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[derive] Support deriving deprecated AsBytes #938

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Feb 23, 2024
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[derive] Support deriving deprecated AsBytes #938

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36 changes: 22 additions & 14 deletions zerocopy-derive/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -93,7 +93,7 @@ derive!(NoCell => derive_no_cell => derive_no_cell_inner);
derive!(TryFromBytes => derive_try_from_bytes => derive_try_from_bytes_inner);
derive!(FromZeros => derive_from_zeros => derive_from_zeros_inner);
derive!(FromBytes => derive_from_bytes => derive_from_bytes_inner);
derive!(IntoBytes => derive_as_bytes => derive_as_bytes_inner);
derive!(IntoBytes => derive_into_bytes => derive_into_bytes_inner);
derive!(Unaligned => derive_unaligned => derive_unaligned_inner);

/// Deprecated: prefer [`FromZeros`] instead.
Expand All @@ -104,6 +104,14 @@ pub fn derive_from_zeroes(ts: proc_macro::TokenStream) -> proc_macro::TokenStrea
derive_from_zeros(ts)
}

/// Deprecated: prefer [`IntoBytes`] instead.
#[deprecated(since = "0.8.0", note = "`AsBytes` was renamed to `IntoBytes`")]
#[doc(hidden)]
#[proc_macro_derive(AsBytes)]
pub fn derive_as_bytes(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
derive_into_bytes(ts)
}

fn derive_known_layout_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
let is_repr_c_struct = match &ast.data {
Data::Struct(..) => {
Expand Down Expand Up @@ -324,11 +332,11 @@ fn derive_from_bytes_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
IntoIterator::into_iter([from_zeros, from_bytes]).collect()
}

fn derive_as_bytes_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
fn derive_into_bytes_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
match &ast.data {
Data::Struct(strct) => derive_as_bytes_struct(ast, strct),
Data::Enum(enm) => derive_as_bytes_enum(ast, enm),
Data::Union(unn) => derive_as_bytes_union(ast, unn),
Data::Struct(strct) => derive_into_bytes_struct(ast, strct),
Data::Enum(enm) => derive_into_bytes_enum(ast, enm),
Data::Union(unn) => derive_into_bytes_union(ast, unn),
}
}

Expand Down Expand Up @@ -568,7 +576,7 @@ fn derive_from_zeros_enum(ast: &DeriveInput, enm: &DataEnum) -> proc_macro2::Tok

// We don't actually care what the repr is; we just care that it's one of
// the allowed ones.
try_or_print!(ENUM_FROM_ZEROS_AS_BYTES_CFG.validate_reprs(ast));
try_or_print!(ENUM_FROM_ZEROS_INTO_BYTES_CFG.validate_reprs(ast));

let has_explicit_zero_discriminant =
enm.variants.iter().filter_map(|v| v.discriminant.as_ref()).any(|(_, e)| {
Expand Down Expand Up @@ -687,8 +695,8 @@ fn derive_from_bytes_union(ast: &DeriveInput, unn: &DataUnion) -> proc_macro2::T
impl_block(ast, unn, Trait::FromBytes, FieldBounds::ALL_SELF, SelfBounds::None, None, None)
}

fn derive_as_bytes_struct(ast: &DeriveInput, strct: &DataStruct) -> proc_macro2::TokenStream {
let reprs = try_or_print!(STRUCT_UNION_AS_BYTES_CFG.validate_reprs(ast));
fn derive_into_bytes_struct(ast: &DeriveInput, strct: &DataStruct) -> proc_macro2::TokenStream {
let reprs = try_or_print!(STRUCT_UNION_INTO_BYTES_CFG.validate_reprs(ast));
let is_transparent = reprs.contains(&StructRepr::Transparent);
let is_packed = reprs.contains(&StructRepr::Packed);
let num_fields = strct.fields().len();
Expand Down Expand Up @@ -737,7 +745,7 @@ fn derive_as_bytes_struct(ast: &DeriveInput, strct: &DataStruct) -> proc_macro2:
impl_block(ast, strct, Trait::IntoBytes, field_bounds, SelfBounds::None, padding_check, None)
}

const STRUCT_UNION_AS_BYTES_CFG: Config<StructRepr> = Config {
const STRUCT_UNION_INTO_BYTES_CFG: Config<StructRepr> = Config {
// Since `disallowed_but_legal_combinations` is empty, this message will
// never actually be emitted.
allowed_combinations_message: r#"IntoBytes requires either a) repr "C" or "transparent" with all fields implementing IntoBytes or, b) repr "packed""#,
Expand All @@ -748,20 +756,20 @@ const STRUCT_UNION_AS_BYTES_CFG: Config<StructRepr> = Config {

// An enum is `IntoBytes` if it is field-less and has a defined repr.

fn derive_as_bytes_enum(ast: &DeriveInput, enm: &DataEnum) -> proc_macro2::TokenStream {
fn derive_into_bytes_enum(ast: &DeriveInput, enm: &DataEnum) -> proc_macro2::TokenStream {
if !enm.is_fieldless() {
return Error::new_spanned(ast, "only field-less enums can implement IntoBytes")
.to_compile_error();
}

// We don't care what the repr is; we only care that it is one of the
// allowed ones.
try_or_print!(ENUM_FROM_ZEROS_AS_BYTES_CFG.validate_reprs(ast));
try_or_print!(ENUM_FROM_ZEROS_INTO_BYTES_CFG.validate_reprs(ast));
impl_block(ast, enm, Trait::IntoBytes, FieldBounds::None, SelfBounds::None, None, None)
}

#[rustfmt::skip]
const ENUM_FROM_ZEROS_AS_BYTES_CFG: Config<EnumRepr> = {
const ENUM_FROM_ZEROS_INTO_BYTES_CFG: Config<EnumRepr> = {
use EnumRepr::*;
Config {
// Since `disallowed_but_legal_combinations` is empty, this message will
Expand Down Expand Up @@ -790,14 +798,14 @@ const ENUM_FROM_ZEROS_AS_BYTES_CFG: Config<EnumRepr> = {
// - `repr(C)`, `repr(transparent)`, or `repr(packed)`
// - no padding (size of union equals size of each field type)

fn derive_as_bytes_union(ast: &DeriveInput, unn: &DataUnion) -> proc_macro2::TokenStream {
fn derive_into_bytes_union(ast: &DeriveInput, unn: &DataUnion) -> proc_macro2::TokenStream {
// TODO(#10): Support type parameters.
if !ast.generics.params.is_empty() {
return Error::new(Span::call_site(), "unsupported on types with type parameters")
.to_compile_error();
}

try_or_print!(STRUCT_UNION_AS_BYTES_CFG.validate_reprs(ast));
try_or_print!(STRUCT_UNION_INTO_BYTES_CFG.validate_reprs(ast));

impl_block(
ast,
Expand Down