Test for things adding rules to DataType/UnionAll

Author: oxinabox

test/global_state.jl

@@ -0,0 +1,44 @@
+"""
+    parameters(type)
+Extracts the type-parameters of the `type`.
+e.g. `parameters(Foo{A, B, C}) == [A, B, C]`
+"""
+parameters(sig::UnionAll) = parameters(sig.body)
+parameters(sig::DataType) = sig.parameters
+parameters(sig::Union) = Base.uniontypes(sig)
+
+@testset "Make sure methods haven't been added to DataType/UnionAll/Union" begin
+    # if someone wrote e.g. `rrule(::typeof(Foo), x)` rather than `rrule(::Type{<:Foo}, x)`
+    # then that would actually define `rrule(::DataType, x)` which would be bad
+    # This test checks for that and fails if such a method exists.
+    for method in methods(rrule)
+        function_type = if method.sig <: Tuple{typeof(rrule), RuleConfig, Type, Vararg}
+            parameters(method.sig)[3]
+        elseif method.sig <: Tuple{typeof(rrule), Type, Vararg}
+            @show parameters(method.sig)[2]
+        else
+            nothing
+        end
+        
+        if function_type == DataType || function_type == UnionAll || function_type == Union
+            @error "Bad constructor rrule. typeof(T)` not `Type{T}`" method
+            @test false
+        end
+    end
+
+    # frule
+    for method in methods(frule)
+        function_type = if method.sig <: Tuple{typeof(frule), RuleConfig, Any, Type, Vararg}
+            parameters(method.sig)[3]
+        elseif method.sig <: Tuple{typeof(frule), Any, Type, Vararg}
+            @show parameters(method.sig)[2]
+        else
+            nothing
+        end
+        
+        if function_type == DataType || function_type == UnionAll || function_type == Union
+            @error "Bad constructor frule. typeof(T)` not `Type{T}`" method
+            @test false
+        end
+    end
+end

test/runtests.jl

@@ -46,6 +46,8 @@ end
     include("test_helpers.jl")
     println()
 
+    include_test("global_state.jl")
+
     # Each file puts all tests inside one or more @testset blocks
     include_test("rulesets/Base/base.jl")
     include_test("rulesets/Base/fastmath_able.jl")