1 // SPDX-License-Identifier: GPL-2.0
2
3 use crate::helpers::{parse_generics, Generics};
4 use proc_macro::{TokenStream, TokenTree};
5
6 pub(crate) fn derive(input: TokenStream) -> TokenStream {
7 let (
8 Generics {
9 impl_generics,
10 decl_generics: _,
11 ty_generics,
12 },
13 mut rest,
14 ) = parse_generics(input);
15 // This should be the body of the struct `{...}`.
16 let last = rest.pop();
17 // Now we insert `Zeroable` as a bound for every generic parameter in `impl_generics`.
18 let mut new_impl_generics = Vec::with_capacity(impl_generics.len());
19 // Are we inside of a generic where we want to add `Zeroable`?
20 let mut in_generic = !impl_generics.is_empty();
21 // Have we already inserted `Zeroable`?
22 let mut inserted = false;
23 // Level of `<>` nestings.
24 let mut nested = 0;
25 for tt in impl_generics {
26 match &tt {
27 // If we find a `,`, then we have finished a generic/constant/lifetime parameter.
28 TokenTree::Punct(p) if nested == 0 && p.as_char() == ',' => {
29 if in_generic && !inserted {
30 new_impl_generics.extend(quote! { : ::kernel::init::Zeroable });
31 }
32 in_generic = true;
33 inserted = false;
34 new_impl_generics.push(tt);
35 }
36 // If we find `'`, then we are entering a lifetime.
37 TokenTree::Punct(p) if nested == 0 && p.as_char() == '\'' => {
38 in_generic = false;
39 new_impl_generics.push(tt);
40 }
41 TokenTree::Punct(p) if nested == 0 && p.as_char() == ':' => {
42 new_impl_generics.push(tt);
43 if in_generic {
44 new_impl_generics.extend(quote! { ::kernel::init::Zeroable + });
45 inserted = true;
46 }
47 }
48 TokenTree::Punct(p) if p.as_char() == '<' => {
49 nested += 1;
50 new_impl_generics.push(tt);
51 }
52 TokenTree::Punct(p) if p.as_char() == '>' => {
53 assert!(nested > 0);
54 nested -= 1;
55 new_impl_generics.push(tt);
56 }
57 _ => new_impl_generics.push(tt),
58 }
59 }
60 assert_eq!(nested, 0);
61 if in_generic && !inserted {
62 new_impl_generics.extend(quote! { : ::kernel::init::Zeroable });
63 }
64 quote! {
65 ::kernel::__derive_zeroable!(
66 parse_input:
67 @sig(#(#rest)*),
68 @impl_generics(#(#new_impl_generics)*),
69 @ty_generics(#(#ty_generics)*),
70 @body(#last),
71 );
72 }
73 }
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