Should NegativeBuckets of ExponentialHistogram be made public?

[utpilla]

The spec currently says that Histogram.Record should only be used for non-negative values. However, the spec also mentions how to deal with negative values in case of ExponentialHistograms. The current implementation of ExponentialHistogram does process negative values and puts them into NegativeBuckets.

Do we want to make NegativeBuckets available to exporters considering we should also not expect people to use Histogram.Record for negative values?

[utpilla]

FYI @alanwest

I spoke to @reyang and it looks like the spec might be updated in the future to allow for negative values in this case. I think we could mark NegativeBuckets internal for now and make it public once the spec changes.

Found a related issue: open-telemetry/opentelemetry-specification#2715