Always return a value in 1-d circshift! of abstractarray.jl (#53554)

Co-authored-by: Sukera <11753998+Seelengrab@users.noreply.github.com>
Co-authored-by: Mosè Giordano <giordano@users.noreply.github.com>

Author: 3 people

base/abstractarray.jl

@@ -3656,9 +3656,9 @@ end
 ## 1-d circshift ##
 function circshift!(a::AbstractVector, shift::Integer)
     n = length(a)
-    n == 0 && return
+    n == 0 && return a
     shift = mod(shift, n)
-    shift == 0 && return
+    shift == 0 && return a
     l = lastindex(a)
     reverse!(a, firstindex(a), l-shift)
     reverse!(a, l-shift+1, lastindex(a))

test/arrayops.jl

@@ -797,6 +797,14 @@ end
     oa = OffsetVector(copy(a), -1)
     @test circshift!(oa, 1) === oa
     @test oa == circshift(OffsetVector(a, -1), 1)
+
+    # 1d circshift! (#53554)
+    a = []
+    @test circshift!(a, 1) === a
+    @test circshift!(a, 1) == []
+    a = [1:5;]
+    @test circshift!(a, 10) === a
+    @test circshift!(a, 10) == 1:5
 end
 
 @testset "circcopy" begin