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60f18c225f
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: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Finn Behrens <me@kloenk.dev>
Reviewed-by: Gary Guo <gary@garyguo.net>
[Reworded, adapted for upstream and applied latest changes]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
23 lines
712 B
Rust
23 lines
712 B
Rust
// SPDX-License-Identifier: GPL-2.0
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use proc_macro::{token_stream, Ident, TokenStream, TokenTree};
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use crate::helpers::expect_punct;
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fn expect_ident(it: &mut token_stream::IntoIter) -> Ident {
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if let Some(TokenTree::Ident(ident)) = it.next() {
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ident
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} else {
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panic!("Expected Ident")
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}
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}
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pub(crate) fn concat_idents(ts: TokenStream) -> TokenStream {
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let mut it = ts.into_iter();
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let a = expect_ident(&mut it);
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assert_eq!(expect_punct(&mut it), ',');
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let b = expect_ident(&mut it);
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assert!(it.next().is_none(), "only two idents can be concatenated");
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let res = Ident::new(&format!("{a}{b}"), b.span());
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TokenStream::from_iter([TokenTree::Ident(res)])
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}
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