DDC missing correct type check

[vsmenon]

This looks like a nasty regression - the following isn't throwing in DDC (but is in DDK) and is printing false:

void main() {
  List<int> l = [1, 2, 3].where((x) => x.isEven).map((x) => x + 1);
  print(l);
  print(l is List<int>);
}

It was working correctly as recently as 2.2.0-dev.1.1.

[vsmenon]

@nshahan - can you take a look? It's possible it's a recent analyzer change giving us the wrong type. The generated code for that example is checking against Iterable<int> not List<int> on the assignment to l.

fyi @jmesserly @stereotype441

[nshahan]

@vsmenon Yes, I'll dig in now.

[vsmenon]

Thanks! In reify_coercions.dart, there is a call to ast_properties.getImplicitCast(node) - may want to sanity check what type we're getting there on this example.

[vsmenon]

@stereotype441 - as discussed offline, we tracked to a CL by @scheglov . Will you folks be able to fix soon? This is a pretty nasty regression (soundness bug).

fyi - @jmesserly

[jmesserly]

https://dart-review.googlesource.com/c/sdk/+/97143 should fix it.

There may be a related (but distinct) issue in _findCovariantChecksForMember, for finding covariant parameter type checks. I haven't tried to write Dart code that demonstrates it in practice, but the implementation looks problematic.

It's not entirely obvious to me how to fix that one. I think it needs to be modified to use InheritanceManager2 (which has the nice side effect that it should run faster), but I'm not sure if there's a simple way to do that.