Fix reverse of ranges of unsigned integers

Fixes #29576

Co-authored-by: Jameson Nash <vtjnash@gmail.com>

base/broadcast.jl

@@ -9,7 +9,7 @@ module Broadcast
 
 using .Base.Cartesian
 using .Base: Indices, OneTo, tail, to_shape, isoperator, promote_typejoin, promote_typejoin_union, @pure,
-             _msk_end, unsafe_bitgetindex, bitcache_chunks, bitcache_size, dumpbitcache, unalias
+             _msk_end, unsafe_bitgetindex, bitcache_chunks, bitcache_size, dumpbitcache, unalias, negate
 import .Base: copy, copyto!, axes
 export broadcast, broadcast!, BroadcastStyle, broadcast_axes, broadcastable, dotview, @__dot__, BroadcastFunction
 
@@ -1079,9 +1079,9 @@ end
 # DefaultArrayStyle and \ are not available at the time of range.jl
 broadcasted(::DefaultArrayStyle{1}, ::typeof(+), r::AbstractRange) = r
 
-broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::AbstractRange) = range(-first(r), step=-step(r), length=length(r))
-broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::OrdinalRange) = range(-first(r), -last(r), step=-step(r))
-broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::StepRangeLen) = StepRangeLen(-r.ref, -r.step, length(r), r.offset)
+broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::AbstractRange) = range(-first(r), step=negate(step(r)), length=length(r))
+broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::OrdinalRange) = range(-first(r), -last(r), step=negate(step(r)))
+broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::StepRangeLen) = StepRangeLen(-r.ref, negate(r.step), length(r), r.offset)
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::LinRange) = LinRange(-r.start, -r.stop, length(r))
 
 # For #18336 we need to prevent promotion of the step type:
@@ -1102,15 +1102,15 @@ broadcasted(::DefaultArrayStyle{1}, ::typeof(+), x::Number, r::LinRange) = LinRa
 broadcasted(::DefaultArrayStyle{1}, ::typeof(+), r1::AbstractRange, r2::AbstractRange) = r1 + r2
 
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::AbstractRange, x::Number) = range(first(r) - x, step=step(r), length=length(r))
-broadcasted(::DefaultArrayStyle{1}, ::typeof(-), x::Number, r::AbstractRange) = range(x - first(r), step=-step(r), length=length(r))
+broadcasted(::DefaultArrayStyle{1}, ::typeof(-), x::Number, r::AbstractRange) = range(x - first(r), step=negate(step(r)), length=length(r))
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::OrdinalRange, x::Integer) = range(first(r) - x, last(r) - x, step=step(r))
-broadcasted(::DefaultArrayStyle{1}, ::typeof(-), x::Integer, r::OrdinalRange) = range(x - first(r), x - last(r), step=-step(r))
+broadcasted(::DefaultArrayStyle{1}, ::typeof(-), x::Integer, r::OrdinalRange) = range(x - first(r), x - last(r), step=negate(step(r)))
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::AbstractUnitRange, x::Integer) = range(first(r) - x, last(r) - x)
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::AbstractUnitRange, x::Real) = range(first(r) - x, length=length(r))
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::StepRangeLen{T}, x::Number) where T =
     StepRangeLen{typeof(T(r.ref)-x)}(r.ref - x, r.step, length(r), r.offset)
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), x::Number, r::StepRangeLen{T}) where T =
-    StepRangeLen{typeof(x-T(r.ref))}(x - r.ref, -r.step, length(r), r.offset)
+    StepRangeLen{typeof(x-T(r.ref))}(x - r.ref, negate(r.step), length(r), r.offset)
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r::LinRange, x::Number) = LinRange(r.start - x, r.stop - x, length(r))
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), x::Number, r::LinRange) = LinRange(x - r.start, x - r.stop, length(r))
 broadcasted(::DefaultArrayStyle{1}, ::typeof(-), r1::AbstractRange, r2::AbstractRange) = r1 - r2

base/int.jl

@@ -87,6 +87,10 @@ signed(::Type{T}) where {T<:Signed} = T
 (+)(x::T, y::T) where {T<:BitInteger} = add_int(x, y)
 (*)(x::T, y::T) where {T<:BitInteger} = mul_int(x, y)
 
+negate(x) = -x
+negate(x::Unsigned) = -convert(Signed, x)
+#widenegate(x) = -convert(widen(signed(typeof(x))), x)
+
 inv(x::Integer) = float(one(x)) / float(x)
 (/)(x::T, y::T) where {T<:Integer} = float(x) / float(y)
 # skip promotion for system integer types

base/range.jl

@@ -1234,7 +1234,7 @@ issubset(r::AbstractUnitRange{<:Integer}, s::AbstractUnitRange{<:Integer}) =
 
 ## linear operations on ranges ##
 
--(r::OrdinalRange) = range(-first(r), step=-step(r), length=length(r))
+-(r::OrdinalRange) = range(-first(r), step=negate(step(r)), length=length(r))
 -(r::StepRangeLen{T,R,S,L}) where {T,R,S,L} =
     StepRangeLen{T,R,S,L}(-r.ref, -r.step, r.len, r.offset)
 function -(r::LinRange)
@@ -1340,13 +1340,13 @@ end
 Array{T,1}(r::AbstractRange{T}) where {T} = vcat(r)
 collect(r::AbstractRange) = vcat(r)
 
-_reverse(r::OrdinalRange, ::Colon) = (:)(last(r), -step(r), first(r))
+_reverse(r::OrdinalRange, ::Colon) = (:)(last(r), negate(step(r)), first(r))
 function _reverse(r::StepRangeLen, ::Colon)
     # If `r` is empty, `length(r) - r.offset + 1 will be nonpositive hence
     # invalid. As `reverse(r)` is also empty, any offset would work so we keep
     # `r.offset`
     offset = isempty(r) ? r.offset : length(r)-r.offset+1
-    return typeof(r)(r.ref, -r.step, length(r), offset)
+    return typeof(r)(r.ref, negate(r.step), length(r), offset)
 end
 _reverse(r::LinRange{T}, ::Colon) where {T} = typeof(r)(r.stop, r.start, length(r))
 

test/ranges.jl

@@ -367,6 +367,14 @@ end
         @test reverse(reverse(typemin(Int):typemax(Int))) == typemin(Int):typemax(Int)
         @test reverse(reverse(typemin(Int):2:typemax(Int))) == typemin(Int):2:typemax(Int)
     end
+    @testset "reverse `[Step|Unit]Range{$T}`" for T in (Int8, UInt8, Int, UInt, Int128, UInt128)
+        @test reverse(T(1):T(10)) == T(10):-1:T(1)
+        @test reverse(typemin(T):typemax(T)) == typemax(T):-1:typemin(T)
+        @test reverse(typemin(T):2:typemax(T)) == typemax(T)-T(1):-2:typemin(T)
+        @test reverse(reverse(T(1):T(10))) == T(1):T(10)
+        @test reverse(reverse(typemin(T):typemax(T))) == typemin(T):typemax(T)
+        @test reverse(reverse(typemin(T):2:typemax(T))) == typemin(T):2:typemax(T)
+    end
     @testset "intersect" begin
         @test intersect(1:5, 2:3) == 2:3
         @test intersect(-3:5, 2:8) == 2:5
@@ -699,9 +707,9 @@ end
     @test broadcast(-, T(1):2:6, 1) === T(0):2:4
     @test broadcast(-, T(1):2:6, 0.3) === range(T(1)-0.3, step=2, length=T(3)) == T(1)-0.3:2:5-0.3
     is_unsigned = T <: Unsigned
-    is_unsigned && @test length(broadcast(-, T(1):3, 2)) === length(T(1)-2:T(3)-2)
-    @test broadcast(-, T(1):3) == -T(1):-T(1):-T(3)
-    @test broadcast(-, 2, T(1):3) == T(1):-T(1):-T(1)
+    @test length(broadcast(-, T(1):3, 2)) === length(T(1)-2:T(3)-2) === (is_unsigned ? T(0) : T(3))
+    @test broadcast(-, T(1):3) == -T(1):-1:-T(3)
+    @test broadcast(-, 2, T(1):3) == T(1):-1:-T(1)
 end
 @testset "operations between ranges and arrays" for T in (Int, UInt, Int128)
     @test all(([T(1):5;] + (T(5):-1:1)) .=== T(6))