[BUG] broadcast on `BlockVector{LabelledInteger}` is broken

[ogauthe]

using BlockArrays: Block, mortar
using GradedArrays.GradedUnitRanges: gradedrange
using GradedArrays.SymmetrySectors: U1

indices = mortar([[Block(1)]])
v = gradedrange([U1(1) => 1])[indices]
Int.(v)

ERROR: MethodError: no method matching subblocks(::BlockVector{Int64, Vector{…}, Tuple{…}}, ::Tuple{GradedArrays.GradedUnitRanges.GradedOneTo{…}}, ::Int64)
The function `subblocks` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  subblocks(::AbstractArray, ::NTuple{N, AbstractUnitRange{Int64}}, ::Integer) where N
   @ BlockArrays ~/Documents/itensor/BlockArrays.jl/src/blockbroadcast.jl:119
  subblocks(::Any, ::NTuple{N, AbstractUnitRange{Int64}}, ::Integer) where N
   @ BlockArrays ~/Documents/itensor/BlockArrays.jl/src/blockbroadcast.jl:116

Stacktrace:
 [1] (::BlockArrays.var"#58#63"{BlockVector{…}, Base.Broadcast.Broadcasted{…}, Tuple{…}})(dim::Int64)
   @ BlockArrays ~/Documents/itensor/BlockArrays.jl/src/blockbroadcast.jl:149
 [2] ntuple
   @ ./ntuple.jl:19 [inlined]
 [3] _generic_blockbroadcast_copyto!(dest::BlockVector{…}, bc::Base.Broadcast.Broadcasted{…})
   @ BlockArrays ~/Documents/itensor/BlockArrays.jl/src/blockbroadcast.jl:148
 [4] copyto!(dest::BlockVector{…}, bc::Base.Broadcast.Broadcasted{…})
   @ BlockArrays ~/Documents/itensor/BlockArrays.jl/src/blockbroadcast.jl:189
 [5] copy
   @ ./broadcast.jl:897 [inlined]
 [6] materialize(bc::Base.Broadcast.Broadcasted{BlockArrays.BlockStyle{1}, Nothing, Type{Int64}, Tuple{BlockVector{…}}})
   @ Base.Broadcast ./broadcast.jl:872
 [7] top-level scope
   @ REPL[7]:1
Some type information was truncated. Use `show(err)` to see complete types.

The cause is a restriction to Int eltype in BlockArrays.jl, specifically in

# BlockArrays.jl/src/blockbroadcast.jl:119
function subblocks(arr::AbstractArray, bs::NTuple{N,AbstractUnitRange{Int}}, dim::Integer) where N

and

# BlockArrays.jl/src/blockbroadcast.jl:103
SubBlockIterator(arr::AbstractArray, bs::NTuple{N,AbstractUnitRange{Int}}, dim::Integer) where N

@mtfishman you already worked on such restrictions in JuliaArrays/BlockArrays.jl#405. Do you have an idea if there is a specific reason for these restrictions? I can make a PR to BlockArrays.jl to remove them.

[mtfishman]

I don't see a reason for those restrictions, it sounds like it would be a good PR to generalize those definitions.

[ogauthe]

fixed by JuliaArrays/BlockArrays.jl#455