add offset tests

Author: mcabbott

base/abstractarray.jl

@@ -2622,7 +2622,7 @@ function _typed_stack(::Colon, ::Type{T}, ::Type{S}, A, Aax=_axes(A)) where {T,
     x1, _ = xit
     ax1 = _axes(x1)
     B = similar(_prototype(x1, A), T, ax1..., Aax...)
-    off = 1
+    off = firstindex(B)
     len = length(x1)
     while xit !== nothing
         x, state = xit

test/offsetarray.jl

@@ -802,6 +802,21 @@ end
     @test reshape(a, (:,)) === a
 end
 
+@testset "stack" begin
+    nought = OffsetArray([0, 0.1, 0.01], 0:2)
+    ten = OffsetArray([1,10,100,1000], 10:13)
+
+    @test stack(ten) == ten
+    @test stack(x^2 for x in ten) == ten.^2
+
+    @test axes(stack(nought for _ in ten)) == (0:2, 10:13)
+    @test axes(stack([nought for _ in ten])) == (0:2, 10:13)
+    @test axes(stack(nought for _ in ten; dims=1)) == (10:13, 0:2)
+    @test axes(stack((x, x^2) for x in nought)) == 1:2, 0:2
+    @test axes(stack(x -> x[end-1:end], ten for _ in nought, _ in nought)) == (1:2, 0:2, 0:2)
+    @test axes(stack([ten[end-1:end] for _ in nought, _ in nought])) == (1:2, 0:2, 0:2)
+end
+
 @testset "issue #41630: replace_ref_begin_end!/@view on offset-like arrays" begin
     x = OffsetArray([1 2; 3 4], -10:-9, 9:10)  # 2×2 OffsetArray{...} with indices -10:-9×9:10