Make var(Range) type stable

Fixes #22773

base/statistics.jl

@@ -210,22 +210,24 @@ varm(iterable, m::Number; corrected::Bool=true) =
 ## variances over ranges
 
 function varm(v::Range, m::Number)
- f = first(v) - m
- s = step(v)
- l = length(v)
+ f = first(v) - m
+ s = step(v)
+ l = length(v)
+ vv = f^2 * l / (l - 1) + f * s * l + s^2 * l * (2 * l - 1) / 6
  if l == 0 || l == 1
-  return NaN
+ return typeof(vv)(NaN)
  end
- return f^2 * l / (l - 1) + f * s * l + s^2 * l * (2 * l - 1) / 6
+ return vv
 end
 
 function var(v::Range)
- s = step(v)
- l = length(v)
+ s = step(v)
+ l = length(v)
+ vv = abs2(s) * (l + 1) * l / 12
  if l == 0 || l == 1
- return NaN
+ return typeof(vv)(NaN)
  end
- return abs2(s) * (l + 1) * l / 12
+ return vv
 end
 
 

test/statistics.jl

@@ -113,6 +113,18 @@ X = [2 3 1 -1; 7 4 5 -4]
 @test isnan(var(1:1))
 @test isnan(var(1:-1))
 
+@test @inferred(var(1.0:8.0)) == 6.
+@test varm(1.0:8.0,1.0) == varm(collect(1.0:8.0),1)
+@test isnan(varm(1.0:1.0,1.0))
+@test isnan(var(1.0:1.0))
+@test isnan(var(1.0:-1.0))
+
+@test @inferred(var(1.0f0:8.0f0)) == 6.f0
+@test varm(1.0f0:8.0f0,1.0f0) == varm(collect(1.0f0:8.0f0),1)
+@test isnan(varm(1.0f0:1.0f0,1.0f0))
+@test isnan(var(1.0f0:1.0f0))
+@test isnan(var(1.0f0:-1.0f0))
+
 @test varm([1,2,3], 2) ≈ 1.
 @test var([1,2,3]) ≈ 1.
 @test var([1,2,3]; corrected=false) ≈ 2.0/3