range: Refactor one positional argument

Author: mkitti

base/range.jl

@@ -136,9 +136,7 @@ A `UnitRange` is not produced if `step` is provided even if specified as one.
 function range end
 
 range(start; stop=nothing, length::Union{Integer,Nothing}=nothing, step=nothing) =
-    stop === length === step === nothing ?
-    _range(nothing, nothing, start, nothing) :
-    _range(start, step, stop, length)
+    _range_positional(start, step, stop, length)
 
 function range(start, stop; length::Union{Integer,Nothing}=nothing, step=nothing)
     # For code clarity, the user must pass step or length
@@ -158,10 +156,15 @@ end
 range(;start=nothing, stop=nothing, length::Union{Integer, Nothing}=nothing, step=nothing) =
     _range(start, step, stop, length)
 
-range(length::Integer) = OneTo(length)
+range(stop::Integer) = range_stop(stop)
+
+_range_positional(stop::Any    , step::Nothing,      ::Nothing, len::Nothing) =
+    _range(nothing, nothing, stop, nothing) # One arg interpreted as `stop`, could be nothing
+_range_positional(start::Any    , step::Any    , stop::Any,     len::Any) =
+    _range(start, step, stop, len)
 
 _range(start::Nothing, step::Nothing, stop::Nothing, len::Nothing) = range_error(start, step, stop, len)
-_range(start::Nothing, step::Nothing, stop::Nothing, len::Any    ) = OneTo(len)
+_range(start::Nothing, step::Nothing, stop::Nothing, len::Any    ) = range_length(len)
 _range(start::Nothing, step::Nothing, stop::Any    , len::Nothing) = range_stop(stop)
 _range(start::Nothing, step::Nothing, stop::Any    , len::Any    ) = range_stop_length(stop, len)
 _range(start::Nothing, step::Any    , stop::Nothing, len::Nothing) = range_error(start, step, stop, len)
@@ -177,6 +180,8 @@ _range(start::Any    , step::Any    , stop::Nothing, len::Any    ) = range_start
 _range(start::Any    , step::Any    , stop::Any    , len::Nothing) = range_start_step_stop(start, step, stop)
 _range(start::Any    , step::Any    , stop::Any    , len::Any    ) = range_error(start, step, stop, len)
 
+range_length(len::Integer) = OneTo(len)
+
 range_stop(stop) = oneunit(stop):stop
 range_stop(stop::Integer) = OneTo(stop)