use NoLabel as default blocklabel

Author: ogauthe

NDTensors/src/lib/GradedAxes/src/fusion.jl

@@ -5,6 +5,7 @@ struct OneToOne{T} <: AbstractUnitRange{T} end
 OneToOne() = OneToOne{Bool}()
 Base.first(a::OneToOne) = one(eltype(a))
 Base.last(a::OneToOne) = one(eltype(a))
+BlockArrays.blockaxes(::OneToOne{Bool}) = (Block.(OneToOne()),)
 
 # https://github.com/ITensor/ITensors.jl/blob/v0.3.57/NDTensors/src/lib/GradedAxes/src/tensor_product.jl
 # https://en.wikipedia.org/wiki/Tensor_product

NDTensors/src/lib/GradedAxes/src/gradedunitrange.jl

@@ -19,6 +19,7 @@ using BlockArrays:
   findblockindex,
   mortar
 using Compat: allequal
+using FillArrays: Fill
 using ..LabelledNumbers:
   LabelledNumbers, LabelledInteger, LabelledUnitRange, label, labelled, unlabel
 
@@ -38,7 +39,9 @@ function Base.OrdinalRange{T,T}(a::GradedOneTo{<:LabelledInteger{T}}) where {T}
 end
 
 # == is just a range comparison that ignores labels. Need dedicated function to check equality.
-blocklabels(::AbstractUnitRange) = nothing
+struct NoLabel end
+blocklabels(r::AbstractUnitRange) = Fill(NoLabel(), blocklength(r))
+
 function labelled_isequal(a1::AbstractUnitRange, a2::AbstractUnitRange)
   return blockisequal(a1, a2) && (blocklabels(a1) == blocklabels(a2))
 end