Probable fix for unrepresentable concrete typedef.

engine/src/conversion/analysis/type_converter.rs

@@ -372,7 +372,10 @@ impl<'a> TypeConverter<'a> {
                 }
                 let (new_tn, api) = self.get_templated_typename(&Type::Path(typ))?;
                 extra_apis.extend(api.into_iter());
-                deps.remove(&tn);
+                // Although it's tempting to remove the dep on the original type,
+                // this means we wouldn't spot cases where the original type can't
+                // be represented in C++, e.g. because it has an unused template parameter.
+                // So we keep the original dep too.
                 typ = new_tn.to_type_path();
                 deps.insert(new_tn);
             }

engine/src/conversion/mod.rs

@@ -120,7 +120,7 @@ impl<'a> BridgeConverter<'a> {
                 Self::dump_apis("parsing", &apis);
                 // Inside parse_results, we now have a list of APIs.
                 // We now enter various analysis phases.
-                // Next, convert any typedefs.
+                // First, convert any typedefs.
                 // "Convert" means replacing bindgen-style type targets
                 // (e.g. root::std::unique_ptr) with cxx-style targets (e.g. UniquePtr).
                 let apis = convert_typedef_targets(self.config, apis);