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// SPDX-License-Identifier: GPL-2.0
use crate::helpers::{parse_generics, Generics};
use proc_macro::{TokenStream, TokenTree};
pub(crate) fn derive(input: TokenStream) -> TokenStream {
let (
Generics {
impl_generics,
ty_generics,
},
mut rest,
) = parse_generics(input);
// This should be the body of the struct `{...}`.
let last = rest.pop();
// Now we insert `Zeroable` as a bound for every generic parameter in `impl_generics`.
let mut new_impl_generics = Vec::with_capacity(impl_generics.len());
// Are we inside of a generic where we want to add `Zeroable`?
let mut in_generic = !impl_generics.is_empty();
// Have we already inserted `Zeroable`?
let mut inserted = false;
// Level of `<>` nestings.
let mut nested = 0;
for tt in impl_generics {
match &tt {
// If we find a `,`, then we have finished a generic/constant/lifetime parameter.
TokenTree::Punct(p) if nested == 0 && p.as_char() == ',' => {
if in_generic && !inserted {
new_impl_generics.extend(quote! { : ::kernel::init::Zeroable });
}
in_generic = true;
inserted = false;
new_impl_generics.push(tt);
}
// If we find `'`, then we are entering a lifetime.
TokenTree::Punct(p) if nested == 0 && p.as_char() == '\'' => {
in_generic = false;
new_impl_generics.push(tt);
}
TokenTree::Punct(p) if nested == 0 && p.as_char() == ':' => {
new_impl_generics.push(tt);
if in_generic {
new_impl_generics.extend(quote! { ::kernel::init::Zeroable + });
inserted = true;
}
}
TokenTree::Punct(p) if p.as_char() == '<' => {
nested += 1;
new_impl_generics.push(tt);
}
TokenTree::Punct(p) if p.as_char() == '>' => {
assert!(nested > 0);
nested -= 1;
new_impl_generics.push(tt);
}
_ => new_impl_generics.push(tt),
}
}
assert_eq!(nested, 0);
if in_generic && !inserted {
new_impl_generics.extend(quote! { : ::kernel::init::Zeroable });
}
quote! {
::kernel::__derive_zeroable!(
parse_input:
@sig(#(#rest)*),
@impl_generics(#(#new_impl_generics)*),
@ty_generics(#(#ty_generics)*),
@body(#last),
);
}
}
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