attributes, this macro parses said attributes
/// and dispatches any derivations suffixed with `!` to user-defined macros.
/// This allows multiple macros to process the same item.
///
/// Given the following input:
///
/// ```ignore
/// #[derive(Copy, Name!(args...), Clone, Another!, Debug)]
/// struct Foo;
/// ```
///
/// `macro_attr!` will expand to the equivalent of:
///
/// ```ignore
/// #[derive(Copy, Clone, Debug)]
/// struct Foo;
///
/// Name!((args...) struct Foo;);
/// Another!(() struct Foo;);
/// ```
///
/// Note that macro derives may be mixed with regular derives,
/// or put in their own `#[derive(...)]` attribute.
/// Also note that macro derive invocations are *not* passed the other attributes on the item;
/// input will consist of the arguments provided to the derivation (*i.e.* `(args...)`
/// in this example), the item's visibility (if any), and the item definition itself.
///
/// A macro derivation invoked *without* arguments will be treated as though
/// it was invoked with empty parentheses. *i.e.* `#[derive(Name!)]` is equivalent to `#[derive(Name!())]`.
///
/// A derivation macro may expand to any number of new items derived from the provided input.
#[macro_export]
macro_rules! macro_attr {
(
$(#[$($attrs:tt)+])*
$(pub $(($($vis:tt)+))?)? enum $($it:tt)+
) => {
$crate::macro_attr_impl! {
@split_attrs [$(pub $(($($vis)+))?)? enum $($it)+]
[] []
[$([$($attrs)+])*]
}
};
(
$(#[$($attrs:tt)+])*
$(pub $(($($vis:tt)+))?)? struct $($it:tt)+
) => {
$crate::macro_attr_impl! {
@split_attrs [$(pub $(($($vis)+))?)? struct $($it)+]
[] []
[$([$($attrs)+])*]
}
};
(
$(#[$($attrs:tt)+])*
$(pub $(($($vis:tt)+))?)? trait $($it:tt)+
) => {
$crate::macro_attr_impl! {
@split_attrs [$(pub ($($vis)+))? trait $($it)+]
[] []
[$([$($attrs)+])*]
}
};
(
$(#[$($attrs:tt)+])*
$vis:vis $keyword:ident $($it:tt)+
) => {
$crate::macro_attr_impl! {
@split_attrs [$vis $keyword $($it)+]
[] []
[$([$($attrs)+])*]
}
};
}
#[doc(hidden)]
#[macro_export]
macro_rules! macro_attr_impl {
(
@split_attrs [$($it:tt)+]
[$($derive_attrs:tt)*] [$([$other_attrs:meta])*]
[[derive($($derive_attr:tt)+)] $([$($attrs:tt)+])*]
) => {
$crate::macro_attr_impl! {
@split_attrs [$($it)+]
[$($derive_attrs)* [$($derive_attr)+]]
[$([$other_attrs])*]
[$([$($attrs)+])*]
}
};
(
@split_attrs [$($it:tt)+]
[$($derive_attrs:tt)*] [$([$other_attrs:meta])*]
[[$attr:meta] $([$($attrs:tt)+])*]
) => {
$crate::macro_attr_impl! {
@split_attrs [$($it)+]
[$($derive_attrs)*]
[$([$other_attrs])* [$attr]]
[$([$($attrs)+])*]
}
};
(
@split_attrs [$($it:tt)+]
[$($derive_attrs:tt)*] [$([$other_attrs:meta])*]
[]
) => {
$crate::macro_attr_impl! {
@split_derive_attrs [$($it)+] [$([$other_attrs])*]
[] []
[$($derive_attrs)*]
}
};
(
@split_derive_attrs [$($it:tt)+] [$([$other_attrs:meta])*]
[$($macro_derives:tt)*] [$($std_derives:tt)*]
[
[$macro_derive:ident ! $(($($macro_derive_args:tt)*))? $(, $($other_inner_derives:tt)*)?]
$([$($other_derives:tt)*])*
]
) => {
$crate::macro_attr_impl! {
@split_derive_attrs [$($it)+] [$([$other_attrs])*]
[
$($macro_derives)*
[$macro_derive ( $($($macro_derive_args)*)? )]
]
[
$($std_derives)*
]
[
$([$($other_inner_derives)*])?
$([$($other_derives)*])*
]
}
};
(
@split_derive_attrs [$($it:tt)+] [$([$other_attrs:meta])*]
[$($macro_derives:tt)*] [$($std_derives:tt)*]
[
[$std_derive:ident $(($($std_derive_args:tt)*))? $(, $($other_inner_derives:tt)*)?]
$([$($other_derives:tt)*])*
]
) => {
$crate::macro_attr_impl! {
@split_derive_attrs [$($it)+] [$([$other_attrs])*]
[
$($macro_derives)*
]
[
$($std_derives)*
#[derive($std_derive $(($($std_derive_args)*))?)]
]
[
$([$($other_inner_derives)*])?
$([$($other_derives)*])*
]
}
};
(
@split_derive_attrs [$($it:tt)+] [$([$other_attrs:meta])*]
[$($macro_derives:tt)*] [$($std_derives:tt)*]
[
[]
$([$($other_derives:tt)*])*
]
) => {
$crate::macro_attr_impl! {
@split_derive_attrs [$($it)+] [$([$other_attrs])*]
[
$($macro_derives)*
]
[
$($std_derives)*
]
[
$([$($other_derives)*])*
]
}
};
(
@split_derive_attrs [$($it:tt)+] [$([$other_attrs:meta])*]
[$([$macro_derive:ident ( $($macro_derive_args:tt)* )])*]
[$($std_derives:tt)*]
[]
) => {
$crate::macro_attr_impl! {
@as_item
$($std_derives)*
$(#[$other_attrs])*
$($it)+
}
$crate::macro_attr_impl! {
@expand [$($it)+]
[$([$macro_derive ( $($macro_derive_args)* )])*]
}
};
(
@expand [$($it:tt)+]
[
[$macro_derive:ident ( $($macro_derive_args:tt)* )]
$([$other_macro_derives:ident ( $($other_macro_derives_args:tt)* )])*
]
) => {
$macro_derive! {
( $($macro_derive_args)* )
$($it)+
}
$crate::macro_attr_impl! {
@expand [$($it)+]
[$([$other_macro_derives ( $($other_macro_derives_args)* )])*]
}
};
(
@expand [$($it:tt)+]
[]
) => {
};
(@as_item $($i:item)*) => {$($i)*};
}