Type instability in axes(arr,dim)

[jishnub]

The method returns an IdOffsetRange or a Base.OneTo depending on whether the value of dim is less than ndims(arr). For example:

julia> a = OffsetVector(rand(3),-1:1);

julia> @code_warntype axes(a,1)
Variables
  #self#::Core.Compiler.Const(axes, false)
  A::OffsetArray{Float64,1,Array{Float64,1}}
  d::Int64

Body::Union{Base.OneTo{Int64}, OffsetArrays.IdOffsetRange{Int64,Base.OneTo{Int64}}}
1 ─       nothing
│   %2  = OffsetArrays.ndims(A)::Core.Compiler.Const(1, false)
│   %3  = (d <= %2)::Bool
└──       goto #3 if not %3
2 ─ %5  = OffsetArrays.parent(A)::Array{Float64,1}
│   %6  = OffsetArrays.axes(%5, d)::Base.OneTo{Int64}
│   %7  = Base.getproperty(A, :offsets)::Tuple{Int64}
│   %8  = Base.getindex(%7, d)::Int64
│   %9  = OffsetArrays.IdOffsetRange(%6, %8)::OffsetArrays.IdOffsetRange{Int64,Base.OneTo{Int64}}
└──       return %9
3 ─ %11 = Base.OneTo::Core.Compiler.Const(Base.OneTo, false)
│   %12 = (%11)(1)::Core.Compiler.Const(Base.OneTo(1), false)
└──       return %12

Perhaps this might return an IdOffsetRange in each case?

[jishnub]

The line is

OffsetArrays.jl/src/OffsetArrays.jl

Line 95 in 7294f3d

@inline Base.axes(A::OffsetArray, d) = d <= ndims(A) ? IdOffsetRange(axes(parent(A), d), A.offsets[d]) : Base.OneTo(1)