Export oneto rather than implement range(stop)

NEWS.md

@@ -41,6 +41,7 @@ Standard library changes
 
 * `count` and `findall` now accept an `AbstractChar` argument to search for a character in a string ([#38675]).
 * `range` now supports `start` as an optional keyword argument ([#38041]).
+* `oneto` is exported and allows access to `Base.OneTo`, an optimized version of `1:n` where `n` is an `Integer` ([#39242]).
 * `islowercase` and `isuppercase` are now compliant with the Unicode lower/uppercase categories ([#38574]).
 * `iseven` and `isodd` functions now support non-`Integer` numeric types ([#38976]).
 * `escape_string` can now receive a collection of characters in the keyword

base/exports.jl

@@ -405,6 +405,7 @@ export
     minmax,
     ndims,
     ones,
+    oneto,
     parent,
     parentindices,
     partialsort,

base/range.jl

@@ -415,6 +415,36 @@ struct OneTo{T<:Integer} <: AbstractUnitRange{T}
 end
 OneTo(stop::T) where {T<:Integer} = OneTo{T}(stop)
 OneTo(r::AbstractRange{T}) where {T<:Integer} = OneTo{T}(r)
+
+"""
+    oneto(n)
+
+Create an `AbstractRange` that behaves like to `1:n`. The returned
+range may be more efficient than using `1:n` since the lower limit
+is guaranteed to be one by the type system. The definition in `Base`
+requires that `n` be an `Integer`.
+
+See also [`Base.OneTo`](@ref).
+
+# Examples
+```jldoctest
+julia> oneto(5)
+Base.OneTo(5)
+
+julia> collect( oneto(6) )
+6-element Array{Int64,1}:
+ 1
+ 2
+ 3
+ 4
+ 5
+ 6
+
+julia> oneto(5.5)
+ERROR: MethodError: no method matching Base.OneTo(::Float64)
+...
+```
+"""
 oneto(r) = OneTo(r)
 
 ## Step ranges parameterized by length

test/ranges.jl

@@ -863,6 +863,7 @@ end
     @test 1:10 != 2:10 != 2:11 != Base.OneTo(11)
     @test Base.OneTo(10) != Base.OneTo(11) != 1:10
     @test Base.OneTo(0) == 5:4
+    @test oneto(5) == 1:5
 end
 # issue #2959
 @test 1.0:1.5 == 1.0:1.0:1.5 == 1.0:1.0
@@ -1271,6 +1272,7 @@ end
         @test isempty(r)
         @test length(r) == 0
         @test size(r) == (0,)
+        @test r === oneto(-5)
     end
     let r = Base.OneTo(3)
         @test !isempty(r)
@@ -1290,6 +1292,7 @@ end
         @test broadcast(+, r, 1) === 2:4
         @test 2*r === 2:2:6
         @test r + r === 2:2:6
+        @test r === oneto(3)
         k = 0
         for i in r
             @test i == (k += 1)
@@ -1317,6 +1320,7 @@ end
     @test Base.OneTo{Int32}(1:2) === Base.OneTo{Int32}(2)
     @test Base.OneTo(Int32(1):Int32(2)) === Base.OneTo{Int32}(2)
     @test Base.OneTo{Int16}(3.0) === Base.OneTo{Int16}(3)
+    @test oneto(9) === Base.OneTo{Int}(9)
     @test_throws InexactError(:Int16, Int16, 3.2) Base.OneTo{Int16}(3.2)
 end