Fix 29545: Implement unaliascopy for ReinterpretArray (#30296)

* Fix 29545: Implement unaliascopy for ReinterpretArray

(cherry picked from commit f611b46)

Author: mbauman

base/reinterpretarray.jl

@@ -68,6 +68,7 @@ IndexStyle(a::ReinterpretArray) = IndexStyle(a.parent)
 
 parent(a::ReinterpretArray) = a.parent
 dataids(a::ReinterpretArray) = dataids(a.parent)
+unaliascopy(a::ReinterpretArray{T}) where {T} = reinterpret(T, unaliascopy(a.parent))
 
 function size(a::ReinterpretArray{T,N,S} where {N}) where {T,S}
     psize = size(a.parent)

test/reinterpretarray.jl

@@ -161,6 +161,16 @@ let a = [0.1 0.2; 0.3 0.4], at = reshape([(i,i+1) for i = 1:2:8], 2, 2)
     @test r == OffsetArray(reshape(1:8, 2, 2, 2), (0, offsetvt...))
 end
 
+@testset "potentially aliased copies" begin
+    buffer = UInt8[1,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0]
+    mid = length(buffer) ÷ 2
+    x1 = reinterpret(Int64, @view buffer[1:mid])
+    x2 = reinterpret(Int64, @view buffer[mid+1:end])
+    x1 .= x2
+    @test x1 == x2 == [2]
+    @test x1[] === x2[] === Int64(2)
+end
+
 # Test 0-dimensional Arrays
 A = zeros(UInt32)
 B = reinterpret(Int32,A)