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