invariant_booleans doesn't understand list manipulation (or that getters aren't invariant)

[Hixie]

Consider:

void test(List<double> x) {
  if (x.length == 1)
    return;
  x.add(1.0);
  if (x.length == 1) // bogus invariant_booleans error
    return;
  x.removeLast();
  if (x.length == 1) // bogus invariant_booleans error
    return;
}

More generally it doesn't seem to understand that getters aren't invariant:

class Test {
  int _value = 0;
  int get value	{
    _value += 1;
    return _value;
  }
}

void test(Test x) {
  if (x.value == 0)
    return;
  if (x.value == 0) // bogus invariant_booleans error
    return;
}

There's a number of other invariant_booleans errors on file.

[srawlins]

The real list of invariant_booleans bugs is this list of 19.

The maturity state of this lint rule has thus been marked "experimental". http://dart-lang.github.io/linter/lints/invariant_booleans.html

[jamesderlin]

I feel like this is equivalent to #57884. In general, it seems that the analyzer does not consider that function calls might mutate variables. Or maybe it does but assumes that local variables can't be modified?

Here's yet another example that came up when I was trying to write some string parsing code:

final list = [1, 2, 3];
final iterator = list.iterator..moveNext();
if (iterator.current == 1) {
  iterator.moveNext();
  if (iterator.current == 1) { // bogus invariant_booleans error
    print('foo');
  }
}

[srawlins]

We've deprecated invariant_booleans and will not be fixing correctness bugs going forward.