Revert missing to nothings

#232 was found to be a huge mistake. For interface checks, you want `nothing` instead of `missing` because you want to handle the cases. The issue with `missing` is that it propagates, `missing + 1 == missing`. We don't want that here, we want clear and precise error messages at the spot where the `nothing` is found if it's not supposed to be there and it's supposed to be handled. That is antithetical to most of its usage here. So this is a strong revert with a breaking update, which should fix downstream libraries (LoopVectorization, OrdinaryDiffEq, etc.) which were never received the proper downstream PRs from the original change anyways.

Project.toml

@@ -1,6 +1,6 @@
 name = "ArrayInterface"
 uuid = "4fba245c-0d91-5ea0-9b3e-6abc04ee57a9"
-version = "4.0.4"
+version = "5.0.0"
 
 [deps]
 Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"

docs/src/index.md

@@ -44,7 +44,7 @@ julia> ArrayInterface.size(a)
 (static(1), 3)
 
 julia> ArrayInterface.known_size(typeof(a))
-(1, missing)
+(1, nothing)
 
 ```
 
@@ -62,8 +62,8 @@ Methods should avoid forcing conversion to static sizes when dynamic sizes could
 Fore example, `fxn(x) = _fxn(Static.static(ArrayInterface.size(x)), x)` would result in dynamic dispatch if `x` is an instance of `Matrix`.
 Additionally, `ArrayInterface.size` should only be used outside of generated functions to avoid possible world age issues.
 
-Generally, `ArrayInterface.size` uses the return of `known_size` to form a static value for those dimensions with known length and only queries dimensions corresponding to `missing`.
-For example, the previous example had a known size of `(1, missing)`.
+Generally, `ArrayInterface.size` uses the return of `known_size` to form a static value for those dimensions with known length and only queries dimensions corresponding to `nothing`.
+For example, the previous example had a known size of `(1, nothing)`.
 Therefore, `ArrayInterface.size` would have compile time information about the first dimension returned as `static(1)` and would only look up the size of the second dimension at run time.
 This means the above example `ArrayInterface.size(a)` would lower to code similar to this at compile time: `Static.StaticInt(1), Base.arraysize(x, 1)`.
 Generic support for `ArrayInterface.known_size` relies on calling `known_length` for each type returned from `axes_types`.
@@ -108,13 +108,13 @@ ArrayInterface.dimnames(::StaticDimnames{dnames}) where {dnames} = static(dnames
 struct DynamicDimnames{N}
     dimnames::NTuple{N,Symbol}
 end
-ArrayInterface.known_dimnames(::Type{DynamicDimnames{N}}) where {N} = ntuple(_-> missing, Val(N))
+ArrayInterface.known_dimnames(::Type{DynamicDimnames{N}}) where {N} = ntuple(_-> nothing, Val(N))
 ArrayInterface.dimnames(x::DynamicDimnames) = getfield(x, :dimnames)
 
 ```
 
-Notice that `DynamicDimnames` returns `missing` instead of a symbol for each dimension.
-This indicates dimension names are present for `DynamicDimnames` but that information is missing at compile time.
+Notice that `DynamicDimnames` returns `nothing` instead of a symbol for each dimension.
+This indicates dimension names are present for `DynamicDimnames` but that information is nothing at compile time.
 
 Dimension names should be appropriately propagated between nested arrays using `ArrayInterface.to_parent_dims`. 
 This allows types such as `SubArray` and `PermutedDimsArray` to work with named dimensions.
@@ -166,7 +166,7 @@ using ArrayInterface: axes_types, parent_type, to_dims
     for dim in 1:ndims(A)
         # offset relative to parent array
         O = relative_known_offsets(A, dim)
-        if O === missing  # offset is not known at compile time and is an `Int`
+        if O === nothing  # offset is not known at compile time and is an `Int`
             push!(out.args, :(IdOffsetRange{Int, axes_types($P, $(static(dim)))}))
         else # offset is known, therefore it is a `StaticInt`
             push!(out.args, :(IdOffsetRange{StaticInt{$O}, axes_types($P, $(static(dim))}))

src/ArrayInterface.jl

@@ -81,10 +81,10 @@ buffer(x::SparseMatrixCSC) = getfield(x, :nzval)
 buffer(x::SparseVector) = getfield(x, :nzval)
 
 """
-    known_length(::Type{T}) -> Union{Int,Missing}
+    known_length(::Type{T}) -> Union{Int,Nothing}
 
 If `length` of an instance of type `T` is known at compile time, return it.
-Otherwise, return `missing`.
+Otherwise, return `nothing`.
 """
 known_length(x) = known_length(typeof(x))
 known_length(::Type{<:NamedTuple{L}}) where {L} = length(L)
@@ -94,7 +94,7 @@ known_length(::Type{<:Number}) = 1
 known_length(::Type{<:AbstractCartesianIndex{N}}) where {N} = N
 known_length(::Type{T}) where {T} = _maybe_known_length(Base.IteratorSize(T), T)
 _maybe_known_length(::Base.HasShape, ::Type{T}) where {T} = prod(known_size(T))
-_maybe_known_length(::Base.IteratorSize, ::Type) = missing
+_maybe_known_length(::Base.IteratorSize, ::Type) = nothing
 function known_length(::Type{<:Iterators.Flatten{I}}) where {I}
     known_length(I) * known_length(eltype(I))
 end
@@ -415,10 +415,10 @@ Indicates the most efficient way to access elements from the collection in low-l
 For `GPUArrays`, will return `ArrayInterface.GPU()`.
 For `AbstractArray` supporting a `pointer` method, returns `ArrayInterface.CPUPointer()`.
 For other `AbstractArray`s and `Tuple`s, returns `ArrayInterface.CPUIndex()`.
-Otherwise, returns `missing`.
+Otherwise, returns `nothing`.
 """
 device(A) = device(typeof(A))
-device(::Type) = missing
+device(::Type) = nothing
 device(::Type{<:Tuple}) = CPUTuple()
 device(::Type{T}) where {T<:Array} = CPUPointer()
 device(::Type{T}) where {T<:AbstractArray} = _device(has_parent(T), T)
@@ -597,7 +597,7 @@ end
 
 function Base.length(A::AbstractArray2)
     len = known_length(A)
-    if len === missing
+    if len === nothing
         return Int(prod(size(A)))
     else
         return Int(len)
@@ -1136,7 +1136,7 @@ function __init__()
             Static.eachop_tuple(_offset_axis_type, Static.nstatic(Val(ndims(T))), ArrayInterface.parent_type(T))
         end
         function ArrayInterface.known_offsets(::Type{A}) where {A<:OffsetArrays.OffsetArray}
-            ntuple(identity -> missing, Val(ndims(A)))
+            ntuple(identity -> nothing, Val(ndims(A)))
         end
         function ArrayInterface.offsets(A::OffsetArrays.OffsetArray)
             map(+, ArrayInterface.offsets(parent(A)), relative_offsets(A))

src/axes.jl

@@ -41,7 +41,7 @@ function axes_types(::Type{T}) where {T<:PermutedDimsArray}
     eachop_tuple(field_type, to_parent_dims(T), axes_types(parent_type(T)))
 end
 function axes_types(::Type{T}) where {T<:AbstractRange}
-    if known_length(T) === missing
+    if known_length(T) === nothing
         return Tuple{OneTo{Int}}
     else
         return Tuple{SOneTo{known_length(T)}}
@@ -62,7 +62,7 @@ end
 function _non_reshaped_axis_type(::Type{A}, d::StaticInt{D}) where {A,D}
     paxis = axes_types(parent_type(A), d)
     if D === 1
-        if known_length(paxis) === missing
+        if known_length(paxis) === nothing
             return paxis
         else
             return SOneTo{div(known_length(paxis) * sizeof(eltype(parent_type(A))), sizeof(eltype(A)))}
@@ -191,7 +191,7 @@ end
 # For now we just make sure the linear elements are accurate.
 parent_type(::Type{LazyAxis{:,P}}) where {P<:Array} = OneTo{Int}
 @inline function parent_type(::Type{LazyAxis{:,P}}) where {P}
-    if known_length(P) === missing
+    if known_length(P) === nothing
         return OptionallyStaticUnitRange{StaticInt{1},Int}
     else
         return SOneTo{known_length(P)}
@@ -208,14 +208,14 @@ known_first(::Type{LazyAxis{N,P}}) where {N,P} = known_offsets(P, static(N))
 known_first(::Type{LazyAxis{:,P}}) where {P} = 1
 Base.firstindex(x::LazyAxis) = first(x)
 @inline function Base.first(x::LazyAxis{N})::Int where {N}
-    if known_first(x) === missing
+    if known_first(x) === nothing
         return Int(offsets(parent(x), static(N)))
     else
         return Int(known_first(x))
     end
 end
 @inline function Base.first(x::LazyAxis{:})::Int
-    if known_first(x) === missing
+    if known_first(x) === nothing
         return first(parent(x))
     else
         return known_first(x)
@@ -225,20 +225,20 @@ known_last(::Type{LazyAxis{N,P}}) where {N,P} = known_last(axes_types(P, static(
 known_last(::Type{LazyAxis{:,P}}) where {P} = known_length(P)
 Base.lastindex(x::LazyAxis) = last(x)
 Base.last(x::LazyAxis) = _last(known_last(x), x)
-_last(::Missing, x) = last(parent(x))
+_last(::Nothing, x) = last(parent(x))
 _last(N::Int, x) = N
 
 known_length(::Type{LazyAxis{N,P}}) where {N,P} = known_size(P, static(N))
 known_length(::Type{LazyAxis{:,P}}) where {P} = known_length(P)
 @inline function Base.length(x::LazyAxis{N})::Int where {N}
-    if known_length(x) === missing
+    if known_length(x) === nothing
         return size(getfield(x, :parent), static(N))
     else
         return known_length(x)
     end
 end
 @inline function Base.length(x::LazyAxis{:})::Int
-    if known_length(x) === missing
+    if known_length(x) === nothing
         return length(parent(x))
     else
         return known_length(x)
@@ -254,7 +254,7 @@ Base.axes1(x::Slice{<:LazyAxis}) = indices(parent(x.indices))
 Base.to_shape(x::LazyAxis) = length(x)
 
 @inline function Base.checkindex(::Type{Bool}, x::LazyAxis, i::Integer)
-    if known_first(x) === missing || known_last(x) === missing
+    if known_first(x) === nothing || known_last(x) === nothing
         return checkindex(Bool, parent(x), i)
     else  # everything is static so we don't have to retrieve the axis
         return (!(known_first(x) > i) || !(known_last(x) < i))

src/dimensions.jl

@@ -160,8 +160,8 @@ _is_named(x::NTuple{N,Symbol}) where {N} = x !== _nunderscore(Val(N))
 _is_named(::Any) = true
 
 """
-    known_dimnames(::Type{T}) -> Tuple{Vararg{Union{Symbol,Missing}}}
-    known_dimnames(::Type{T}, dim::Union{Int,StaticInt}) -> Union{Symbol,Missing}
+    known_dimnames(::Type{T}) -> Tuple{Vararg{Union{Symbol,Nothing}}}
+    known_dimnames(::Type{T}, dim::Union{Int,StaticInt}) -> Union{Symbol,Nothing}
 
 Return the names of the dimensions for `x`. `:_` is used to indicate a dimension does not
 have a name.
@@ -229,7 +229,7 @@ An error is thrown if any keywords are used which do not occur in `nda`'s names.
 
 1. parse into static dimnension names and key words.
 2. find each dimnames in key words
-3. if missing is found use Colon()
+3. if nothing is found use Colon()
 4. if (ndims - ncolon) === nkwargs then all were found, else error
 =#
 @generated function find_all_dimnames(x::Tuple{Vararg{Any,ND}}, nd::Tuple{Vararg{Any,NI}}, inds::Tuple, default) where {ND,NI}

src/indexing.jl

@@ -277,7 +277,7 @@ previously executed `to_index(old_axis, arg) -> index`. `to_axis` assumes that
 """
 @inline function to_axis(axis, inds)
     if !can_change_size(axis) &&
-       (known_length(inds) !== missing && known_length(axis) === known_length(inds))
+       (known_length(inds) !== nothing && known_length(axis) === known_length(inds))
         return axis
     else
         return to_axis(IndexStyle(axis), axis, inds)

src/ranges.jl

@@ -1,16 +1,16 @@
 
 _cartesian_index(i::Tuple{Vararg{Int}}) = CartesianIndex(i)
-_cartesian_index(::Any) = missing
+_cartesian_index(::Any) = nothing
 
 """
-    known_first(::Type{T}) -> Union{Int,Missing}
+    known_first(::Type{T}) -> Union{Int,Nothing}
 
 If `first` of an instance of type `T` is known at compile time, return it.
-Otherwise, return `missing`.
+Otherwise, return `nothing`.
 
 ```julia
 julia> ArrayInterface.known_first(typeof(1:4))
-missing
+nothing
 
 julia> ArrayInterface.known_first(typeof(Base.OneTo(4)))
 1
@@ -19,7 +19,7 @@ julia> ArrayInterface.known_first(typeof(Base.OneTo(4)))
 known_first(x) = known_first(typeof(x))
 function known_first(::Type{T}) where {T}
     if parent_type(T) <: T
-        return missing
+        return nothing
     else
         return known_first(parent_type(T))
     end
@@ -30,14 +30,14 @@ function known_first(::Type{T}) where {N,R,T<:CartesianIndices{N,R}}
 end
 
 """
-    known_last(::Type{T}) -> Union{Int,Missing}
+    known_last(::Type{T}) -> Union{Int,Nothing}
 
 If `last` of an instance of type `T` is known at compile time, return it.
-Otherwise, return `missing`.
+Otherwise, return `nothing`.
 
 ```julia
 julia> ArrayInterface.known_last(typeof(1:4))
-missing
+nothing
 
 julia> ArrayInterface.known_first(typeof(static(1):static(4)))
 4
@@ -47,7 +47,7 @@ julia> ArrayInterface.known_first(typeof(static(1):static(4)))
 known_last(x) = known_last(typeof(x))
 function known_last(::Type{T}) where {T}
     if parent_type(T) <: T
-        return missing
+        return nothing
     else
         return known_last(parent_type(T))
     end
@@ -57,14 +57,14 @@ function known_last(::Type{T}) where {N,R,T<:CartesianIndices{N,R}}
 end
 
 """
-    known_step(::Type{T}) -> Union{Int,Missing}
+    known_step(::Type{T}) -> Union{Int,Nothing}
 
 If `step` of an instance of type `T` is known at compile time, return it.
-Otherwise, return `missing`.
+Otherwise, return `nothing`.
 
 ```julia
 julia> ArrayInterface.known_step(typeof(1:2:8))
-missing
+nothing
 
 julia> ArrayInterface.known_step(typeof(1:4))
 1
@@ -74,7 +74,7 @@ julia> ArrayInterface.known_step(typeof(1:4))
 known_step(x) = known_step(typeof(x))
 function known_step(::Type{T}) where {T}
     if parent_type(T) <: T
-        return missing
+        return nothing
     else
         return known_step(parent_type(T))
     end
@@ -215,21 +215,21 @@ known_last(::Type{<:OptionallyStaticUnitRange{<:Any,StaticInt{L}}}) where {L} =
 known_last(::Type{<:OptionallyStaticStepRange{<:Any,<:Any,StaticInt{L}}}) where {L} = L::Int
 
 @inline function Base.first(r::OptionallyStaticRange)::Int
-    if known_first(r) === missing
+    if known_first(r) === nothing
         return getfield(r, :start)
     else
         return known_first(r)
     end
 end
 function Base.step(r::OptionallyStaticStepRange)::Int
-    if known_step(r) === missing
+    if known_step(r) === nothing
         return getfield(r, :step)
     else
         return known_step(r)
     end
 end
 @inline function Base.last(r::OptionallyStaticRange)::Int
-    if known_last(r) === missing
+    if known_last(r) === nothing
         return getfield(r, :stop)
     else
         return known_last(r)
@@ -306,9 +306,9 @@ end
 
 @noinline unequal_error(x,y) = @assert false "Unequal Indices: x == $x != $y == y"
 @inline check_equal(x, y) = x == y || unequal_error(x,y)
-_try_static(::Missing, ::Missing) = missing
-_try_static(x::Int, ::Missing) = x
-_try_static(::Missing, y::Int) = y
+_try_static(::Nothing, ::Nothing) = nothing
+_try_static(x::Int, ::Nothing) = x
+_try_static(::Nothing, y::Int) = y
 @inline _try_static(::StaticInt{N}, ::StaticInt{N}) where {N} = StaticInt{N}()
 @inline function _try_static(::StaticInt{M}, ::StaticInt{N}) where {M,N}
     @assert false "Unequal Indices: StaticInt{$M}() != StaticInt{$N}()"
@@ -330,7 +330,7 @@ Base.lastindex(x::OptionallyStaticRange) = length(x)
     end
 end
 Base.length(r::OptionallyStaticStepRange) = _range_length(first(r), step(r), last(r))
-_range_length(start, s, stop) = missing
+_range_length(start, s, stop) = nothing
 @inline function _range_length(start::Int, s::Int, stop::Int)
    if s > 0
         if stop < start  # isempty

src/size.jl

@@ -56,7 +56,7 @@ size(a::Array, dim::Integer) = Base.arraysize(a, convert(Int, dim))
 function size(a::A, dim::Integer) where {A}
     if parent_type(A) <: A
         len = known_size(A, dim)
-        if len === missing
+        if len === nothing
             return Int(length(axes(a, dim)))
         else
             return StaticInt(len)
@@ -77,10 +77,10 @@ size(x::Iterators.Zip) = Static.reduce_tup(promote_shape, map(size, getfield(x,
 
 """
     known_size(::Type{T}) -> Tuple
-    known_size(::Type{T}, dim) -> Union{Int,Missing}
+    known_size(::Type{T}, dim) -> Union{Int,Nothing}
 
 Returns the size of each dimension of `A` or along dimension `dim` of `A` that is known at
-compile time. If a dimension does not have a known size along a dimension then `missing` is
+compile time. If a dimension does not have a known size along a dimension then `nothing` is
 returned in its position.
 """
 known_size(x) = known_size(typeof(x))
@@ -98,10 +98,10 @@ end
 
 # 1. `Zip` doesn't check that its collections are compatible (same size) at construction,
 #   but we assume as much b/c otherwise it will error while iterating. So we promote to the
-#   known size if matching a `Missing` and `Int` size.
+#   known size if matching a `Nothing` and `Int` size.
 # 2. `promote_shape(::Tuple{Vararg{CanonicalInt}}, ::Tuple{Vararg{CanonicalInt}})` promotes
 #   trailing dimensions (which must be of size 1), to `static(1)`. We want to stick to
-#   `Missing` and `Int` types, so we do one last pass to ensure everything is dynamic
+#   `Nothing` and `Int` types, so we do one last pass to ensure everything is dynamic
 @inline function known_size(::Type{<:Iterators.Zip{T}}) where {T}
     dynamic(reduce_tup(_promote_shape, eachop(_unzip_size, nstatic(Val(known_length(T))), T)))
 end