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use proc_macro::TokenStream;
use syn::{ItemFn, parse::Parse, Token, LitInt};
use quote::quote;
struct NativeFuncParams {
arity: LitInt,
variadic: Option<Token![..]>,
}
impl Parse for NativeFuncParams {
fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
let arity = input.parse()?;
let variadic = input.parse()?;
Ok(Self { arity , variadic })
}
}
#[proc_macro_attribute]
pub fn native_func(input: TokenStream, annotated_item: TokenStream) -> TokenStream {
let itemfn: ItemFn = syn::parse(annotated_item).expect("invalid rust function");
let input: NativeFuncParams = syn::parse(input).expect("invalid native fn annotation");
let arity = input.arity;
let variadic = input.variadic.is_some();
let visibility = itemfn.vis;
let block = itemfn.block;
let name = itemfn.sig.ident;
let name_str = name.to_string();
let inputs = itemfn.sig.inputs;
let output = itemfn.sig.output;
assert!(itemfn.sig.constness.is_none(), "item must not be const");
assert!(itemfn.sig.asyncness.is_none(), "item must not be async");
assert!(itemfn.sig.unsafety.is_none(), "item must not be unsafe");
assert!(itemfn.sig.abi.is_none(), "item must not contain an ABI specifier");
assert!(itemfn.sig.variadic.is_none(), "item must not be variadic");
let expanded = quote! {
#visibility fn #name() -> ::std::rc::Rc< ::matrix_lang::prelude::Function> {
::std::rc::Rc::new( ::matrix_lang::prelude::Function {
name: ::std::rc::Rc::from( #name_str ),
arity: #arity,
variadic: #variadic,
fun: ::matrix_lang::prelude::InnerFunction::Native(
::std::rc::Rc::new(
|#inputs| #output #block
)
)
})
}
};
TokenStream::from(expanded)
}
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