BitArray is documented to be a DenseArray

[eschnett]

The documentation of BitArray claims that it is a subtype of DenseArray (file bitarray.jl) in its documentation, but the type declaration makes it only a subtype of AbstractArray. I don't know which is correct (probably the code...), but the inconsistency should be resolved.

[mbauman]

Ah, whoops, that's a documentation bug. They were indeed previously DenseArrays, but that was a problem: #25858. My mistake for missing the doc portion of the change.

[mbauman]

Sorry for stealing the #good-first-issue… I figured I'd clean up my own mess.