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// SPDX-License-Identifier: Apache-2.0 OR MIT
use proc_macro::{TokenStream, TokenTree};
pub(crate) fn pinned_drop(_args: TokenStream, input: TokenStream) -> TokenStream {
let mut toks = input.into_iter().collect::<Vec<_>>();
assert!(!toks.is_empty());
// Ensure that we have an `impl` item.
assert!(matches!(&toks[0], TokenTree::Ident(i) if i.to_string() == "impl"));
// Ensure that we are implementing `PinnedDrop`.
let mut nesting: usize = 0;
let mut pinned_drop_idx = None;
for (i, tt) in toks.iter().enumerate() {
match tt {
TokenTree::Punct(p) if p.as_char() == '<' => {
nesting += 1;
}
TokenTree::Punct(p) if p.as_char() == '>' => {
nesting = nesting.checked_sub(1).unwrap();
continue;
}
_ => {}
}
if i >= 1 && nesting == 0 {
// Found the end of the generics, this should be `PinnedDrop`.
assert!(
matches!(tt, TokenTree::Ident(i) if i.to_string() == "PinnedDrop"),
"expected 'PinnedDrop', found: '{:?}'",
tt
);
pinned_drop_idx = Some(i);
break;
}
}
let idx = pinned_drop_idx
.unwrap_or_else(|| panic!("Expected an `impl` block implementing `PinnedDrop`."));
// Fully qualify the `PinnedDrop`, as to avoid any tampering.
toks.splice(idx..idx, quote!(::kernel::init::));
// Take the `{}` body and call the declarative macro.
if let Some(TokenTree::Group(last)) = toks.pop() {
let last = last.stream();
quote!(::kernel::__pinned_drop! {
@impl_sig(#(#toks)*),
@impl_body(#last),
})
} else {
TokenStream::from_iter(toks)
}
}
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