1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49

#![recursion_limit = "128"]
extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro2::TokenStream as TokenStream2;
use quote::quote;
use syn::{parse_macro_input, DeriveInput};

/// A macro to derive empty actor implementations
///
/// Use this macro if you only care about the component model mechanics for your type.
///
/// Implementations derived using this macro have message type `Never` (or `!` if you prefer).
/// Whenever they receive a network message, they simply log a warning.
#[proc_macro_derive(Actor)]
pub fn actor(input: TokenStream) -> TokenStream {
    // Parse the input stream
    let ast = parse_macro_input!(input as DeriveInput);

    // Build the impl
    let gen = impl_actor(&ast);

    //println!("Derived code:\n{}", gen.clone().into_string());

    // Return the generated impl
    gen.into()
}

fn impl_actor(ast: &syn::DeriveInput) -> TokenStream2 {
    let name = &ast.ident;
    if let syn::Data::Struct(_) = ast.data {
        let generics = &ast.generics;
        let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();

        quote! {
            impl #impl_generics ActorRaw for #name #ty_generics #where_clause {

                type Message = Never;

                fn receive(&mut self, env: MsgEnvelope<Self::Message>) -> Handled {
                    warn!(self.log(), "Got msg, but component isn't handling any: {:?}", env);
                    Handled::Ok
                }
            }
        }
    } else {
        //Nope. This is an Enum. We cannot handle these!
        panic!("#[derive(Actor)] is only defined for structs, not for enums!");
    }
}