public static <D> Expression<D> as(Expression<D> source, Path<D> alias) {
        return operation(alias.getType(), Ops.ALIAS, source, alias);
    }
Create an alias expression with the given source and alias

@param <D> type of expression
@param source source
@param alias alias
@return source as alias
querydsl-core/src/main/java/com/querydsl/core/types/ExpressionUtils.java