Fix broadcast_indices

This fixes a regression introduced in 4f1b479. broadcast_indices() needs to
be overloaded by packages for custom types, so it cannot be hidden under
_broadcast_indices(). Also, ::Type is incorrect since the method only applies
to scalars.

Make the tests more complex to be closer to actual implementations in packages
so that regressions like this will be noticed in the future.

base/broadcast.jl

@@ -45,12 +45,12 @@ promote_containertype(::Type{T}, ::Type{T}) where {T} = T
 ## Calculate the broadcast indices of the arguments, or error if incompatible
 # array inputs
 broadcast_indices() = ()
-broadcast_indices(A) = _broadcast_indices(containertype(A), A)
+broadcast_indices(A) = broadcast_indices(containertype(A), A)
 @inline broadcast_indices(A, B...) = broadcast_shape(broadcast_indices(A), broadcast_indices(B...))
-_broadcast_indices(::Type, A) = ()
-_broadcast_indices(::Type{Tuple}, A) = (OneTo(length(A)),)
-_broadcast_indices(::Type{Array}, A::Ref) = ()
-_broadcast_indices(::Type{Array}, A) = indices(A)
+broadcast_indices(::ScalarType, A) = ()
+broadcast_indices(::Type{Tuple}, A) = (OneTo(length(A)),)
+broadcast_indices(::Type{Array}, A::Ref) = ()
+broadcast_indices(::Type{Array}, A) = indices(A)
 
 # shape (i.e., tuple-of-indices) inputs
 broadcast_shape(shape::Tuple) = shape

test/broadcast.jl

@@ -419,6 +419,7 @@ struct Array19745{T,N} <: AbstractArray{T,N}
     data::Array{T,N}
 end
 Base.getindex(A::Array19745, i::Integer...) = A.data[i...]
+Base.setindex!(A::Array19745, v::Any, i::Integer...) = setindex!(A.data, v, i...)
 Base.size(A::Array19745) = size(A.data)
 
 Base.Broadcast._containertype{T<:Array19745}(::Type{T}) = Array19745
@@ -435,8 +436,12 @@ Base.Broadcast.broadcast_indices(::Type{Array19745}, A::Ref) = ()
 getfield19745(x::Array19745) = x.data
 getfield19745(x)             = x
 
-Base.Broadcast.broadcast_c(f, ::Type{Array19745}, A, Bs...) =
-    Array19745(Base.Broadcast.broadcast_c(f, Array, getfield19745(A), map(getfield19745, Bs)...))
+function Base.Broadcast.broadcast_c(f, ::Type{Array19745}, A, Bs...)
+    T     = Base.Broadcast._broadcast_eltype(f, A, Bs...)
+    shape = Base.Broadcast.broadcast_indices(A, Bs...)
+    dest = Array19745(Array{T}(Base.index_lengths(shape...)))
+    return broadcast!(f, dest, A, Bs...)
+end
 
 @testset "broadcasting for custom AbstractArray" begin
     a  = randn(10)