Should be nothing

Author: Tokazama

src/ArrayInterface.jl

@@ -36,7 +36,7 @@ known_length(x) = known_length(typeof(x))
 known_length(::Type{<:NTuple{N,<:Any}}) where {N} = N
 known_length(::Type{<:NamedTuple{L}}) where {L} = length(L)
 known_length(::Type{T}) where {T<:Base.Slice} = known_length(parent_type(T))
-known_length(::Type{T}) where {T} = false
+known_length(::Type{T}) where {T} = nothing
 
 """
     can_change_size(::Type{T}) -> Bool