fix it and remove global check

Author: oxinabox

docs/src/index.md

@@ -9,12 +9,6 @@ For information about ChainRules, including how to write rules, refer to the gen
 [![](https://img.shields.io/badge/docs-main-blue.svg)](https://JuliaDiff.github.io/ChainRulesCore.jl/dev)
 [![](https://img.shields.io/badge/docs-stable-blue.svg)](https://JuliaDiff.github.io/ChainRulesCore.jl/stable)
 
-## Testing Method Table Sensibility
-A basic feature of ChainRulesTestUtils is its ability to check that the method tables for `rrule` and `frule` remain sensible.
-This searches the method tables for methods that should not exist and when it fails tells you where they were defined.
-By calling [`test_method_tables`](@ref) ChainRulesTestUtils will check for things such as having attracted a rule to `DataType` rather than attaching it to a constructor.
-Basically all packages using ChainRulesTestUtils can use [`test_method_tables`](@ref), as it is independent of what rules you have written.
-
 ## Canonical example of testing frule and rrule
 
 Let's suppose a custom transformation has been defined

src/ChainRulesTestUtils.jl

@@ -28,10 +28,10 @@ include("iterator.jl")
 
 include("output_control.jl")
 include("check_result.jl")
+include("method_checks.jl")
 
 include("rule_config.jl")
 include("finite_difference_calls.jl")
 include("testers.jl")
 
-include("global_checks.jl")
 end # module

src/global_checks.jl renamed to src/method_checks.jl

@@ -26,7 +26,8 @@ function test_method_signature(::typeof(rrule), method::Method)
         function_type = if method.sig <: Tuple{Any, RuleConfig, Type, Vararg}
             _parameters(method.sig)[3]
         elseif method.sig <: Tuple{Any, Type, Vararg}
-            _parameters(method.sig)else
+            _parameters(method.sig)[2]
+        else
             nothing
         end
 
@@ -53,29 +54,3 @@ function test_method_signature(::typeof(frule), method::Method)
         )
     end
 end
-
-"""
-    test_method_tables()
-
-Checks that the method tables for `rrule` and `frule` are sensible.
-This in future may carry out a number of checks, but presently just checks to make sure that
-no rules have been added to the very general `DataType`, `Union` or `UnionAll` types,
-which is easy to do accidentally when writing rules for constructors.
-It happens if you write e.g. `rrule(::typeof(Foo), x)` rather than `rrule(::Type{<:Foo}, x)`.
-This would then actually define `rrule(::DataType, x)`. (or `UnionAll` if `Foo`
-was parametric, or `Union` if `Foo` was a type alias for a `Union`)
-"""
-function test_method_tables()
-    @testset "Sensible Constructors" 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)
-            test_method_signature(method)
-        end
-        # frule
-        for method in methods(frule)
-            test_method_signature(frule, method)
-        end
-    end
-end

test/global_checks.jl

@@ -0,0 +1,30 @@
+struct BadConstructor
+    x
+end
+
+if VERSION >= v"1.3"
+    # we only test in Julia 1.3 or later so we can delete the bad method
+    @testset "test_method_signature.jl" begin
+        test_method_signature = ChainRulesTestUtils.test_method_signature
+        
+        ChainRulesCore.rrule(::typeof(BadConstructor), x) = nothing
+        m = Base.which(rrule, (DataType, Any))
+        @test fails(()->test_method_signature(rrule, m))       
+        Base.delete_method(m)
+
+        ChainRulesCore.rrule(::RuleConfig, ::typeof(BadConstructor), x) = nothing
+        m = Base.which(rrule, (RuleConfig, DataType, Any))
+        @test fails(()->test_method_signature(rrule, m))       
+        Base.delete_method(m)
+
+        ChainRulesCore.frule(::Any, ::typeof(BadConstructor), x) = nothing
+        m = Base.which(frule, (Any, DataType, Any))
+        @test fails(()->test_method_signature(frule, m))       
+        Base.delete_method(m)
+
+        ChainRulesCore.frule(::RuleConfig, ::Any, ::typeof(BadConstructor), x) = nothing
+        m = Base.which(frule, (RuleConfig, Any, DataType, Any))
+        @test fails(()->test_method_signature(frule, m))       
+        Base.delete_method(m)
+    end
+end

test/method_checks.jl

@@ -17,5 +17,5 @@ ChainRulesTestUtils.TEST_INFERRED[] = true
     include("data_generation.jl")
     include("rand_tangent.jl")
 
-    include("global_checks.jl")
+    include("method_checks.jl")
 end