Fix conversion in getindex (JuliaLang#26615)

* Test more out of bounds errors for the UnitRange type

* Do the conversion in getindex of UnitRange only when returning

base/range.jl

@@ -478,11 +478,23 @@ end
 
 ## indexing
 
+_in_unit_range(v::UnitRange, val, i::Integer) = i > 0 && val <= v.stop && val >= v.start
+
 function getindex(v::UnitRange{T}, i::Integer) where T
  @_inline_meta
- ret = convert(T, first(v) + i - 1)
- @boundscheck ((i > 0) & (ret <= v.stop) & (ret >= v.start)) || throw_boundserror(v, i)
- ret
+ val = convert(T, v.start + i - 1)
+ @boundscheck _in_unit_range(v, val, i) || throw_boundserror(v, i)
+ val
+end
+
+const OverflowSafe = Union{Bool,Int8,Int16,Int32,Int64,Int128,
+ UInt8,UInt16,UInt32,UInt64,UInt128}
+
+function getindex(v::UnitRange{T}, i::Integer) where {T<:OverflowSafe}
+ @_inline_meta
+ val = v.start + i - 1
+ @boundscheck _in_unit_range(v, val, i) || throw_boundserror(v, i)
+ val % T
 end
 
 function getindex(v::OneTo{T}, i::Integer) where T

test/ranges.jl

@@ -1286,6 +1286,12 @@ end
  @test x isa StepRangeLen{Float64,Base.TwicePrecision{Float64},Base.TwicePrecision{Float64}}
 end
 
+@testset "Issue #26608" begin
+ @test_throws BoundsError (Int8(-100):Int8(100))[400]
+ @test_throws BoundsError (-100:100)[typemax(UInt)]
+ @test_throws BoundsError (false:true)[3]
+end
+
 module NonStandardIntegerRangeTest
 
 using Test