Support default SlotFragment implmentations

pyo3-macros-backend/src/pyimpl.rs

@@ -150,6 +150,9 @@ pub fn gen_default_slot_impls(cls: &syn::Ident, method_defs: Vec<TokenStream>) -
         .collect();
 
     let mut proto_impls = Vec::new();
+    let mut trait_impls = Vec::new();
+
+    let mut implemented_proto_fragments = HashSet::new();
 
     for meth in &mut method_defs {
         let options = PyFunctionOptions::from_attrs(&mut meth.attrs).unwrap();
@@ -158,15 +161,19 @@ pub fn gen_default_slot_impls(cls: &syn::Ident, method_defs: Vec<TokenStream>) -
                 let attrs = get_cfg_attributes(&meth.attrs);
                 proto_impls.push(quote!(#(#attrs)* #token_stream))
             }
-            GeneratedPyMethod::SlotTraitImpl(..) => {
-                todo!()
+            GeneratedPyMethod::SlotTraitImpl(method_name, token_stream) => {
+                implemented_proto_fragments.insert(method_name);
+                let attrs = get_cfg_attributes(&meth.attrs);
+                trait_impls.push(quote!(#(#attrs)* #token_stream));
             }
             GeneratedPyMethod::Method(_) | GeneratedPyMethod::TraitImpl(_) => {
                 panic!("Only protocol methods can have default implementation!")
             }
         }
     }
 
+    add_shared_proto_slots(&ty, &mut proto_impls, implemented_proto_fragments);
+
     quote! {
         impl #cls {
             #(#method_defs)*