Consider marking spread dangerous

There are quite a few serious open issues with spread that don’t look like being solved any time soon. They probably won’t affect most people (I personally don’t ever expect to be affected by them), but it’s very easy to be affected by them.

If rest is independently solid, then perhaps split spreadRest into rest and dangerousSpread; if it’s not, then dangerousSpreadRest.

The issue names no files, tests, or entry points. Review how spread and rest are handled, then examine the serious open spread issues referenced by the report; done would require an agreed approach for marking the relevant spread behavior as dangerous, including whether to use dangerousSpread or dangerousSpreadRest.

Written by the indexing model from the issue text.