Resolve test_approx ambiguities (#253)

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRulesTestUtils"
 uuid = "cdddcdb0-9152-4a09-a978-84456f9df70a"
-version = "1.9.0"
+version = "1.9.1"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/check_result.jl

@@ -24,7 +24,16 @@ function test_approx(
     @test_msg msg isapprox(actual, expected; kwargs...)
 end
 
-for (T1, T2) in ((AbstractThunk, Any), (AbstractThunk, AbstractThunk), (Any, AbstractThunk))
+for (T1, T2) in
+    (
+        (AbstractThunk, Any),
+        (AbstractThunk, AbstractThunk),
+        (Any, AbstractThunk),
+        (Tangent, AbstractThunk),
+        (AbstractThunk, Tangent),
+        (AbstractZero, AbstractThunk),
+        (AbstractThunk, AbstractZero),
+    )
     @eval function test_approx(actual::$T1, expected::$T2, msg=""; kwargs...)
         return test_approx(unthunk(actual), unthunk(expected), msg; kwargs...)
     end
@@ -123,9 +132,8 @@ function test_approx(actual::Tangent{P,T}, expected, msg=""; kwargs...) where {T
 end
 test_approx(x, y::Tangent, msg=""; kwargs...) = test_approx(y, x, msg; kwargs...)
 
-function test_approx(actual::Tangent, expected::AbstractThunk, msg=""; kwargs...)
-    return test_approx(actual, unthunk(expected), msg; kwargs...)
-end
+test_approx(z::NoTangent, t::Tangent, msg=""; kwargs...) = all(==(NoTangent()), t)
+test_approx(t::Tangent, z::NoTangent, msg=""; kwargs...) = all(==(NoTangent()), t)
 
 # This catches comparisons of Tangents and Tuples/NamedTuple
 # and gives an error message complaining about that. the `@test` will definitely fail

test/check_result.jl

@@ -83,6 +83,20 @@ end
                 Tangent{Tuple{Float64,Float64}}(1.0, 2.0),
                 @thunk(Tangent{Tuple{Float64,Float64}}(1.0, 2.0)),
             )
+            test_approx(
+                @thunk(Tangent{Tuple{Float64,Float64}}(1.0, 2.0)),
+                Tangent{Tuple{Float64,Float64}}(1.0, 2.0),
+            )
+            test_approx(@thunk(ZeroTangent()), ZeroTangent())
+            test_approx(ZeroTangent(), @thunk(ZeroTangent()))
+            test_approx(
+                Tangent{Tuple{Float64,Float64}}(NoTangent(), NoTangent()),
+                NoTangent(),
+            )
+            test_approx(
+                NoTangent(),
+                Tangent{Tuple{Float64,Float64}}(NoTangent(), NoTangent()),
+            )
         end
         @testset "negative case" begin
             @test fails(() -> test_approx(1.0, 2.0))