Commit 60f18c22 authored by Björn Roy Baron's avatar Björn Roy Baron Committed by Miguel Ojeda
Browse files

rust: macros: add `concat_idents!` proc macro 



This macro provides similar functionality to the unstable feature
`concat_idents` without having to rely on it.

For instance:

    let x_1 = 42;
    let x_2 = concat_idents!(x, _1);
    assert!(x_1 == x_2);

It has different behavior with respect to macro hygiene. Unlike
the unstable `concat_idents!` macro, it allows, for example,
referring to local variables by taking the span of the second
macro as span for the output identifier.

Signed-off-by: default avatarBjörn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: default avatarFinn Behrens <me@kloenk.dev>
Reviewed-by: default avatarGary Guo <gary@garyguo.net>
[Reworded, adapted for upstream and applied latest changes]
Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent c3630df6

rust/macros/concat_idents.rs

0 → 100644
+23 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



use proc_macro::{token_stream, Ident, TokenStream, TokenTree};



use crate::helpers::expect_punct;



fn expect_ident(it: &mut token_stream::IntoIter) -> Ident {

    if let Some(TokenTree::Ident(ident)) = it.next() {

        ident

    } else {

        panic!("Expected Ident")

    }

}



pub(crate) fn concat_idents(ts: TokenStream) -> TokenStream {

    let mut it = ts.into_iter();

    let a = expect_ident(&mut it);

    assert_eq!(expect_punct(&mut it), ',');

    let b = expect_ident(&mut it);

    assert!(it.next().is_none(), "only two idents can be concatenated");

    let res = Ident::new(&format!("{a}{b}"), b.span());

    TokenStream::from_iter([TokenTree::Ident(res)])

}

rust/macros/lib.rs

+44 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 


//! Crate for all kernel procedural macros.



mod concat_idents;

mod helpers;

mod module;
@@ -70,3 +71,46 @@ use proc_macro::TokenStream; 
pub fn module(ts: TokenStream) -> TokenStream {

    module::module(ts)

}



/// Concatenate two identifiers.

///

/// This is useful in macros that need to declare or reference items with names

/// starting with a fixed prefix and ending in a user specified name. The resulting

/// identifier has the span of the second argument.

///

/// # Examples

///

/// ```ignore

/// use kernel::macro::concat_idents;

///

/// macro_rules! pub_no_prefix {

///     ($prefix:ident, $($newname:ident),+) => {

///         $(pub(crate) const $newname: u32 = kernel::macros::concat_idents!($prefix, $newname);)+

///     };

/// }

///

/// pub_no_prefix!(

///     binder_driver_return_protocol_,

///     BR_OK,

///     BR_ERROR,

///     BR_TRANSACTION,

///     BR_REPLY,

///     BR_DEAD_REPLY,

///     BR_TRANSACTION_COMPLETE,

///     BR_INCREFS,

///     BR_ACQUIRE,

///     BR_RELEASE,

///     BR_DECREFS,

///     BR_NOOP,

///     BR_SPAWN_LOOPER,

///     BR_DEAD_BINDER,

///     BR_CLEAR_DEATH_NOTIFICATION_DONE,

///     BR_FAILED_REPLY

/// );

///

/// assert_eq!(BR_OK, binder_driver_return_protocol_BR_OK);

/// ```

#[proc_macro]

pub fn concat_idents(ts: TokenStream) -> TokenStream {

    concat_idents::concat_idents(ts)

}