range uses TwicePrecision when possible (part 2) (#44528)

(cherry picked from commit 45ab664)

Author: jipolanco

base/twiceprecision.jl

@@ -453,8 +453,14 @@ end
 step(r::StepRangeLen{T,TwicePrecision{T},TwicePrecision{T}}) where {T<:AbstractFloat} = T(r.step)
 step(r::StepRangeLen{T,TwicePrecision{T},TwicePrecision{T}}) where {T} = T(r.step)
 
-range_start_step_length(a, st::IEEEFloat, len::Integer) =
-    range_start_step_length(oftype(st, a), st, len)
+range_start_step_length(a::Real, st::IEEEFloat, len::Integer) =
+    range_start_step_length(promote(a, st)..., len)
+
+range_start_step_length(a::IEEEFloat, st::Real, len::Integer) =
+    range_start_step_length(promote(a, st)..., len)
+
+range_start_step_length(a::IEEEFloat, st::IEEEFloat, len::Integer) =
+    range_start_step_length(promote(a, st)..., len)
 
 function range_start_step_length(a::T, st::T, len::Integer) where T<:IEEEFloat
     len = len + 0 # promote with Int
@@ -474,7 +480,13 @@ function range_start_step_length(a::T, st::T, len::Integer) where T<:IEEEFloat
     steprangelen_hp(T, a, st, 0, len, 1)
 end
 
-function range_step_stop_length(step::IEEEFloat, stop, len::Integer)
+range_step_stop_length(step::Real, stop::IEEEFloat, len::Integer) =
+    range_step_stop_length(promote(step, stop)..., len)
+
+range_step_stop_length(step::IEEEFloat, stop::Real, len::Integer) =
+    range_step_stop_length(promote(step, stop)..., len)
+
+function range_step_stop_length(step::IEEEFloat, stop::IEEEFloat, len::Integer)
     r = range_start_step_length(stop, negate(step), len)
     reverse(r)
 end

test/ranges.jl

@@ -1618,9 +1618,51 @@ end
         @test x == [0.0, 0.2, 0.4, 0.6, 0.8]
     end
 
-    let x = @inferred range(stop=1, step=0.2, length=5)
+    let x = @inferred range(0.0, step=2, length=5)
         @test x isa StepRangeLen{Float64,Base.TwicePrecision{Float64},Base.TwicePrecision{Float64}}
-        @test x == [0.2, 0.4, 0.6, 0.8, 1.0]
+        @test x == [0.0, 2.0, 4.0, 6.0, 8.0]
+        @test x === range(0.0, step=2.0, length=5)
+        @test x === range(0.0f0, step=2e0, length=5)
+        @test x === range(0e0, step=2.0f0, length=5)
+    end
+
+    # start::IEEEFloat and step::Complex
+    let x = @inferred range(2.0, step=1im, length=3)
+        @test typeof(x) === StepRangeLen{ComplexF64, Float64, Complex{Int}, Int}
+        @test x == range(2, step=1im, length=3)  # compare with integer range
+        @test x == 2.0 .+ [0im, 1im, 2im]
+    end
+
+    # start::Complex and step::IEEEFloat
+    let x = @inferred range(2im, step=1.0, length=3)
+        @test typeof(x) === StepRangeLen{ComplexF64, Complex{Int}, Float64, Int}
+        @test x == range(2im, step=1, length=3)  # compare with integer range
+    end
+
+    # stop::IEEEFloat and step::Complex
+    let x = @inferred range(stop=2.0, step=1im, length=3)
+        @test typeof(x) === StepRangeLen{ComplexF64, ComplexF64, Complex{Int}, Int}
+        @test x == range(stop=2, step=1im, length=3)  # compare with integer range
+        @test x == 2.0 .- [2im, 1im, 0im]
+    end
+
+    # stop::Complex and step::IEEEFloat
+    let x = @inferred range(stop=2im, step=1.0, length=3)
+        @test typeof(x) === StepRangeLen{ComplexF64, ComplexF64, Float64, Int}
+        @test x == range(stop=2im, step=1, length=3)  # compare with integer range
+    end
+
+    let x = @inferred range(stop=10, step=2.0, length=5)
+        @test x isa StepRangeLen{Float64,Base.TwicePrecision{Float64},Base.TwicePrecision{Float64}}
+        @test x === @inferred range(stop=10.0, step=2.0, length=5)
+        @test x === @inferred range(stop=10f0, step=2.0, length=5)
+        @test x === @inferred range(stop=10e0, step=2.0f0, length=5)
+        @test x == [2, 4, 6, 8, 10]
+    end
+
+    let x = @inferred range(stop=10.0, step=2, length=4)
+        @test x isa StepRangeLen{Float64,Base.TwicePrecision{Float64},Base.TwicePrecision{Float64}}
+        @test x == [4.0, 6.0, 8.0, 10.0]
     end
 end