Suspicious code is added to UnboundLambda.WithNullableState function

[AlekseyTs]

Suspicious code is added to UnboundLambda.WithNullableState function here https://github.com/dotnet/roslyn/pull/40534/files#diff-b4c0d0abc290a3696848da779340f860R351:

        internal UnboundLambda WithNullableState(Binder binder, NullableWalker.VariableState nullableState)
        {
            var data = Data.WithCaching(true);
            var lambda = new UnboundLambda(Syntax, data, nullableState, HasErrors);
            data.SetUnboundLambda(lambda);
            return lambda;
        }

It looks like the data.SetUnboundLambda(lambda); line can change parent for an existing UnboundLambdaState instance, and the instance will be shared between two UnboundLambda instances.