projects/linux·blob master · refs

78 lines · 2.7 KiB

1// SPDX-License-Identifier: Apache-2.0 OR MIT
2
3use proc_macro2::TokenStream;
4use quote::quote;
5use syn::{parse_quote, Data, DeriveInput, Field, Fields};
6
7use crate::{diagnostics::ErrorGuaranteed, DiagCtxt};
8
9pub(crate) fn derive(
10 input: DeriveInput,
11 dcx: &mut DiagCtxt,
12) -> Result<TokenStream, ErrorGuaranteed> {
13 let fields = match input.data {
14 Data::Struct(data_struct) => data_struct.fields,
15 Data::Union(data_union) => Fields::Named(data_union.fields),
16 Data::Enum(data_enum) => {
17 return Err(dcx.error(data_enum.enum_token, "cannot derive `Zeroable` for an enum"));
18 }
19 };
20 let name = input.ident;
21 let mut generics = input.generics;
22 for param in generics.type_params_mut() {
23 param.bounds.insert(0, parse_quote!(::pin_init::Zeroable));
24 }
25 let (impl_gen, ty_gen, whr) = generics.split_for_impl();
26 let field_type = fields.iter().map(|field| &field.ty);
27 Ok(quote! {
28 // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero.
29 #[automatically_derived]
30 unsafe impl #impl_gen ::pin_init::Zeroable for #name #ty_gen
31 #whr
32 {}
33 const _: () = {
34 fn assert_zeroable<T: ?::core::marker::Sized + ::pin_init::Zeroable>() {}
35 fn ensure_zeroable #impl_gen ()
36 #whr
37 {
38 #(
39 assert_zeroable::<#field_type>();
40 )*
41 }
42 };
43 })
44}
45
46pub(crate) fn maybe_derive(
47 input: DeriveInput,
48 dcx: &mut DiagCtxt,
49) -> Result<TokenStream, ErrorGuaranteed> {
50 let fields = match input.data {
51 Data::Struct(data_struct) => data_struct.fields,
52 Data::Union(data_union) => Fields::Named(data_union.fields),
53 Data::Enum(data_enum) => {
54 return Err(dcx.error(data_enum.enum_token, "cannot derive `Zeroable` for an enum"));
55 }
56 };
57 let name = input.ident;
58 let mut generics = input.generics;
59 for param in generics.type_params_mut() {
60 param.bounds.insert(0, parse_quote!(::pin_init::Zeroable));
61 }
62 for Field { ty, .. } in fields {
63 generics
64 .make_where_clause()
65 .predicates
66 // the `for<'__dummy>` HRTB makes this not error without the `trivial_bounds`
67 // feature <https://github.com/rust-lang/rust/issues/48214#issuecomment-2557829956>.
68 .push(parse_quote!(#ty: for<'__dummy> ::pin_init::Zeroable));
69 }
70 let (impl_gen, ty_gen, whr) = generics.split_for_impl();
71 Ok(quote! {
72 // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero.
73 #[automatically_derived]
74 unsafe impl #impl_gen ::pin_init::Zeroable for #name #ty_gen
75 #whr
76 {}
77 })
78}