> For example, another way to think of this is that you have a buffer of initialized memory (no unsafe), containing a view onto some piece of data, from which you serve a subset to the user, but you get the format of the subset wrong, so that parts of the view leak through. That's a bleed.

If there's full initialization then this is just a logic error, no? Apart from some kind of capability typing over ranges of bytes (not very ergonomic), this would be a very difficult subtype of "bleed" to statically describe, much less prevent.