concat_idents.rs

// 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)])
}