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#![deny(clippy::all, clippy::pedantic)]
use proc_macro::TokenStream;
use quote::{ToTokens, format_ident, quote};
use syn::{Item, LitStr, Path as SynPath, parse};
macro_rules! syn_path {
($first_segment: ident $(::$segment: ident)*) => {
::syn::Path {
leading_colon: None,
segments: ::syn::punctuated::Punctuated::from_iter([
syn_path_segment!($first_segment),
$(syn_path_segment!($segment),)*
])
}
};
}
macro_rules! syn_path_segment {
($segment: ident) => {
::syn::PathSegment {
ident: ::proc_macro2::Ident::new(
stringify!($segment),
::proc_macro2::Span::call_site(),
),
arguments: ::syn::PathArguments::None,
}
};
}
#[proc_macro_derive(Reflection)]
pub fn reflection_derive(input: TokenStream) -> TokenStream
{
let input = parse::<Item>(input).unwrap();
let input = match input {
Item::Struct(input) => input,
Item::Enum(_) => unimplemented!(),
_ => panic!("Invalid input"),
};
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 fields = input.fields.into_iter().enumerate().map(|(index, field)| {
let field_ident = field.ident.unwrap_or_else(|| format_ident!("{index}"));
let field_type = &field.ty;
let field_name = LitStr::new(&field_ident.to_string(), field_ident.span());
// since std::any::type_name as const is not stable yet
let field_type_name = field_type.to_token_stream().to_string();
quote! {
#engine_crate_path::reflection::StructField {
name: #field_name,
index: #index,
layout: std::alloc::Layout::new::<#field_type>(),
byte_offset: std::mem::offset_of!(Self, #field_ident),
type_id: std::any::TypeId::of::<#field_type>(),
type_name: #field_type_name,
get_type: #engine_crate_path::reflection::FnWithDebug::new(|| {
struct SpecializationTarget<Field>(std::marker::PhantomData<Field>);
trait FieldHasReflection
{
fn field_type_reflection(&self)
-> Option<&'static #engine_crate_path::reflection::Type>;
}
trait FieldDoesNotHaveReflection
{
fn field_type_reflection(&self)
-> Option<&'static #engine_crate_path::reflection::Type>;
}
impl<Field> FieldDoesNotHaveReflection for &SpecializationTarget<Field>
{
fn field_type_reflection(&self)
-> Option<&'static #engine_crate_path::reflection::Type>
{
None
}
}
impl<Field> FieldHasReflection for SpecializationTarget<Field>
where
Field: #engine_crate_path::reflection::Reflection
{
fn field_type_reflection(&self)
-> Option<&'static #engine_crate_path::reflection::Type>
{
Some(Field::type_reflection())
}
}
(&SpecializationTarget::<#field_type>(std::marker::PhantomData))
.field_type_reflection()
})
}
}
});
quote! {
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::Struct(
#engine_crate_path::reflection::Struct {
fields: &[
#(#fields),*
]
}
)
};
}
}
.into()
}
fn find_engine_crate_path() -> Option<SynPath>
{
let cargo_crate_name = std::env::var("CARGO_CRATE_NAME").ok()?;
let cargo_pkg_name = std::env::var("CARGO_PKG_NAME").ok()?;
if cargo_pkg_name == "engine" && cargo_crate_name != "engine" {
// Macro is used by a crate example/test/benchmark
return Some(syn_path!(engine));
}
if cargo_crate_name == "engine" {
return Some(syn_path!(crate));
}
Some(syn_path!(engine))
}
|
