`sum(I -> A[I], CartesianIndices(A); dims=1)` needs initial value in order to work

[vargonis]

A = rand(3,4)
sum(I -> A[I], CartesianIndices(A); dims=1) # ERROR: BoundsError: attempt to access 3×4 Matrix{Float64} at index [0, 0]
sum(I -> A[I], CartesianIndices(A); dims=1, init=0.) # now it works

I'm running the following version:

julia> versioninfo()
Julia Version 1.10.4
Commit 48d4fd4 (2024-06-04 10:41 UTC)
Build Info:
Official https://julialang.org/ release
Platform Info:
OS: Linux (x86_64-linux-gnu)
CPU: 8 × 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-15.0.7 (ORCJIT, tigerlake)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)

[jishnub]

This also works:

julia> sum(I -> get(A, I, zero(eltype(A))), CartesianIndices(A); dims=1)
1×4 Matrix{Float64}:
 1.48551  1.92315  1.65579  1.628

The issue appears to be that the init is being computed as A[zero(CartesianIndex{2})], which throws the BoundsError