[solved] Null check with `?` gives analyzer warning, but `!` is accepted

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1 
    final graph = switch (widget.type) {
      CollectionGraphType.watchCollection => manager.breakdown,
      CollectionGraphType.wristTime => manager.wristTime,
    };

    childKeys = graph.value?
            .map((e) => GlobalKey(debugLabel: e.label))
            .toList() ??
        [];

Gives me the linter error “Conditions must have a static type of ‘bool’ at the ? after value.
Try changing the condition”

value is of type ValueNotifier<List<GraphSegmentDto>?> if I replace the ? with ! it works.

2

Is it maybe because ValueNotifier is a generic, so it becomes nullable if its T is nullable (which it is in your case). Its not surprising that ! makes it work as doing that you are force casting it to be non null.

3

But why doesn’t the? Work then and why thinks the analyser that it’s part of a tertiary expression?

4

Are you trying to write graph.value ?. map( … ?

If so, I don’t think you can put a space between the ? and .

5

Oh right! I see what you mean now. Yes that is strange!

6

It’s not too strange. You can’t put whitespace inside an identifier or between the < and = of <=. :slight_smile:

7

Randal do you mean the newline after the graph.value? ?

8

Actually there is no newline the formatter put it like that. And it works if I replace the ? With a ! Which should have the same problem

9

If the formatter split a ?. operator, the formatter has a bug. But it should work fine with ?. as long as you make sure there’s no space in there.

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10

thanks, indeed it was the formatting. We are performing a pretty big refactoring and somehow the formatter doesn’t format some of the files.

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11

BTW, I believe ?. is set up as a single token due to plans for a convenient dot syntax in the near future :slight_smile:

dart-lang/language#3685

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