presto-main/src/main/java/io/prestosql/operator/scalar/RowHashCodeOperator.java/RowHashCodeOperator/specialize
class RowHashCodeOperator:    @Override
    public ScalarFunctionImplementation specialize(BoundVariables boundVariables, int arity, Metadata metadata)
    {
        Type type = boundVariables.getTypeVariable("T");
        return new ScalarFunctionImplementation(
                false,
                ImmutableList.of(valueTypeArgumentProperty(RETURN_NULL_ON_NULL)),
                METHOD_HANDLE.bindTo(type));
    }