sort! rule tests

test/internal_rules.jl

@@ -0,0 +1,29 @@
+module InternalRules
+
+using Enzyme
+using Enzyme.EnzymeRules
+using Test
+
+@testset "Internal rules" begin
+    function f1(x)
+        a = [1.0, 3.0, x]
+        sort!(a)
+        return a[2]
+    end
+
+    @test autodiff(Forward, f1, Duplicated(2.0, 1.0))[1]   == 1
+    @test autodiff(Reverse, f1, Active, Active(2.0))[1][1] == 1
+    @test autodiff(Forward, f1, Duplicated(4.0, 1.0))[1]   == 0
+    @test autodiff(Reverse, f1, Active, Active(4.0))[1][1] == 0
+
+    function f2(x)
+        a = [1.0, -3.0, -x, -2x, x]
+        sort!(a; rev=true, lt=(x, y) -> abs(x) < abs(y) || (abs(x) == abs(y) && x < y))
+        return sum(a .* [1, 2, 3, 4, 5])
+    end
+
+    @test autodiff(Forward, f2, Duplicated(2.0, 1.0))[1]   == -3
+    @test autodiff(Reverse, f2, Active, Active(2.0))[1][1] == -3
+end
+
+end # InternalRules

test/runtests.jl

@@ -72,6 +72,7 @@ include("typetree.jl")
     include("rrules.jl")
     include("kwrules.jl")
     include("kwrrules.jl")
+    include("internal_rules.jl")
     @static if VERSION ≥ v"1.9-"
         # XXX invalidation does not work on Julia 1.8
         include("ruleinvalidation.jl")