Don't instantiate abstract types when they are returned from stubs

This is less agressive than the original solution of not instantating
abstract types in ci_lazy_methods at all. This is done to minimize the
changes this PR introduces.

Author: thk123

jbmc/src/java_bytecode/ci_lazy_methods_needed.cpp

@@ -52,11 +52,6 @@ void ci_lazy_methods_neededt::add_all_needed_classes(
   const pointer_typet &pointer_type)
 {
   namespacet ns{symbol_table};
-  const java_class_typet &underlying_type =
-    to_java_class_type(ns.follow(pointer_type.subtype()));
-
-  if(underlying_type.is_abstract())
-    return;
 
   initialize_instantiated_classes_from_pointer(pointer_type, ns);
 

jbmc/src/java_bytecode/java_bytecode_language.cpp

@@ -1045,7 +1045,17 @@ bool java_bytecode_languaget::convert_single_method(
     const pointer_typet *pointer_return_type =
       type_try_dynamic_cast<pointer_typet>(function_type.return_type()))
   {
-    needed_lazy_methods->add_all_needed_classes(*pointer_return_type);
+    // If the return type is abstract, we won't forcibly instantiate it here
+    // otherwise this can cause abstract methods to be explictly called
+    // TODO(tkiley): Arguably no abstract class should ever be added to
+    // TODO(tkiley): ci_lazy_methods_neededt, but this needs further
+    // TODO(tkiley): investigation
+    namespacet ns{symbol_table};
+    const java_class_typet &underlying_type =
+      to_java_class_type(ns.follow(pointer_return_type->subtype()));
+
+    if(!underlying_type.is_abstract())
+      needed_lazy_methods->add_all_needed_classes(*pointer_return_type);
   }
 
   return true;