presto-main/src/main/java/io/prestosql/sql/relational/VariableReferenceExpression.java/VariableReferenceExpression/VariableReferenceExpression
class VariableReferenceExpression:    public VariableReferenceExpression(String name, Type type)
    {
        this.name = requireNonNull(name, "name is null");
        this.type = requireNonNull(type, "type is null");
    }