Inherit struct visibility on Unity class derive (#82)

This makes it so the derives for Unity classes automatically inherit the
visibility of the struct for all the methods and the binding struct.
This way you can have the structs in inner modules and still use them
from parent modules.

asr-derive/src/unity.rs

@@ -5,6 +5,8 @@ use syn::{Data, DeriveInput, Expr, ExprLit, Ident, Lit, Meta};
 pub fn process(input: TokenStream, mono_module: impl ToTokens) -> TokenStream {
     let ast: DeriveInput = syn::parse(input).unwrap();
 
+    let vis = ast.vis;
+
     let struct_data = match ast.data {
         Data::Struct(s) => s,
         _ => panic!("Only structs are supported"),
@@ -90,14 +92,14 @@ pub fn process(input: TokenStream, mono_module: impl ToTokens) -> TokenStream {
     };
 
     quote! {
-        struct #binding_name {
+        #vis struct #binding_name {
             class: #mono_module::Class,
             #static_table_field
             #(#field_names: u32,)*
         }
 
         impl #struct_name {
-            async fn bind(
+            #vis async fn bind(
                 process: &asr::Process,
                 module: &#mono_module::Module,
                 image: &#mono_module::Image,
@@ -117,11 +119,11 @@ pub fn process(input: TokenStream, mono_module: impl ToTokens) -> TokenStream {
         }
 
         impl #binding_name {
-            fn class(&self) -> &#mono_module::Class {
+            #vis fn class(&self) -> &#mono_module::Class {
                 &self.class
             }
 
-            fn read(&self, process: &asr::Process #maybe_instance_param) -> Result<#struct_name, ()> {
+            #vis fn read(&self, process: &asr::Process #maybe_instance_param) -> Result<#struct_name, ()> {
                 Ok(#struct_name {#(
                     #field_names: #field_reads,
                 )*})