Backport "Fix 0-dim broadcasting bug" to 0.9 (#177)

Author: mtfishman

Project.toml

@@ -1,7 +1,7 @@
 name = "BlockSparseArrays"
 uuid = "2c9a651f-6452-4ace-a6ac-809f4280fbb4"
 authors = ["ITensor developers <support@itensor.org> and contributors"]
-version = "0.9.4"
+version = "0.9.5"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"

src/blocksparsearrayinterface/broadcast.jl

@@ -63,7 +63,8 @@ end
 # which is logic that is handled by `fill!`.
 function copyto_blocksparse!(dest::AbstractArray, bc::Broadcasted{<:AbstractArrayStyle{0}})
   # `[]` is used to unwrap zero-dimensional arrays.
-  value = @allowscalar bc.f(bc.args...)[]
+  bcf = Broadcast.flatten(bc)
+  value = @allowscalar bcf.f(map(arg -> arg[], bcf.args)...)
   return @interface BlockSparseArrayInterface() fill!(dest, value)
 end