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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
use derive_common::cg;
use proc_macro2::TokenStream;
use syn;
use synstructure::{BindStyle, Structure};
pub fn derive(mut input: syn::DeriveInput) -> TokenStream {
let mut where_clause = input.generics.where_clause.take();
let attrs = cg::parse_input_attrs::<ShmemInputAttrs>(&input);
if !attrs.no_bounds {
for param in input.generics.type_params() {
cg::add_predicate(&mut where_clause, parse_quote!(#param: ::to_shmem::ToShmem));
}
}
for variant in Structure::new(&input).variants() {
for binding in variant.bindings() {
let attrs = cg::parse_field_attrs::<ShmemFieldAttrs>(&binding.ast());
if attrs.field_bound {
let ty = &binding.ast().ty;
cg::add_predicate(&mut where_clause, parse_quote!(#ty: ::to_shmem::ToShmem))
}
}
}
input.generics.where_clause = where_clause;
// Do all of the `to_shmem()?` calls before the `ManuallyDrop::into_inner()`
// calls, so that we don't drop a value in the shared memory buffer if one
// of the `to_shmem`s fails.
let match_body = cg::fmap2_match(
&input,
BindStyle::Ref,
|binding| {
quote! {
::to_shmem::ToShmem::to_shmem(#binding, builder)?
}
},
|binding| {
Some(quote! {
::std::mem::ManuallyDrop::into_inner(#binding)
})
},
);
let name = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
quote! {
impl #impl_generics ::to_shmem::ToShmem for #name #ty_generics #where_clause {
#[allow(unused_variables, unreachable_code)]
fn to_shmem(
&self,
builder: &mut ::to_shmem::SharedMemoryBuilder,
) -> ::to_shmem::Result<Self> {
Ok(::std::mem::ManuallyDrop::new(
match *self {
#match_body
}
))
}
}
}
}
#[derive(Default, FromDeriveInput)]
#[darling(attributes(shmem), default)]
pub struct ShmemInputAttrs {
pub no_bounds: bool,
}
#[derive(Default, FromField)]
#[darling(attributes(shmem), default)]
pub struct ShmemFieldAttrs {
pub field_bound: bool,
}
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