julia> CartesianIndices()
ERROR: MethodError: no method matching CartesianIndices()
The type `CartesianIndices` exists, but no method is defined for this combination of argument types when trying to construct it.

Closest candidates are:
  CartesianIndices(::Tuple{})
   @ Base multidimensional.jl:271
  CartesianIndices(::AbstractArray)
   @ Base multidimensional.jl:281
  CartesianIndices(::R) where {N, R<:NTuple{N, OrdinalRange{Int64, Int64}}}
   @ Base multidimensional.jl:268
  ...

Stacktrace:
 [1] top-level scope
   @ REPL[9]:1
 [2] top-level scope
   @ none:1

julia> CartesianIndices(2, 2)
ERROR: MethodError: no method matching CartesianIndices(::Int64, ::Int64)
The type `CartesianIndices` exists, but no method is defined for this combination of argument types when trying to construct it.

Closest candidates are:
  CartesianIndices(::Tuple{})
   @ Base multidimensional.jl:271
  CartesianIndices(::AbstractArray)
   @ Base multidimensional.jl:281
  CartesianIndices(::R) where {N, R<:NTuple{N, OrdinalRange{Int64, Int64}}}
   @ Base multidimensional.jl:268
  ...

Stacktrace:
 [1] top-level scope
   @ REPL[12]:1
 [2] top-level scope
   @ none:1

julia> CartesianIndices(1:2, 1:2)
ERROR: MethodError: no method matching CartesianIndices(::UnitRange{Int64}, ::UnitRange{Int64})
The type `CartesianIndices` exists, but no method is defined for this combination of argument types when trying to construct it.

Closest candidates are:
  CartesianIndices(::AbstractArray)
   @ Base multidimensional.jl:281
  CartesianIndices(::Tuple{})
   @ Base multidimensional.jl:271
  CartesianIndices(::R) where {N, R<:NTuple{N, OrdinalRange{Int64, Int64}}}
   @ Base multidimensional.jl:268
  ...

Stacktrace:
 [1] top-level scope
   @ REPL[13]:1
 [2] top-level scope
   @ none:1

julia> CartesianIndices(())
CartesianIndices(())

julia> CartesianIndices((2, 2))
CartesianIndices((2, 2))

julia> CartesianIndices((1:2, 1:2))
CartesianIndices((1:2, 1:2))

julia> using BlockArrays

julia> collect(BlockRange(blockedrange([2, 3])))
5-element Vector{Block{1, Int64}}:
 Block(1)
 Block(2)
 Block(3)
 Block(4)
 Block(5)

julia> collect(BlockRange(mortar([1:2, 3:5])))
2-element Vector{Block{1, Int64}}:
 Block(1)
 Block(2)