BitArrays should not be DenseArrays

BitArray has previously been subtype of DenseArray, making it defined as a StridedArray. However - BitArrays do not and can not support the `pointer` function. As such, they can never be passed to a C function in the same manner that all other StridedArrays can.

This patch makes `BitArray <: AbstractArray`. Surprisingly little breaks in our test set, but this is indeed massively breaking.  Notably, most of the other changes required here were actually long-standing bugs that this change simply happened to uncover.

NEWS.md

@@ -262,6 +262,9 @@ This section lists changes that do not have deprecation warnings.
  `Tridiagonal{T,V<:AbstractVector{T}}` and `SymTridiagonal{T,V<:AbstractVector{T}}`
  respectively ([#22718], [#22925], [#23035], [#23154]).
 
+ * The immediate supertype of `BitArray` is now simply `AbstractArray`. `BitArray` is no longer
+ considered a subtype of `DenseArray` and `StridedArray` ([#25857]).
+
  * When called with an argument that contains `NaN` elements, `findmin` and `findmax` now return the
  first `NaN` found and its corresponding index. Previously, `NaN` elements were ignored.
  The new behavior matches that of `min`, `max`, `minimum`, and `maximum`.

base/bitarray.jl

@@ -9,7 +9,7 @@
 
 Space-efficient `N`-dimensional boolean array, which stores one bit per boolean value.
 """
-mutable struct BitArray{N} <: DenseArray{Bool, N}
+mutable struct BitArray{N} <: AbstractArray{Bool, N}
  chunks::Vector{UInt64}
  len::Int
  dims::NTuple{N,Int}
@@ -657,6 +657,9 @@ indexoffset(::Colon) = 0
  fill_chunks!(B.chunks, y, f0, l0)
  return B
 end
+@propagate_inbounds function setindex!(B::BitArray, X::AbstractArray, J0::Union{Colon,UnitRange{Int}})
+ _setindex!(IndexStyle(B), B, X, to_indices(B, (J0,))[1])
+end
 
 # logical indexing
 

base/multidimensional.jl

@@ -1462,7 +1462,7 @@ end
 # contiguous multidimensional indexing: if the first dimension is a range,
 # we can get some performance from using copy_chunks!
 
-@inline function setindex!(B::BitArray, X::StridedArray, J0::Union{Colon,UnitRange{Int}})
+@inline function setindex!(B::BitArray, X::Union{StridedArray,BitArray}, J0::Union{Colon,UnitRange{Int}})
  I0 = to_indices(B, (J0,))[1]
  @boundscheck checkbounds(B, I0)
  l0 = length(I0)
@@ -1473,13 +1473,13 @@ end
  return B
 end
 
-@inline function setindex!(B::BitArray, X::StridedArray,
+@inline function setindex!(B::BitArray, X::Union{StridedArray,BitArray},
  I0::Union{Colon,UnitRange{Int}}, I::Union{Int,UnitRange{Int},Colon}...)
  J = to_indices(B, (I0, I...))
  @boundscheck checkbounds(B, J...)
  _unsafe_setindex!(B, X, J...)
 end
-@generated function _unsafe_setindex!(B::BitArray, X::StridedArray,
+@generated function _unsafe_setindex!(B::BitArray, X::Union{StridedArray,BitArray},
  I0::Union{Slice,UnitRange{Int}}, I::Union{Int,UnitRange{Int},Slice}...)
  N = length(I)
  quote
@@ -1520,6 +1520,11 @@ end
  @boundscheck checkbounds(B, J...)
  _unsafe_setindex!(B, x, J...)
 end
+@propagate_inbounds function setindex!(B::BitArray, X::AbstractArray,
+ I0::Union{Colon,UnitRange{Int}}, I::Union{Int,UnitRange{Int},Colon}...)
+ _setindex!(IndexStyle(B), B, X, to_indices(B, (I0, I...))...)
+end
+
 @generated function _unsafe_setindex!(B::BitArray, x,
  I0::Union{Slice,UnitRange{Int}}, I::Union{Int,UnitRange{Int},Slice}...)
  N = length(I)
@@ -1601,17 +1606,13 @@ for (V, PT, BT) in [((:N,), BitArray, BitArray), ((:T,:N), Array, StridedArray)]
  checkdims_perm(P, B, perm)
 
  #calculates all the strides
+ native_strides = size_to_strides(1, size(B)...)
  strides_1 = 0
- @nexprs $N d->(strides_{d+1} = stride(B, perm[d]))
+ @nexprs $N d->(strides_{d+1} = native_strides[perm[d]])
 
  #Creates offset, because indexing starts at 1
  offset = 1 - sum(@ntuple $N d->strides_{d+1})
 
- if isa(B, SubArray)
- offset += first_index(B::SubArray) - 1
- B = B.parent
- end
-
  ind = 1
  @nexprs 1 d->(counts_{$N+1} = strides_{$N+1}) # a trick to set counts_($N+1)
  @nloops($N, i, P,

test/bitarray.jl

@@ -1491,3 +1491,11 @@ end
 end
 
 timesofar("I/O")
+
+@testset "not strided" begin
+ @test_throws ErrorException pointer(trues(1))
+ @test_throws ErrorException pointer(trues(1),1)
+ b = falses(3)
+ b[:] = view(trues(10), [1,3,7])
+ @test b == trues(3)
+end