Syntax to allow assignment operator other than = on null

[Thaina]

Simply put, we might have nullable number. Operator assignment cannot be used there

int? x = null;
x += 1; // null here

I think we should allow ?? to work on the left side of =

int? x = null;
x ?? 0 += 1; // 1 here

The problem here is we might have long chain of member access to use operator assignment

Normally we need to do it like this

user.financeNullableDictionary["income"] = user.financeNullableDictionary["income"] ?? 0;
user.financeNullableDictionary["income"] += 10000; 
// or
user.financeNullableDictionary["income"] = (user.financeNullableDictionary["income"] ?? 0) + 10000; 

It should be shorter with ??

user.financeNullableDictionary["income"] ?? 0 += 10000;

But it should not work in this case

user?.financeNullableDictionary?["income"] ?? 0 += 10000; // Should error?

[orthoxerox]

Why not

int? x = null;
x ??= 0;
x += 1;

If compound assignments become lvalues, you will be able to write x ??= 0 += 1

[Thaina]

I'm not sure but I already think that x ??= 0 += 1 will became x ??= 1 because rightmost = would be solved first