rust procedural macro to generate symbol resolver helper functions

procmacro.rs

extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro2::{Ident, Span};
use syn::{ItemType, LitStr};
use quote::quote;

#[proc_macro_attribute]
pub fn hello(_attr: TokenStream, item: TokenStream) -> TokenStream {
    let input = syn::parse_macro_input!(item as ItemType);

    let fn_name_str = format!("resolve_{}", input.ident);
    let fn_name = Ident::new(&fn_name_str, Span::call_site());
    let fn_type = input.ty.clone();
    let fn_name_lit_str = LitStr::new(&fn_name_str, Span::call_site());

    let result = quote! {
        #input
        unsafe fn #fn_name() -> Option<#fn_type> {
            unimplemented!()
        }
    };

    result.into()
}