cover some more cases

compiler/src/main/cpp/capnpc-java.c++

@@ -1191,7 +1191,11 @@ private:
 
       bool isGeneric = false;
       {
-        auto type = field.getType().asList().getElementType();
+        auto type = field.getType();
+        while (type.isList()) {
+          type = type.asList().getElementType();
+        }
+
         if (type.isStruct()) {
           isGeneric = type.asStruct().getProto().getIsGeneric();
         }

compiler/src/test/schema/test.capnp

@@ -386,6 +386,11 @@ struct GenericMap(K, V)
     key @0 :K;
     value @1 :V;
   }
+
+ # Some other things that might cause problems.
+ a @1 :List(TestAllTypes);
+ b @2 :List(List(Entry));
+ c @3 :List(List(List(Entry)));
 }
 
 struct TestEmptyStruct {}