From a8cd1f7fd7f40a79a7da58e864ba9aff12a28173 Mon Sep 17 00:00:00 2001
From: Gabriel Baraldi <baraldigabriel@gmail.com>
Date: Mon, 7 Aug 2023 16:52:17 -0300
Subject: [PATCH] Make ranges more robust with unsigned indexes.

---
 base/range.jl          | 18 ++++++++++++++----
 base/twiceprecision.jl | 12 ++++++++++--
 test/ranges.jl         |  5 +++++
 3 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/base/range.jl b/base/range.jl
index e8ffe10e2ba7f..ac4bbf28e2de1 100644
--- a/base/range.jl
+++ b/base/range.jl
@@ -963,14 +963,24 @@ 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
-    T(r.ref + u*r.step)
+    if i < r.offset # 1 <= offset <= len && 1 <= i <= len
+        u = r.offset - i
+        return T(r.ref - u*r.step)
+    else
+        u = i - r.offset
+        return T(r.ref + u*r.step)
+    end
 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
-    r.ref + u*r.step
+    if i < r.offset # 1 <= offset <= len && 1 <= i <= len
+        u = r.offset - i
+        return r.ref - u*r.step
+    else
+        u = i - r.offset
+        return r.ref + u*r.step
+    end
 end
 
 function unsafe_getindex(r::LinRange, i::Integer)
diff --git a/base/twiceprecision.jl b/base/twiceprecision.jl
index d91a04371230c..24b10afb033af 100644
--- a/base/twiceprecision.jl
+++ b/base/twiceprecision.jl
@@ -478,7 +478,11 @@ 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
+    if i < r.offset # 1 <= offset <= len && 1 <= i <= len
+        u = r.offset - i
+    else
+        u = i - r.offset
+    end
     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)))
@@ -486,7 +490,11 @@ 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
+    if i < r.offset # 1 <= offset <= len && 1 <= i <= len
+        u = r.offset - i
+    else
+        u = i - r.offset
+    end
     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))
diff --git a/test/ranges.jl b/test/ranges.jl
index 137f9c885da26..05a09fa5c8730 100644
--- a/test/ranges.jl
+++ b/test/ranges.jl
@@ -2528,3 +2528,8 @@ end
     end
 
 end
+
+@testset "unsigned index #44895" begin
+    x = range(-1,1,length=11)
+    x[UInt(1)] == 1.0
+end
\ No newline at end of file