This reminds me of pattern matching. I'm not sure if the pattern matching proposal allows this, though. Rust would allow something like:

if let Some(x) = some_optional {
  ...
}

We propose a new variant of the if statement that fuses a condition declaration with an indirection in the true branch.  We call it an 'indirect if statement'.

I find it a bit odd that this only works for unary `operator*`. I want this to be more general, but I don't know if there's a good alternative without going for full pattern matching.

An indirect if statement of the form:

    if (DECL : EXPR) X else Y;

is equivalent to:

    {
        auto&& __c = EXPR;
        if (__c) {
            DECL = *__c;
            X;
        } else {
            Y;  // noteworthy: DECL is not in scope here
        }
    }

It would sometimes be preferable to forward __c into DECL, but sometimes not. E.g. if EXPR returned an optional<vector<...>> and DECL wanted to be a value and not a reference. I don't know what the right choice is.

I do know that I'd use this if it was in the language.

--Justin