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// SPDX-License-Identifier: GPL-2.0
use proc_macro2::TokenStream;
use quote::quote;
use syn::{parse_quote, Data, DeriveInput, Field, Fields};
use crate::{diagnostics::ErrorGuaranteed, DiagCtxt};
pub(crate) fn derive(
input: DeriveInput,
dcx: &mut DiagCtxt,
) -> Result<TokenStream, ErrorGuaranteed> {
let fields = match input.data {
Data::Struct(data_struct) => data_struct.fields,
Data::Union(data_union) => Fields::Named(data_union.fields),
Data::Enum(data_enum) => {
return Err(dcx.error(data_enum.enum_token, "cannot derive `Zeroable` for an enum"));
}
};
let name = input.ident;
let mut generics = input.generics;
for param in generics.type_params_mut() {
param.bounds.insert(0, parse_quote!(::pin_init::Zeroable));
}
let (impl_gen, ty_gen, whr) = generics.split_for_impl();
let field_type = fields.iter().map(|field| &field.ty);
Ok(quote! {
// SAFETY: Every field type implements `Zeroable` and padding bytes may be zero.
#[automatically_derived]
unsafe impl #impl_gen ::pin_init::Zeroable for #name #ty_gen
#whr
{}
const _: () = {
fn assert_zeroable<T: ?::core::marker::Sized + ::pin_init::Zeroable>() {}
fn ensure_zeroable #impl_gen ()
#whr
{
#(
assert_zeroable::<#field_type>();
)*
}
};
})
}
pub(crate) fn maybe_derive(
input: DeriveInput,
dcx: &mut DiagCtxt,
) -> Result<TokenStream, ErrorGuaranteed> {
let fields = match input.data {
Data::Struct(data_struct) => data_struct.fields,
Data::Union(data_union) => Fields::Named(data_union.fields),
Data::Enum(data_enum) => {
return Err(dcx.error(data_enum.enum_token, "cannot derive `Zeroable` for an enum"));
}
};
let name = input.ident;
let mut generics = input.generics;
for param in generics.type_params_mut() {
param.bounds.insert(0, parse_quote!(::pin_init::Zeroable));
}
for Field { ty, .. } in fields {
generics
.make_where_clause()
.predicates
// the `for<'__dummy>` HRTB makes this not error without the `trivial_bounds`
// feature <https://github.com/rust-lang/rust/issues/48214#issuecomment-2557829956>.
.push(parse_quote!(#ty: for<'__dummy> ::pin_init::Zeroable));
}
let (impl_gen, ty_gen, whr) = generics.split_for_impl();
Ok(quote! {
// SAFETY: Every field type implements `Zeroable` and padding bytes may be zero.
#[automatically_derived]
unsafe impl #impl_gen ::pin_init::Zeroable for #name #ty_gen
#whr
{}
})
}
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