restore Base.similar behavior

Author: jlchan

src/vector_of_array.jl

@@ -712,9 +712,22 @@ Base.eltype(::Type{<:AbstractVectorOfArray{T}}) where {T} = T
     end
 end
 @inline function Base.similar(VA::VectorOfArray, ::Type{T} = eltype(VA)) where {T}
-    VectorOfArray(similar.(Base.parent(VA), T))
+    VectorOfArray([similar(VA[:, i], T) for i in eachindex(VA.u)])
 end
 
+# for VectorOfArray with multi-dimensional parent arrays of arrays where all elements are the same type
+function Base.similar(vec::VectorOfArray{
+        T, N, AT}) where {T, N, AT <: AbstractArray{<:AbstractArray{T}}}
+    return VectorOfArray(similar.(Base.parent(vec)))
+end
+
+# special-case when the multi-dimensional parent array is just an AbstractVector (call the old method)
+function Base.similar(vec::VectorOfArray{
+        T, N, AT}) where {T, N, AT <: AbstractVector{<:AbstractArray{T}}}
+    return Base.similar(vec, eltype(vec))
+end
+
+
 # fill!
 # For DiffEqArray it ignores ts and fills only u
 function Base.fill!(VA::AbstractVectorOfArray, x)