Make zero on array of arrays apply recursively

NEWS.md

@@ -35,6 +35,7 @@ New library features
 --------------------
 * `replace(string, pattern...)` now supports an optional `IO` argument to
   write the output to a stream rather than returning a string ([#48625]).
+* `zero(::AbstractArray)` now applies recursively, so `zero([[1,2],[3,4,5]])` now produces `[[0,0],[0,0,0]]` rather than erroring [#38064].
 
 Standard library changes
 ------------------------

base/abstractarray.jl

@@ -1198,7 +1198,8 @@ function copymutable(a::AbstractArray)
 end
 copymutable(itr) = collect(itr)
 
-zero(x::AbstractArray{T}) where {T} = fill!(similar(x, typeof(zero(T))), zero(T))
+zero(x::AbstractArray{T}) where {T<:Number} = fill!(similar(x, typeof(zero(T))), zero(T))
+zero(x::AbstractArray) = map(zero, x)
 
 ## iteration support for arrays by iterating over `eachindex` in the array ##
 # Allows fast iteration by default for both IndexLinear and IndexCartesian arrays

test/abstractarray.jl

@@ -1860,3 +1860,14 @@ f45952(x) = [x;;]
     @test_throws "invalid index: true of type Bool" isassigned(A, 1, true)
     @test_throws "invalid index: true of type Bool" isassigned(A, true)
 end
+
+@testset "zero" begin
+    @test zero([1 2; 3 4]) isa Matrix{Int}
+    @test zero([1 2; 3 4]) == [0 0; 0 0]
+
+    @test zero([1.0]) isa Vector{Float64}
+    @test zero([1.0]) == [0.0]
+
+    @test zero([[2,2], [3,3,3]]) isa Vector{Vector{Int}}
+    @test zero([[2,2], [3,3,3]]) == [[0,0], [0, 0, 0]]
+end