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|
use quote::{format_ident, quote};
use crate::reflection::field::{generate as generate_field, ReflectionFieldGenOptions};
use crate::util::find_engine_crate_path;
const PRIMITIVE_REPRS: &[&'static str] = &[
"u8", "u16", "u32", "u64", "u128", "usize", "i8", "i16", "i32", "i64", "i128",
"isize",
];
pub fn generate(input: syn::ItemEnum) -> proc_macro2::TokenStream
{
let engine_crate_path = find_engine_crate_path().unwrap();
let input_ident = &input.ident;
let (impl_generics, type_generics, where_clause) = input.generics.split_for_impl();
let variant_lookup_match_arms =
input.variants.iter().enumerate().map(|(index, variant)| {
let variant_ident = &variant.ident;
let pattern = match variant.fields {
syn::Fields::Unit => quote! { Self::#variant_ident },
syn::Fields::Named(_) => quote! { Self::#variant_ident { .. } },
syn::Fields::Unnamed(_) => quote! { Self::#variant_ident(..) },
};
quote! {
#pattern => &enum_reflection.variants[#index]
}
});
let is_unit_only = input
.variants
.iter()
.all(|variant| matches!(variant.fields, syn::Fields::Unit));
let mod_name = format_ident!("__engine_private_{input_ident}");
let mut has_c_repr = false;
let mut primitive_repr: Option<proc_macro2::Ident> = None;
for attr in &input.attrs {
let syn::Meta::List(attr_meta) = &attr.meta else {
continue;
};
if !attr_meta.path.is_ident("repr") {
continue;
}
attr_meta
.parse_nested_meta(|nested_meta| {
let Some(meta_ident) = nested_meta.path.get_ident() else {
return Ok(());
};
if meta_ident == "C" {
has_c_repr = true;
} else if PRIMITIVE_REPRS.contains(&meta_ident.to_string().as_str()) {
primitive_repr = Some(meta_ident.clone());
} else {
return Err(nested_meta.error(concat!(
"Unsupported representation. ",
"Only C and primitive representations are allowed"
)));
}
Ok(())
})
.unwrap();
}
let mod_content = if is_unit_only {
quote! {}
} else {
if !has_c_repr && primitive_repr.is_none() {
panic!(concat!(
"Non unit-only enums must have a C or ",
"primitive representation to derive Reflection"
));
}
let variant_fields_structs = input.variants.iter().map(|variant| {
let fields = variant.fields.iter().map(|field| {
let field_type = &field.ty;
if let Some(field_ident) = &field.ident {
quote! { pub #field_ident: #field_type }
} else {
quote! { pub #field_type }
}
});
let ident = format_ident!("VariantFields{}", variant.ident);
match variant.fields {
syn::Fields::Named(_) => quote! {
#[repr(C)]
pub struct #ident { #(#fields),* }
},
syn::Fields::Unnamed(_) => quote! {
#[repr(C)]
pub struct #ident ( #(#fields),* );
},
syn::Fields::Unit => quote! {
#[repr(C)]
pub struct #ident;
},
}
});
let fields_union_fields = input.variants.iter().map(|variant| {
let variant_ident = &variant.ident;
let variant_fields_struct_ident =
format_ident!("VariantFields{}", variant.ident);
quote! {
pub #variant_ident: std::mem::ManuallyDrop<#variant_fields_struct_ident>
}
});
let discriminant_enum_variants = input.variants.iter().map(|variant| {
let variant_ident = &variant.ident;
if let Some((_, discriminant)) = &variant.discriminant {
quote! { #variant_ident = #discriminant }
} else {
quote! { #variant_ident }
}
});
// If the enum has both a C & primitive repr, the primitive repr must be used
let discriminant_enum_repr = if let Some(primitive_repr) = primitive_repr {
quote! { #primitive_repr }
} else if has_c_repr {
quote! { C }
} else {
unreachable!();
};
quote! {
#![allow(non_snake_case, dead_code)]
use super::*;
#[repr(C)]
pub struct Equivalent
{
pub tag: Discriminant,
pub payload: Fields
}
#[repr(#discriminant_enum_repr)]
pub enum Discriminant
{
#(#discriminant_enum_variants),*
}
#[repr(C)]
pub union Fields
{
#(#fields_union_fields),*
}
#(#variant_fields_structs)*
}
};
let variants = generate_variants(&input, &engine_crate_path);
quote! {
#[doc(hidden)]
mod #mod_name {
#mod_content
}
unsafe impl #impl_generics #engine_crate_path::reflection::Reflection for
#input_ident #type_generics #where_clause
{
const TYPE_REFLECTION: &#engine_crate_path::reflection::Type =
&const {
#engine_crate_path::reflection::Type::Enum(
#engine_crate_path::reflection::Enum {
variants: &[#(#variants),*],
is_unit_only: #is_unit_only
}
)
};
}
unsafe impl #impl_generics #engine_crate_path::reflection::EnumReflectionExt for
#input_ident #type_generics #where_clause
{
fn get_variant_reflection(&self)
-> &'static #engine_crate_path::reflection::EnumVariant
{
let enum_reflection = unsafe {
<Self as #engine_crate_path::reflection::Reflection>::TYPE_REFLECTION
.as_enum()
.unwrap_unchecked()
};
match self {
#(#variant_lookup_match_arms),*
}
}
}
}
}
fn generate_variants<'a>(
input: &'a syn::ItemEnum,
engine_crate_path: &'a syn::Path,
) -> impl Iterator<Item = proc_macro2::TokenStream> + use<'a>
{
let mod_name = format_ident!("__engine_private_{}", input.ident);
input.variants.iter().map(move |variant| {
let variant_name =
syn::LitStr::new(&variant.ident.to_string(), variant.ident.span());
let variant_ident = &variant.ident;
let variant_fields_struct_ident = format_ident!("VariantFields{}", variant.ident);
let fields = match &variant.fields {
syn::Fields::Unit => quote! { None },
syn::Fields::Named(named_fields) => {
let fields = named_fields.named.iter().enumerate().map(
|(variant_field_index, variant_field)| {
generate_field(
variant_field,
variant_field_index,
&engine_crate_path,
ReflectionFieldGenOptions {
field_vis_override: None,
gen_get_byte_offset: &|field| {
if let Some(field_ident) = &field.ident {
quote! {
std::mem::offset_of!(
#mod_name::Equivalent,
payload.#variant_ident
) +
std::mem::offset_of!(
#mod_name::#variant_fields_struct_ident,
#field_ident
)
}
} else {
unreachable!();
}
},
},
)
},
);
quote! {
Some(#engine_crate_path::reflection::EnumVariantFields::Named {
fields: &[#(#fields),*]
})
}
}
syn::Fields::Unnamed(unnamed_fields) => {
let fields = unnamed_fields.unnamed.iter().enumerate().map(
|(variant_field_index, variant_field)| {
generate_field(
variant_field,
variant_field_index,
&engine_crate_path,
ReflectionFieldGenOptions {
field_vis_override: None,
gen_get_byte_offset: &|field| {
if let Some(_) = &field.ident {
unreachable!()
} else {
let field_index =
proc_macro2::Literal::usize_unsuffixed(
variant_field_index,
);
quote! {
std::mem::offset_of!(
#mod_name::Equivalent,
payload.#variant_ident
) +
std::mem::offset_of!(
#mod_name::#variant_fields_struct_ident,
#field_index
)
}
}
},
},
)
},
);
quote! {
Some(#engine_crate_path::reflection::EnumVariantFields::Unnamed {
fields: &[#(#fields),*]
})
}
}
};
quote! {
#engine_crate_path::reflection::EnumVariant {
name: #variant_name,
fields: #fields
}
}
})
}
|
