presto-parser/src/main/java/io/prestosql/sql/tree/ExpressionTreeRewriter.java/ExpressionTreeRewriter/visitCurrentUser
class ExpressionTreeRewriter:        @Override
        protected Expression visitCurrentUser(CurrentUser node, Context<C> context)
        {
            if (!context.isDefaultRewrite()) {
                Expression result = rewriter.rewriteCurrentUser(node, context.get(), ExpressionTreeRewriter.this);
                if (result != null) {
                    return result;
                }
            }

            return node;
        }