make Some type a zero-dim broadcast container (e.g. a scalar)

Replaces #35778
Replaces #39184
Fixes #39151
Refs #35675
Refs #43200

Author: vtjnash

NEWS.md

@@ -82,6 +82,8 @@ Standard library changes
 * TCP socket objects now expose `closewrite` functionality and support half-open mode usage ([#40783]).
 * Intersect returns a result with the eltype of the type-promoted eltypes of the two inputs ([#41769]).
 * `Iterators.countfrom` now accepts any type that defines `+`. ([#37747])
+* `Some`containers now support broadcast as zero dimensional immutable containers. `Some(x)`
+   should be preferred to `Ref(x)` when you wish to exempt `x` from broadcasting ([#35778]).
 
 #### InteractiveUtils
 * A new macro `@time_imports` for reporting any time spent importing packages and their dependencies ([#41612])

base/broadcast.jl

@@ -614,8 +614,9 @@ Base.@propagate_inbounds Base.getindex(bc::Broadcasted) = bc[CartesianIndex(())]
 
 Index into `A` with `I`, collapsing broadcasted indices to their singleton indices as appropriate.
 """
-Base.@propagate_inbounds _broadcast_getindex(A::Union{Ref,AbstractArray{<:Any,0},Number}, I) = A[] # Scalar-likes can just ignore all indices
+Base.@propagate_inbounds _broadcast_getindex(A::Union{Ref,Some,AbstractArray{<:Any,0},Number}, I) = A[] # Scalar-likes can just ignore all indices
 Base.@propagate_inbounds _broadcast_getindex(::Ref{Type{T}}, I) where {T} = T
+Base.@propagate_inbounds _broadcast_getindex(::Some{Type{T}}, I) where {T} = T
 # Tuples are statically known to be singleton or vector-like
 Base.@propagate_inbounds _broadcast_getindex(A::Tuple{Any}, I) = A[1]
 Base.@propagate_inbounds _broadcast_getindex(A::Tuple, I) = A[I[1]]
@@ -661,6 +662,20 @@ Base.@propagate_inbounds function _broadcast_getindex(bc::Broadcasted{<:Any,<:An
     args = _getindex(tail(tail(bc.args)), I)
     return _broadcast_getindex_evalf(bc.f, T, S, args...)
 end
+Base.@propagate_inbounds function _broadcast_getindex(bc::Broadcasted{<:Any,<:Any,<:Any,<:Tuple{Some{Type{T}},Vararg{Any}}}, I) where {T}
+    args = _getindex(tail(bc.args), I)
+    return _broadcast_getindex_evalf(bc.f, T, args...)
+end
+Base.@propagate_inbounds function _broadcast_getindex(bc::Broadcasted{<:Any,<:Any,<:Any,<:Tuple{Any,Some{Type{T}},Vararg{Any}}}, I) where {T}
+    arg1 = _broadcast_getindex(bc.args[1], I)
+    args = _getindex(tail(tail(bc.args)), I)
+    return _broadcast_getindex_evalf(bc.f, arg1, T, args...)
+end
+Base.@propagate_inbounds function _broadcast_getindex(bc::Broadcasted{<:Any,<:Any,<:Any,<:Tuple{Some{Type{T}},Some{Type{S}},Vararg{Any}}}, I) where {T,S}
+    args = _getindex(tail(tail(bc.args)), I)
+    return _broadcast_getindex_evalf(bc.f, T, S, args...)
+end
+
 
 # Utilities for _broadcast_getindex
 Base.@propagate_inbounds _getindex(args::Tuple, I) = (_broadcast_getindex(args[1], I), _getindex(tail(args), I)...)
@@ -691,15 +706,15 @@ julia> Broadcast.broadcastable([1,2,3]) # like `identity` since arrays already s
  3
 
 julia> Broadcast.broadcastable(Int) # Types don't support axes, indexing, or iteration but are commonly used as scalars
-Base.RefValue{Type{Int64}}(Int64)
+Base.Some{Type{Int64}}(Int64)
 
 julia> Broadcast.broadcastable("hello") # Strings break convention of matching iteration and act like a scalar instead
-Base.RefValue{String}("hello")
+Base.Some{String}("hello")
 ```
 """
-broadcastable(x::Union{Symbol,AbstractString,Function,UndefInitializer,Nothing,RoundingMode,Missing,Val,Ptr,AbstractPattern,Pair,IO}) = Ref(x)
-broadcastable(::Type{T}) where {T} = Ref{Type{T}}(T)
-broadcastable(x::Union{AbstractArray,Number,AbstractChar,Ref,Tuple,Broadcasted}) = x
+broadcastable(x::Union{Symbol,AbstractString,Function,UndefInitializer,Nothing,RoundingMode,Missing,Val,Ptr,AbstractPattern,Pair,IO}) = Some(x)
+broadcastable(::Type{T}) where {T} = Some{Type{T}}(T)
+broadcastable(x::Union{AbstractArray,Number,AbstractChar,Some,Ref,Tuple,Broadcasted}) = x
 # Default to collecting iterables — which will error for non-iterables
 broadcastable(x) = collect(x)
 broadcastable(::Union{AbstractDict, NamedTuple}) = throw(ArgumentError("broadcasting over dictionaries and `NamedTuple`s is reserved"))
@@ -722,7 +737,7 @@ combine_eltypes(f, args::Tuple) =
 """
     broadcast(f, As...)
 
-Broadcast the function `f` over the arrays, tuples, collections, [`Ref`](@ref)s and/or scalars `As`.
+Broadcast the function `f` over the arrays, tuples, collections, [`Some`](@ref)s and/or scalars `As`.
 
 Broadcasting applies the function `f` over the elements of the container arguments and the
 scalars themselves in `As`. Singleton and missing dimensions are expanded to match the
@@ -781,7 +796,7 @@ julia> abs.((1, -2))
 julia> broadcast(+, 1.0, (0, -2.0))
 (1.0, -1.0)
 
-julia> (+).([[0,2], [1,3]], Ref{Vector{Int}}([1,-1]))
+julia> (+).([[0,2], [1,3]], Some{Vector{Int}}([1,-1]))
 2-element Vector{Vector{Int64}}:
  [1, 1]
  [2, 2]

base/some.jl

@@ -1,22 +1,39 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
 """
-    Some{T}
+    Some{T} <: AbstractArray{T,0}
 
 A wrapper type used in `Union{Some{T}, Nothing}` to distinguish between the absence
 of a value ([`nothing`](@ref)) and the presence of a `nothing` value (i.e. `Some(nothing)`).
 
 Use [`something`](@ref) to access the value wrapped by a `Some` object.
 """
-struct Some{T}
+struct Some{T} <: AbstractArray{T,0}
     value::T
 end
 
 Some(::Type{T}) where {T} = Some{Type{T}}(T)
 
-promote_rule(::Type{Some{T}}, ::Type{Some{S}}) where {T, S<:T} = Some{T}
+eltype(x::Type{<:Some{T}}) where {T} = @isdefined(T) ? T : Any
+size(x::Some) = ()
+axes(x::Some) = ()
+length(x::Some) = 1
+isempty(x::Some) = false
+ndims(x::Some) = 0
+ndims(::Type{<:Some}) = 0
+iterate(r::Some) = (r.value, nothing)
+getindex(r::Some) = r.value
+iterate(r::Some, s) = nothing
+IteratorSize(::Type{<:Some}) = HasShape{0}()
 
 nonnothingtype(::Type{T}) where {T} = typesplit(T, Nothing)
+function nonnothingtype_checked(T::Type)
+    R = nonnothingtype(T)
+    R >: T && error("could not compute non-nothing type")
+    return R
+end
+
+promote_rule(::Type{Some{T}}, ::Type{Some{S}}) where {T, S<:T} = Some{T}
 promote_rule(T::Type{Nothing}, S::Type) = Union{S, Nothing}
 function promote_rule(T::Type{>:Nothing}, S::Type)
     R = nonnothingtype(T)
@@ -26,12 +43,6 @@ function promote_rule(T::Type{>:Nothing}, S::Type)
     return Union{R, Nothing}
 end
 
-function nonnothingtype_checked(T::Type)
-    R = nonnothingtype(T)
-    R >: T && error("could not compute non-nothing type")
-    return R
-end
-
 convert(::Type{T}, x::T) where {T>:Nothing} = x
 convert(::Type{T}, x) where {T>:Nothing} = convert(nonnothingtype_checked(T), x)
 convert(::Type{Nothing}, x) = throw(MethodError(convert, (Nothing, x)))

test/broadcast.jl

@@ -427,6 +427,13 @@ end
 @test (+).(Ref(1), Ref(2)) == 3
 @test (+).([[0,2], [1,3]], Ref{Vector{Int}}([1,-1])) == [[1,1], [2,2]]
 
+# Some as 0-dimensional array for broadcast
+@test (-).(C_NULL, C_NULL)::UInt == 0
+@test (+).(1, Some(2)) == 3
+@test (+).(Some(1), Some(2)) == 3
+@test (+).([[0,2], [1,3]], Some{Vector{Int}}([1,-1])) == [[1,1], [2,2]]
+
+
 # Check that broadcast!(f, A) populates A via independent calls to f (#12277, #19722),
 # and similarly for broadcast!(f, A, numbers...) (#19799).
 @test let z = 1; A = broadcast!(() -> z += 1, zeros(2)); A[1] != A[2]; end
@@ -573,6 +580,11 @@ let io = IOBuffer()
     broadcast(x -> print(io, x), [Ref(1.0)])
     @test String(take!(io)) == "Base.RefValue{Float64}(1.0)"
 end
+@test getindex.([Some(1), Some(2)]) == [1, 2]
+let io = IOBuffer()
+    broadcast(x -> print(io, x), [Some(1.0)])
+    @test String(take!(io)) == "Some(1.0)"
+end
 
 # Test that broadcast's promotion mechanism handles closures accepting more than one argument.
 # (See issue #19641 and referenced issues and pull requests.)
@@ -635,7 +647,7 @@ end
     @test broadcast(foo, "x", [1, 2, 3]) == ["hello", "hello", "hello"]
 
     @test isequal(
-        [Set([1]), Set([2])] .∪ Ref(Set([3])),
+        [Set([1]), Set([2])] .∪ Some(Set([3])),
         [Set([1, 3]), Set([2, 3])])
 end
 
@@ -916,7 +928,7 @@ end
     @test reduce(paren, bcraw) == foldl(paren, xs)
 
     # issue #41055
-    bc = Broadcast.instantiate(Broadcast.broadcasted(Base.literal_pow, Ref(^), [1,2], Ref(Val(2))))
+    bc = Broadcast.instantiate(Broadcast.broadcasted(Base.literal_pow, Some(^), [1,2], Some(Val(2))))
     @test sum(bc, dims=1, init=0) == [5]
     bc = Broadcast.instantiate(Broadcast.broadcasted(*, ['a','b'], 'c'))
     @test prod(bc, dims=1, init="") == ["acbc"]