fix #33882, step(::StepRangeLen) should not usually convert (#34412)

Author: JeffBezanson

base/range.jl

@@ -500,7 +500,8 @@ julia> step(range(2.5, stop=10.9, length=85))
 """
 step(r::StepRange) = r.step
 step(r::AbstractUnitRange{T}) where{T} = oneunit(T) - zero(T)
-step(r::StepRangeLen{T}) where {T} = T(r.step)
+step(r::StepRangeLen) = r.step
+step(r::StepRangeLen{T}) where {T<:AbstractFloat} = T(r.step)
 step(r::LinRange) = (last(r)-first(r))/r.lendiv
 
 step_hp(r::StepRangeLen) = r.step

test/ranges.jl

@@ -1560,3 +1560,9 @@ end
     @test_throws MethodError mod(3, 1:2:7)
     @test_throws DivideError mod(3, 1:0)
 end
+
+@testset "issue #33882" begin
+    r = StepRangeLen('a',2,4)
+    @test step(r) === 2
+    @test collect(r) == ['a','c','e','g']
+end