Fix interface (#98)

src/interface.jl

@@ -10,7 +10,8 @@ function value_and_pullback!!(rule::R, ȳ::T, fx::Vararg{CoDual, N}) where {R,
     out, pb!! = rule(fx...)
     @assert _typeof(tangent(out)) == T
     ty = increment!!(tangent(out), ȳ)
-    return primal(out), pb!!(ty, map(tangent, fx)...)
+    v = copy(primal(out))
+    return v, pb!!(ty, map(tangent, fx)...)
 end
 
 """

test/interface.jl

@@ -1,13 +1,10 @@
 @testset "interface" begin
-    f = (x, y) -> x * y + sin(x) * cos(y)
-    x = 5.0
-    y = 4.0
-    rule = build_rrule(f, x, y)
-    v, grad = value_and_gradient!!(rule, f, x, y)
-    @test v ≈ f(x, y)
-    @test grad isa Tuple{NoTangent, Float64, Float64}
-
-    v, grad2 = value_and_pullback!!(rule, 1.0, f, x, y)
-    @test v ≈ f(x, y)
-    @test grad == grad2
+    @testset "$(typeof((f, x...)))" for (ȳ, f, x...) in Any[
+        (1.0, (x, y) -> x * y + sin(x) * cos(y), 5.0, 4.0),
+        ([1.0, 1.0], x -> [sin(x), sin(2x)], 3.0),
+    ]
+        rule = build_rrule(f, x...)
+        v, grad2 = value_and_pullback!!(rule, ȳ, f, x...)
+        @test v ≈ f(x...)
+    end
 end