add default constructors for AbstractRange

base/range.jl

@@ -264,6 +264,11 @@ RangeStepStyle(::Type{<:AbstractRange{<:Integer}}) = RangeStepRegular()
 
 convert(::Type{T}, r::AbstractRange) where {T<:AbstractRange} = r isa T ? r : T(r)::T
 
+# there is no complex range
+AbstractRange{T}(r::AbstractRange) where T<:Real = T(first(r)):T(step(r)):T(last(r))
+AbstractArray{T,1}(r::AbstractRange) where T<:Real = AbstractRange{T}(r)
+AbstractArray{T}(r::AbstractRange) where T<:Real = AbstractRange{T}(r)
+
 ## ordinal ranges
 
 """
@@ -287,6 +292,8 @@ Supertype for ranges with a step size of [`oneunit(T)`](@ref) with elements of t
 """
 abstract type AbstractUnitRange{T} <: OrdinalRange{T,T} end
 
+AbstractRange{T}(r::AbstractUnitRange) where {T<:Integer} = AbstractUnitRange{T}(r)
+
 """
     StepRange{T, S} <: OrdinalRange{T, S}
 

test/ranges.jl

@@ -1183,6 +1183,9 @@ end
     @test convert(LinRange, 0.0:0.1:0.3) === LinRange{Float64}(0.0, 0.3, 4)
     @test convert(LinRange, 0:3) === LinRange{Int}(0, 3, 4)
 
+    @test convert(AbstractRange{Int8},0:5) === convert(AbstractVector{Int8},0:5) ===convert(AbstractArray{Int8},0:5) === Int8(0):Int8(5)
+    @test convert(AbstractRange{Float64},0:5) === convert(AbstractVector{Float64},0:5) === convert(AbstractArray{Float64},0:5) === 0.:1.:5.
+
     @test promote('a':'z', 1:2) === ('a':'z', 1:1:2)
     @test eltype(['a':'z', 1:2]) == (StepRange{T,Int} where T)
 end