Null-aware collection-for

[anqit]

Currently, for collection-for's on nullable collections, we need a null check:

List<int>? myInts = ...;

if (myInts != null) {
    for (final i in myInts) {
        // use i
    }
}

It would be nice if we could have a null-aware version of this syntax, something along the lines of

for(final i in myInts?) ...

or

for(final i in? myInts) ...

which would skip iteration if the iterable were null.

Sorry if this already exists and I'm just (null-)unaware of it :)

[lrhn]

It does not exist. I'm not sure it will.

One issue is that you should rarely have a nullable collection, it's better to use an empty collection, and not have two ways to represent "no elements".
Another is that they syntax could be better used for something else.

If we get Null-aware elements (#323), then you should be able to write:

 for (final i in [?myInts]) { ... }

and with a little luck and prodding, the compiler should be able to optimize that into:

if (myInts case final myInts?) for (final i in myInts) { ... }

(if you don't want to write that out yourself).

[anqit]

you should rarely have a nullable collection

while largely I agree, one situation I have run into this is optional function parameters.
Also, do you mind explaining or linking to whatever pattern-matching foo is happening here:
if (myInts case final myInts?) ..., I don't think I've seen that syntax before

[julemand101]

@anqit https://dart.dev/language/pattern-types#null-check

It matches if myInts are not null and it will define a new variable called myInts inside the scope of the if-statement which have a non-nullable type.