zero-index get/setindex(::ReinterpretArray) require a length of 1

NEWS.md

@@ -17,6 +17,8 @@ is considered a bug fix ([#47102])
 
   - The `hash` algorithm and its values have changed. Most `hash` specializations will remain correct and require no action. Types that reimplement the core hashing logic independently, such as some third-party string packages do, may require a migration to the new algorithm. ([#57509])
 
+* Indexless `getindex` and `setindex!` (i.e. `A[]`) on `ReinterpretArray` now correctly throw a `BoundsError` when there is more than one element. ([#58814])
+
 Compiler/Runtime improvements
 -----------------------------
 

base/reinterpretarray.jl

@@ -391,7 +391,7 @@ check_ptr_indexable(a::Array, sz) = sizeof(eltype(a)) !== sz
 check_ptr_indexable(a::Memory, sz) = true
 check_ptr_indexable(a::AbstractArray, sz) = false
 
-@propagate_inbounds getindex(a::ReinterpretArray) = a[firstindex(a)]
+@propagate_inbounds getindex(a::ReshapedReinterpretArray{T,0}) where {T} = a[firstindex(a)]
 
 @propagate_inbounds isassigned(a::ReinterpretArray, inds::Integer...) = checkbounds(Bool, a, inds...) && (check_ptr_indexable(a) || _isassigned_ra(a, inds...))
 @propagate_inbounds isassigned(a::ReinterpretArray, inds::SCartesianIndex2) = isassigned(a.parent, inds.j)
@@ -541,7 +541,7 @@ end
     setindex!(a, v, firstindex(a))
 end
 
-@propagate_inbounds setindex!(a::ReinterpretArray, v) = setindex!(a, v, firstindex(a))
+@propagate_inbounds setindex!(a::ReshapedReinterpretArray{T,0}, v) where {T} = setindex!(a, v, firstindex(a))
 
 @propagate_inbounds function setindex!(a::ReinterpretArray{T,N,S}, v, inds::Vararg{Int, N}) where {T,N,S}
     check_writable(a)

test/reinterpretarray.jl

@@ -21,6 +21,7 @@ A = Int64[1, 2, 3, 4]
 Ars = Int64[1 3; 2 4]
 B = Complex{Int64}[5+6im, 7+8im, 9+10im]
 Av = [Int32[1,2], Int32[3,4]]
+C = view([1,1], [1,2])
 
 test_many_wrappers(Ars, (identity, tslow)) do Ar
     @test @inferred(ndims(reinterpret(reshape, Complex{Int64}, Ar))) == 1
@@ -36,6 +37,10 @@ test_many_wrappers(B, (identity, tslow)) do _B
     @test @inferred(size(reinterpret(reshape, Int128, _B))) == (3,)
 end
 
+test_many_wrappers(C) do Cr
+    @test reinterpret(reshape, Tuple{Int8, Int}, Cr) == fill((1,1))
+end
+
 @test_throws ArgumentError("cannot reinterpret `Int64` as `Vector{Int64}`, type `Vector{Int64}` is not a bits type") reinterpret(Vector{Int64}, A)
 @test_throws ArgumentError("cannot reinterpret `Vector{Int32}` as `Int32`, type `Vector{Int32}` is not a bits type") reinterpret(Int32, Av)
 @test_throws ArgumentError("cannot reinterpret a zero-dimensional `Int64` array to `Int32` which is of a different size") reinterpret(Int32, reshape([Int64(0)]))
@@ -272,7 +277,7 @@ test_many_wrappers(fill(1.0, 5, 3), (identity, wrapper)) do a_
     fill!(r, 2)
     @test all(a .=== reinterpret(Float64, [Int64(2)])[1])
     @test all(r .=== Int64(2))
-    for badinds in (0, 16, (0,1), (1,0), (6,3), (5,4))
+    for badinds in ((), 0, 16, (0,1), (1,0), (6,3), (5,4))
         @test_throws BoundsError r[badinds...]
         @test_throws BoundsError r[badinds...] = -2
     end
@@ -285,7 +290,7 @@ test_many_wrappers(fill(1.0, 5, 3), (identity, wrapper)) do a_
     fill!(r, 3)
     @test all(a .=== reinterpret(Float64, [(Int32(3), Int32(3))])[1])
     @test all(r .=== Int32(3))
-    for badinds in (0, 31, (0,1), (1,0), (11,3), (10,4))
+    for badinds in ((), 0, 31, (0,1), (1,0), (11,3), (10,4))
         @test_throws BoundsError r[badinds...]
         @test_throws BoundsError r[badinds...] = -3
     end
@@ -298,7 +303,7 @@ test_many_wrappers(fill(1.0, 5, 3), (identity, wrapper)) do a_
     fill!(r, 4)
     @test all(a[1:2:5,:] .=== reinterpret(Float64, [Int64(4)])[1])
     @test all(r .=== Int64(4))
-    for badinds in (0, 10, (0,1), (1,0), (4,3), (3,4))
+    for badinds in ((), 0, 10, (0,1), (1,0), (4,3), (3,4))
         @test_throws BoundsError r[badinds...]
         @test_throws BoundsError r[badinds...] = -4
     end
@@ -311,7 +316,7 @@ test_many_wrappers(fill(1.0, 5, 3), (identity, wrapper)) do a_
     fill!(r, 5)
     @test all(a[1:2:5,:] .=== reinterpret(Float64, [(Int32(5), Int32(5))])[1])
     @test all(r .=== Int32(5))
-    for badinds in (0, 19, (0,1), (1,0), (7,3), (6,4))
+    for badinds in ((), 0, 19, (0,1), (1,0), (7,3), (6,4))
         @test_throws BoundsError r[badinds...]
         @test_throws BoundsError r[badinds...] = -5
     end