@Specialization
public NilPlaceholder initialize(RubyHash hash, RubyProc block) {
hash.initialize(block);
return NilPlaceholder.INSTANCE;
}
@Specialization
public NilPlaceholder initialize(
RubyHash hash, @SuppressWarnings("unused") UndefinedPlaceholder block) {
hash.initialize(null);
return NilPlaceholder.INSTANCE;
}