1 // SPDX-License-Identifier: Apache-2.0 OR MIT
2
3 use proc_macro::{TokenStream, TokenTree};
4
5 pub(crate) fn pinned_drop(_args: TokenStream, input: TokenStream) -> TokenStream {
6 let mut toks = input.into_iter().collect::<Vec<_>>();
7 assert!(!toks.is_empty());
8 // Ensure that we have an `impl` item.
9 assert!(matches!(&toks[0], TokenTree::Ident(i) if i.to_string() == "impl"));
10 // Ensure that we are implementing `PinnedDrop`.
11 let mut nesting: usize = 0;
12 let mut pinned_drop_idx = None;
13 for (i, tt) in toks.iter().enumerate() {
14 match tt {
15 TokenTree::Punct(p) if p.as_char() == '<' => {
16 nesting += 1;
17 }
18 TokenTree::Punct(p) if p.as_char() == '>' => {
19 nesting = nesting.checked_sub(1).unwrap();
20 continue;
21 }
22 _ => {}
23 }
24 if i >= 1 && nesting == 0 {
25 // Found the end of the generics, this should be `PinnedDrop`.
26 assert!(
27 matches!(tt, TokenTree::Ident(i) if i.to_string() == "PinnedDrop"),
28 "expected 'PinnedDrop', found: '{:?}'",
29 tt
30 );
31 pinned_drop_idx = Some(i);
32 break;
33 }
34 }
35 let idx = pinned_drop_idx
36 .unwrap_or_else(|| panic!("Expected an `impl` block implementing `PinnedDrop`."));
37 // Fully qualify the `PinnedDrop`, as to avoid any tampering.
38 toks.splice(idx..idx, quote!(::kernel::init::));
39 // Take the `{}` body and call the declarative macro.
40 if let Some(TokenTree::Group(last)) = toks.pop() {
41 let last = last.stream();
42 quote!(::kernel::__pinned_drop! {
43 @impl_sig(#(#toks)*),
44 @impl_body(#last),
45 })
46 } else {
47 TokenStream::from_iter(toks)
48 }
49 }
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