Make ranges more robust with unsigned indexes. (#50823)

Fixes #44895

Author: gbaraldi

base/range.jl

@@ -963,13 +963,13 @@ end
 # This is separate to make it useful even when running with --check-bounds=yes
 function unsafe_getindex(r::StepRangeLen{T}, i::Integer) where T
     i isa Bool && throw(ArgumentError("invalid index: $i of type Bool"))
-    u = i - r.offset
+    u = oftype(r.offset, i) - r.offset
     T(r.ref + u*r.step)
 end
 
 function _getindex_hiprec(r::StepRangeLen, i::Integer)  # without rounding by T
     i isa Bool && throw(ArgumentError("invalid index: $i of type Bool"))
-    u = i - r.offset
+    u = oftype(r.offset, i) - r.offset
     r.ref + u*r.step
 end
 

base/twiceprecision.jl

@@ -478,15 +478,15 @@ function unsafe_getindex(r::StepRangeLen{T,<:TwicePrecision,<:TwicePrecision}, i
     # Very similar to _getindex_hiprec, but optimized to avoid a 2nd call to add12
     @inline
     i isa Bool && throw(ArgumentError("invalid index: $i of type Bool"))
-    u = i - r.offset
+    u = oftype(r.offset, i) - r.offset
     shift_hi, shift_lo = u*r.step.hi, u*r.step.lo
     x_hi, x_lo = add12(r.ref.hi, shift_hi)
     T(x_hi + (x_lo + (shift_lo + r.ref.lo)))
 end
 
 function _getindex_hiprec(r::StepRangeLen{<:Any,<:TwicePrecision,<:TwicePrecision}, i::Integer)
     i isa Bool && throw(ArgumentError("invalid index: $i of type Bool"))
-    u = i - r.offset
+    u = oftype(r.offset, i) - r.offset
     shift_hi, shift_lo = u*r.step.hi, u*r.step.lo
     x_hi, x_lo = add12(r.ref.hi, shift_hi)
     x_hi, x_lo = add12(x_hi, x_lo + (shift_lo + r.ref.lo))

test/ranges.jl

@@ -2528,3 +2528,10 @@ end
     end
 
 end
+
+@testset "unsigned index #44895" begin
+    x = range(-1,1,length=11)
+    @test x[UInt(1)] == -1.0
+    a = StepRangeLen(1,2,3,2)
+    @test a[UInt(1)] == -1
+end

test/testhelpers/OffsetArrays.jl

@@ -142,7 +142,7 @@ end
 @inline function Base.getindex(r::IdOffsetRange, i::Integer)
     i isa Bool && throw(ArgumentError("invalid index: $i of type Bool"))
     @boundscheck checkbounds(r, i)
-    @inbounds eltype(r)(r.parent[i - r.offset] + r.offset)
+    @inbounds eltype(r)(r.parent[oftype(r.offset, i) - r.offset] + r.offset)
 end
 
 # Logical indexing following https://github.com/JuliaLang/julia/pull/31829
@@ -592,7 +592,7 @@ Base.fill!(A::OffsetArray, x) = parent_call(Ap -> fill!(Ap, x), A)
 #   Δi = i - first(r)
 #   i′ = first(r.parent) + Δi
 # and one obtains the result below.
-parentindex(r::IdOffsetRange, i) = i - r.offset
+parentindex(r::IdOffsetRange, i) = oftype(r.offset, i) - r.offset
 
 @propagate_inbounds Base.getindex(A::OffsetArray{<:Any,0})  = A.parent[]