Allow showing of StepRangLen{T} with generic T (#49516)

(cherry picked from commit ee95843)

Author: SamuelBadr

base/range.jl

@@ -1093,7 +1093,7 @@ show(io::IO, r::AbstractRange) = print(io, repr(first(r)), ':', repr(step(r)), '
 show(io::IO, r::UnitRange) = print(io, repr(first(r)), ':', repr(last(r)))
 show(io::IO, r::OneTo) = print(io, "Base.OneTo(", r.stop, ")")
 function show(io::IO, r::StepRangeLen)
-    if step(r) != 0
+    if !iszero(step(r))
         print(io, repr(first(r)), ':', repr(step(r)), ':', repr(last(r)))
     else
         # ugly temporary printing, to avoid 0:0:0 etc.

test/ranges.jl

@@ -2392,3 +2392,16 @@ end
     @test test_firstindex(StepRange{Union{Int64,Int128},Int}(Int64(1), 1, Int128(1)))
     @test test_firstindex(StepRange{Union{Int64,Int128},Int}(Int64(1), 1, Int128(0)))
 end
+
+@testset "PR 49516" begin
+	struct PR49516 <: Signed
+		n::Int
+	end
+	PR49516(f::PR49516) = f
+	Base.:*(x::Integer, f::PR49516) = PR49516(*(x, f.n))
+	Base.:+(f1::PR49516, f2::PR49516) = PR49516(+(f1.n, f2.n))
+	Base.show(io::IO, f::PR49516) = print(io, "PR49516(", f.n, ")")
+
+	srl = StepRangeLen(PR49516(1), PR49516(2), 10)
+	@test sprint(show, srl) == "PR49516(1):PR49516(2):PR49516(19)"
+end