as_if function

[HungMingWu]

Hi Mike,
I have an idea

void  process(const Statement& stmt)
{
    if (StatementList::isKind(stmt.kind)) {
       auto &liststmt = stmt.as<StatementList>();
    } else if (BlockStatement::isKind(stmt.kind) {
       auto &blockstmt= stmt.as<BlockStatement>();
    } else {
       // ignore
    }
}

If we have a function as_if, similar to std::get_if
The above code would become

void  process(const Statement& stmt)
{
    if (auto liststmt = stmt.as_if<StatementList>()) {
    } else if (auto blockstmt = stmt.as_if<BlockStatement>()) {
    } else {
       // ignore
    }
}

The idea can extend to Symbol and Expression
How do you think?

[MikePopoloski]

Sure, that seems useful to me.

[HungMingWu]

OK, I would implement the feature

[MikePopoloski]

Sounds good, thanks!