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[derive] Use macro to generate some scaffolding (#937)
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This allows us to define proc macros as functions that take an
already-parsed `&DeriveInput` rather than just a `TokenStream` which
must be parsed. This, in turn, allows us to pass an already-parsed
`&DeriveInput` when one proc macro invokes another (e.g., when the
derive for `FromBytes` invokes the derive for `FromZeros`) rather than
needing to clone the `TokenStream`.
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@joshlf
joshlf committed Feb 23, 2024
1 parent f4f80ce commit 18569a2
Showing 1 changed file with 67 additions and 79 deletions.
146 changes: 67 additions & 79 deletions zerocopy-derive/src/lib.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -72,10 +72,39 @@ macro_rules! try_or_print {
// (https://doc.rust-lang.org/nightly/proc_macro/struct.Span.html#method.error),
// which is currently unstable. Revisit this once it's stable.

#[proc_macro_derive(KnownLayout)]
pub fn derive_known_layout(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = syn::parse_macro_input!(ts as DeriveInput);
/// Defines a derive function named `$outer` which parses its input
/// `TokenStream` as a `DeriveInput` and then invokes the `$inner` function.
///
/// Note that the separate `$outer` parameter is required - proc macro functions
/// are currently required to live at the crate root, and so the caller must
/// specify the name in order to avoid name collisions.
macro_rules! derive {
($trait:ident => $outer:ident => $inner:ident) => {
#[proc_macro_derive($trait)]
pub fn $outer(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = syn::parse_macro_input!(ts as DeriveInput);
$inner(&ast).into()
}
};
}

derive!(KnownLayout => derive_known_layout => derive_known_layout_inner);
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!(Unaligned => derive_unaligned => derive_unaligned_inner);

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

fn derive_known_layout_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
let is_repr_c_struct = match &ast.data {
Data::Struct(..) => {
let reprs = try_or_print!(repr::reprs::<Repr>(&ast.attrs));
Expand Down Expand Up @@ -208,7 +237,7 @@ pub fn derive_known_layout(ts: proc_macro::TokenStream) -> proc_macro::TokenStre
// of an usized trailing field requires that the field is
// `KnownLayout`.
impl_block(
&ast,
ast,
strct,
Trait::KnownLayout,
require_trait_bound_on_field_types,
Expand All @@ -221,7 +250,7 @@ pub fn derive_known_layout(ts: proc_macro::TokenStream) -> proc_macro::TokenStre
// A bound on the trailing field is not required, since enums cannot
// currently be unsized.
impl_block(
&ast,
ast,
enm,
Trait::KnownLayout,
FieldBounds::None,
Expand All @@ -234,7 +263,7 @@ pub fn derive_known_layout(ts: proc_macro::TokenStream) -> proc_macro::TokenStre
// A bound on the trailing field is not required, since unions
// cannot currently be unsized.
impl_block(
&ast,
ast,
unn,
Trait::KnownLayout,
FieldBounds::None,
Expand All @@ -244,112 +273,71 @@ pub fn derive_known_layout(ts: proc_macro::TokenStream) -> proc_macro::TokenStre
)
}
}
.into()
}

#[proc_macro_derive(NoCell)]
pub fn derive_no_cell(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = syn::parse_macro_input!(ts as DeriveInput);
fn derive_no_cell_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
match &ast.data {
Data::Struct(strct) => impl_block(
&ast,
ast,
strct,
Trait::NoCell,
FieldBounds::ALL_SELF,
SelfBounds::None,
None,
None,
),
Data::Enum(enm) => impl_block(
&ast,
enm,
Trait::NoCell,
FieldBounds::ALL_SELF,
SelfBounds::None,
None,
None,
),
Data::Union(unn) => impl_block(
&ast,
unn,
Trait::NoCell,
FieldBounds::ALL_SELF,
SelfBounds::None,
None,
None,
),
Data::Enum(enm) => {
impl_block(ast, enm, Trait::NoCell, FieldBounds::ALL_SELF, SelfBounds::None, None, None)
}
Data::Union(unn) => {
impl_block(ast, unn, Trait::NoCell, FieldBounds::ALL_SELF, SelfBounds::None, None, None)
}
}
.into()
}

#[proc_macro_derive(TryFromBytes)]
pub fn derive_try_from_bytes(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = syn::parse_macro_input!(ts as DeriveInput);
fn derive_try_from_bytes_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
match &ast.data {
Data::Struct(strct) => derive_try_from_bytes_struct(&ast, strct),
Data::Enum(enm) => derive_try_from_bytes_enum(&ast, enm),
Data::Union(unn) => derive_try_from_bytes_union(&ast, unn),
Data::Struct(strct) => derive_try_from_bytes_struct(ast, strct),
Data::Enum(enm) => derive_try_from_bytes_enum(ast, enm),
Data::Union(unn) => derive_try_from_bytes_union(ast, unn),
}
.into()
}

#[proc_macro_derive(FromZeros)]
pub fn derive_from_zeros(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
let try_from_bytes = derive_try_from_bytes(ts.clone());

let ast = syn::parse_macro_input!(ts as DeriveInput);
fn derive_from_zeros_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
let try_from_bytes = derive_try_from_bytes_inner(ast);
let from_zeros = match &ast.data {
Data::Struct(strct) => derive_from_zeros_struct(&ast, strct),
Data::Enum(enm) => derive_from_zeros_enum(&ast, enm),
Data::Union(unn) => derive_from_zeros_union(&ast, unn),
}
.into();
Data::Struct(strct) => derive_from_zeros_struct(ast, strct),
Data::Enum(enm) => derive_from_zeros_enum(ast, enm),
Data::Union(unn) => derive_from_zeros_union(ast, unn),
};
IntoIterator::into_iter([try_from_bytes, from_zeros]).collect()
}

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

#[proc_macro_derive(FromBytes)]
pub fn derive_from_bytes(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
let from_zeros = derive_from_zeros(ts.clone());

let ast = syn::parse_macro_input!(ts as DeriveInput);
fn derive_from_bytes_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
let from_zeros = derive_from_zeros_inner(ast);
let from_bytes = match &ast.data {
Data::Struct(strct) => derive_from_bytes_struct(&ast, strct),
Data::Enum(enm) => derive_from_bytes_enum(&ast, enm),
Data::Union(unn) => derive_from_bytes_union(&ast, unn),
}
.into();
Data::Struct(strct) => derive_from_bytes_struct(ast, strct),
Data::Enum(enm) => derive_from_bytes_enum(ast, enm),
Data::Union(unn) => derive_from_bytes_union(ast, unn),
};

IntoIterator::into_iter([from_zeros, from_bytes]).collect()
}

#[proc_macro_derive(IntoBytes)]
pub fn derive_as_bytes(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = syn::parse_macro_input!(ts as DeriveInput);
fn derive_as_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_as_bytes_struct(ast, strct),
Data::Enum(enm) => derive_as_bytes_enum(ast, enm),
Data::Union(unn) => derive_as_bytes_union(ast, unn),
}
.into()
}

#[proc_macro_derive(Unaligned)]
pub fn derive_unaligned(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = syn::parse_macro_input!(ts as DeriveInput);
fn derive_unaligned_inner(ast: &DeriveInput) -> proc_macro2::TokenStream {
match &ast.data {
Data::Struct(strct) => derive_unaligned_struct(&ast, strct),
Data::Enum(enm) => derive_unaligned_enum(&ast, enm),
Data::Union(unn) => derive_unaligned_union(&ast, unn),
Data::Struct(strct) => derive_unaligned_struct(ast, strct),
Data::Enum(enm) => derive_unaligned_enum(ast, enm),
Data::Union(unn) => derive_unaligned_union(ast, unn),
}
.into()
}

// A struct is `TryFromBytes` if:
Expand Down

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