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#![deny(
missing_docs,
unsafe_op_in_unsafe_fn,
clippy::as_conversions,
clippy::missing_safety_doc,
clippy::undocumented_unsafe_blocks,
rustdoc::broken_intra_doc_links,
rustdoc::missing_crate_level_docs
)]
use ::macroix::{
case::pascal_to_snake,
repr::{BaseKind, Int, PrimitiveType, Repr},
};
use ::proc_macro2::{Span, TokenStream};
use ::quote::quote;
use ::syn::{
Data,
DataEnum,
DeriveInput,
Error,
Fields,
Generics,
Ident,
Variant,
};
pub struct RawIdents {
pub r#enum: Ident,
pub discriminant: Ident,
pub fields: Ident,
pub variants: Ident,
variant_prefix: String,
pub raw_enum_fn: Ident,
pub discriminant_fn: Ident,
pub variant_fn: Ident,
}
impl RawIdents {
fn for_enum(ident: &Ident) -> Self {
let snake_case = pascal_to_snake(&ident.to_string());
Self {
r#enum: Ident::new(&format!("Raw{ident}Enum"), ident.span()),
discriminant: Ident::new(
&format!("Raw{ident}Discriminant"),
ident.span(),
),
fields: Ident::new(&format!("Raw{ident}Fields"), ident.span()),
variants: Ident::new(&format!("Raw{ident}Variants"), ident.span()),
variant_prefix: format!("Raw{ident}Variant"),
raw_enum_fn: Ident::new(&format!("raw_{snake_case}"), ident.span()),
discriminant_fn: Ident::new(
&format!("raw_{snake_case}_discriminant"),
ident.span(),
),
variant_fn: Ident::new(
&format!("raw_{snake_case}_variant"),
ident.span(),
),
}
}
pub fn variant(&self, variant: &Ident) -> Ident {
Ident::new(
&format!("{}{}", self.variant_prefix, variant),
variant.span(),
)
}
}
pub struct RawEnum {
pub idents: RawIdents,
pub tokens: TokenStream,
}
impl RawEnum {
pub fn for_derive(input: &DeriveInput) -> Result<RawEnum, Error> {
let idents = RawIdents::for_enum(&input.ident);
let mut repr = None;
for attr in input.attrs.iter() {
if attr.path.is_ident("repr") {
Repr::merge_attr(&mut repr, attr.tokens.clone())?;
}
}
let data = match input.data {
Data::Struct(ref data) => {
return Err(Error::new_spanned(
data.struct_token,
format!("`{}` is not an enum", input.ident),
))
}
Data::Enum(ref data) => data,
Data::Union(ref data) => {
return Err(Error::new_spanned(
data.union_token,
format!("`{}` is not an enum", input.ident),
))
}
};
let repr = repr.ok_or_else(|| {
Error::new(
Span::call_site(),
format!(
"`{}` requires an explicit `repr` attribute",
input.ident
),
)
})?;
let base = repr.base.ok_or_else(|| {
Error::new(
Span::call_site(),
format!("`{}` requires a base `repr`", input.ident),
)
})?;
let tokens = match base.kind {
BaseKind::C => {
derive_c(data, &input.generics, repr.primitive_type, &idents)?
}
BaseKind::Primitive(int) => {
derive_primitive(data, &input.generics, int, &idents)?
}
BaseKind::Transparent => {
return Err(Error::new_spanned(
base.kind_token,
format!(
"`{}` must have a base `repr` of `C` or a primitive",
input.ident,
),
))
}
};
let raw_enum_ident = &idents.r#enum;
let discriminant_ident = &idents.discriminant;
let raw_enum_fn_ident = &idents.raw_enum_fn;
let discriminant_fn_ident = &idents.discriminant_fn;
let input_ident = &input.ident;
let (impl_generics, ty_generics, where_clause) =
input.generics.split_for_impl();
let tokens = quote! {
#tokens
fn #raw_enum_fn_ident #impl_generics (
this: *mut #input_ident #ty_generics,
) -> *mut #raw_enum_ident #ty_generics
#where_clause
{
#[repr(C)]
union Reinterpret<T, U> {
from: ::core::mem::ManuallyDrop<T>,
to: ::core::mem::ManuallyDrop<U>,
}
let reinterpret = Reinterpret {
from: ::core::mem::ManuallyDrop::new(this),
};
::core::mem::ManuallyDrop::into_inner(unsafe { reinterpret.to })
}
fn #discriminant_fn_ident #impl_generics (
this: *mut #raw_enum_ident #ty_generics,
) -> *mut #discriminant_ident
#where_clause
{
this.cast::<#discriminant_ident>()
}
};
Ok(RawEnum { idents, tokens })
}
}
fn generate_discriminant(
data: &DataEnum,
base: BaseKind,
idents: &RawIdents,
) -> TokenStream {
let discriminant = &idents.discriminant;
let variants = data.variants.iter().map(|v| {
let ident = &v.ident;
if let Some((eq, discriminant)) = &v.discriminant {
quote! { #ident #eq #discriminant }
} else {
quote! { #ident }
}
});
quote! {
#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
#[repr(#base)]
#[allow(dead_code)]
enum #discriminant {
#(#variants),*
}
}
}
fn generate_variant_struct(
variant: &Variant,
generics: &Generics,
idents: &RawIdents,
with_tag: bool,
) -> TokenStream {
let discriminant_ident = &idents.discriminant;
let variant_struct_ident = idents.variant(&variant.ident);
let type_params = generics.type_params().map(|p| &p.ident);
let phantom_ty = quote! {
::core::marker::PhantomData<(#(#type_params,)*)>
};
let (impl_generics, _, where_clause) = generics.split_for_impl();
let tag_ty = if with_tag {
quote! { #discriminant_ident }
} else {
quote! { () }
};
match &variant.fields {
Fields::Named(fields) => {
let fields = fields.named.iter().map(|f| {
let ident = &f.ident;
let ty = &f.ty;
quote! {
pub #ident: #ty
}
});
quote! {
#[repr(C)]
#[allow(non_snake_case)]
struct #variant_struct_ident #impl_generics #where_clause {
__tag: #tag_ty,
#(#fields,)*
_phantom: #phantom_ty,
}
}
}
Fields::Unnamed(fields) => {
let fields = fields.unnamed.iter().map(|f| {
let ty = &f.ty;
quote! {
pub #ty
}
});
quote! {
#[repr(C)]
#[allow(non_snake_case)]
struct #variant_struct_ident #impl_generics (
#tag_ty,
#(#fields,)*
#phantom_ty,
) #where_clause;
}
}
Fields::Unit => {
quote! {
#[repr(C)]
#[allow(non_snake_case)]
struct #variant_struct_ident #impl_generics (
#tag_ty,
#phantom_ty,
) #where_clause;
}
}
}
}
fn generate_variants(
data: &DataEnum,
generics: &Generics,
idents: &RawIdents,
) -> TokenStream {
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let variants = data.variants.iter().map(|v| {
let ident = &v.ident;
let variant_struct_ident = idents.variant(ident);
quote! { #ident (*mut #variant_struct_ident #ty_generics) }
});
let variants_ident = &idents.variants;
quote! {
#[allow(dead_code)]
enum #variants_ident #impl_generics #where_clause {
#(#variants,)*
}
}
}
fn derive_c(
data: &DataEnum,
generics: &Generics,
primitive: Option<PrimitiveType>,
idents: &RawIdents,
) -> Result<TokenStream, Error> {
let discriminant = generate_discriminant(
data,
primitive
.map(|p| BaseKind::Primitive(p.int))
.unwrap_or(BaseKind::C),
idents,
);
let variant_structs = data.variants.iter().map(|variant| {
generate_variant_struct(variant, generics, idents, false)
});
let variants = generate_variants(data, generics, idents);
let raw_ident = &idents.r#enum;
let discriminant_ident = &idents.discriminant;
let fields_ident = &idents.fields;
let variants_ident = &idents.variants;
let discriminant_fn_ident = &idents.discriminant_fn;
let variant_fn_ident = &idents.variant_fn;
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let variant_idents = data.variants.iter().map(|v| &v.ident);
let variant_struct_idents =
data.variants.iter().map(|v| idents.variant(&v.ident));
let variants_arms = data.variants.iter().map(|v| {
let ident = &v.ident;
let variant_struct_ident = idents.variant(&v.ident);
quote! {
#discriminant_ident::#ident => {
let field = unsafe {
::core::ptr::addr_of_mut!((*this).fields.#ident)
};
#variants_ident::#ident(
field.cast::<#variant_struct_ident #ty_generics>()
)
}
}
});
Ok(quote! {
#discriminant
#(#variant_structs)*
#[repr(C)]
#[allow(non_snake_case)]
union #fields_ident #impl_generics #where_clause {
#(
pub #variant_idents: ::core::mem::ManuallyDrop<
#variant_struct_idents #ty_generics,
>,
)*
}
#[repr(C)]
struct #raw_ident #impl_generics #where_clause {
pub __tag: #discriminant_ident,
pub fields: #fields_ident #ty_generics,
}
#variants
fn #variant_fn_ident #impl_generics (
this: *mut #raw_ident #ty_generics,
) -> #variants_ident #ty_generics
#where_clause
{
match unsafe { *#discriminant_fn_ident(this) } {
#(#variants_arms,)*
}
}
})
}
fn derive_primitive(
data: &DataEnum,
generics: &Generics,
int: Int,
idents: &RawIdents,
) -> Result<TokenStream, Error> {
let discriminant =
generate_discriminant(data, BaseKind::Primitive(int), idents);
let variant_structs = data.variants.iter().map(|variant| {
generate_variant_struct(variant, generics, idents, true)
});
let variants = generate_variants(data, generics, idents);
let raw_ident = &idents.r#enum;
let discriminant_ident = &idents.discriminant;
let variants_ident = &idents.variants;
let discriminant_fn_ident = &idents.discriminant_fn;
let variant_fn_ident = &idents.variant_fn;
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let variant_idents = data.variants.iter().map(|v| &v.ident);
let variant_struct_idents =
data.variants.iter().map(|v| idents.variant(&v.ident));
let variants_arms = data.variants.iter().map(|v| {
let ident = &v.ident;
let variant_struct_ident = idents.variant(&v.ident);
quote! {
#discriminant_ident::#ident => {
let field = unsafe {
::core::ptr::addr_of_mut!((*this).#ident)
};
#variants_ident::#ident(
field.cast::<#variant_struct_ident #ty_generics>()
)
}
}
});
Ok(quote! {
#discriminant
#(#variant_structs)*
#[repr(C)]
#[allow(non_snake_case)]
union #raw_ident #impl_generics #where_clause {
#(
pub #variant_idents: ::core::mem::ManuallyDrop<
#variant_struct_idents #ty_generics,
>,
)*
}
#variants
fn #variant_fn_ident #impl_generics (
this: *mut #raw_ident #ty_generics,
) -> #variants_ident #ty_generics
#where_clause
{
match unsafe { *#discriminant_fn_ident(this) } {
#(#variants_arms,)*
}
}
})
}