Support StepRange{T,U} where U is non-numeric (#32671)

With thanks to @quinnj

Author: cmcaine

base/range.jl

@@ -777,9 +777,9 @@ end
 function intersect(r::StepRange, s::StepRange)
     if isempty(r) || isempty(s)
         return range(first(r), step=step(r), length=0)
-    elseif step(s) < 0
+    elseif step(s) < zero(step(s))
         return intersect(r, reverse(s))
-    elseif step(r) < 0
+    elseif step(r) < zero(step(r))
         return reverse(intersect(reverse(r), s))
     end
 
@@ -804,7 +804,7 @@ function intersect(r::StepRange, s::StepRange)
 
     g, x, y = gcdx(step1, step2)
 
-    if rem(start1 - start2, g) != 0
+    if !iszero(rem(start1 - start2, g))
         # Unaligned, no overlap possible.
         return range(start1, step=a, length=0)
     end

test/ranges.jl

@@ -361,6 +361,16 @@ end
 
         @test intersect(1:3, 2) === intersect(2, 1:3) === 2:2
         @test intersect(1.0:3.0, 2) == intersect(2, 1.0:3.0) == [2.0]
+
+        @testset "Support StepRange with a non-numeric step" begin
+            start = Date(1914, 7, 28)
+            stop = Date(1918, 11, 11)
+
+            @test intersect(start:Day(1):stop, start:Day(1):stop) == start:Day(1):stop
+            @test intersect(start:Day(1):stop, start:Day(5):stop) == start:Day(5):stop
+            @test intersect(start-Day(10):Day(1):stop-Day(10), start:Day(5):stop) ==
+                start:Day(5):stop-Day(10)-mod(stop-start, Day(5))
+        end
     end
     @testset "issubset" begin
         @test issubset(1:3, 1:typemax(Int)) #32461