Method ambiguities causing test failures in Julia 1.10+

[christiangnrd]

I was investigating the BitVector sum test errors on CI and it seems to be related to the method ambiguity test failure.

Upon further inspection, it seems like JuliaLang/julia#49349 is the PR that introduced this error.

test_rrule failure output:

julia> test_rrule(sum, randn(5) .> 0; fkwargs=(;dims=dims))
test_rrule: sum on BitVector: Error During Test at /Users/christian/.julia/packages/ChainRulesTestUtils/by7Dj/src/testers.jl:202
  Got exception outside of a @test
  MethodError: kwcall(::@NamedTuple{dims::Int64}, ::typeof(ChainRulesCore.rrule), ::typeof(sum), ::BitVector) is ambiguous.
  
  Candidates:
    kwcall(::NamedTuple, ::typeof(ChainRulesCore.rrule), ::typeof(sum), x::AbstractArray)
      @ ChainRules ~/.julia/packages/ChainRules/WToPR/src/rulesets/Base/mapreduce.jl:28
    kwcall(kwargs, ::typeof(ChainRulesCore.rrule), ::typeof(sum), var"508"::AbstractArray{Bool})
      @ ChainRules none:0
  
  Possible fix, define
    kwcall(::NamedTuple, ::typeof(ChainRulesCore.rrule), ::typeof(sum), ::AbstractArray{Bool})
  
  Stacktrace:
    [1] kwcall(::@NamedTuple{dims::Int64}, ::typeof(ChainRulesCore.rrule), ::ChainRulesTestUtils.TestConfig, ::Function, ::BitVector)
      @ ChainRulesCore ~/.julia/packages/ChainRulesCore/iaCWL/src/rules.jl:140
    [2] _args_and_call(::ChainRulesTestUtils.TestConfig, ::Vararg{Any}; kwargs::@Kwargs{dims::Int64})
      @ Test ~/julia/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:1800
    [3] _test_inferred(::Any, ::Any, ::Vararg{Any}; kwargs...)
      @ ChainRulesTestUtils ~/.julia/packages/ChainRulesTestUtils/by7Dj/src/testers.jl:266
    [4] macro expansion
      @ ~/.julia/packages/ChainRulesTestUtils/by7Dj/src/testers.jl:210 [inlined]
    [5] macro expansion
      @ ~/julia/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:1598 [inlined]
    [6] test_rrule(config::ChainRulesCore.RuleConfig, f::Any, args::Any; output_tangent::Any, check_thunked_output_tangent::Any, fdm::Any, rrule_f::Any, check_inferred::Bool, fkwargs::NamedTuple, rtol::Real, atol::Real, testset_name::Any, kwargs...)
      @ ChainRulesTestUtils ~/.julia/packages/ChainRulesTestUtils/by7Dj/src/testers.jl:205
    [7] #test_rrule#62
      @ ~/.julia/packages/ChainRulesTestUtils/by7Dj/src/testers.jl:178 [inlined]
    [8] top-level scope
      @ REPL[8]:1
    [9] eval
      @ ./boot.jl:428 [inlined]
   [10] eval_user_input(ast::Any, backend::REPL.REPLBackend, mod::Module)
      @ REPL ~/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:224
   [11] repl_backend_loop(backend::REPL.REPLBackend, get_module::Function)
      @ REPL ~/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:320
   [12] start_repl_backend(backend::REPL.REPLBackend, consumer::Any; get_module::Function)
      @ REPL ~/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:305
   [13] run_repl(repl::REPL.AbstractREPL, consumer::Any; backend_on_current_task::Bool, backend::Any)
      @ REPL ~/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:461
   [14] run_repl(repl::REPL.AbstractREPL, consumer::Any)
      @ REPL ~/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:447
   [15] (::Base.var"#1096#1098"{Bool, Symbol, Bool})(REPL::Module)
      @ Base ./client.jl:440
   [16] #invokelatest#2
      @ ./essentials.jl:1020 [inlined]
   [17] invokelatest
      @ ./essentials.jl:1017 [inlined]
   [18] run_main_repl(interactive::Bool, quiet::Bool, banner::Symbol, history_file::Bool, color_set::Bool)
      @ Base ./client.jl:424
   [19] repl_main
      @ ./client.jl:561 [inlined]
   [20] _start()
      @ Base ./client.jl:535
Test Summary:                | Error  Total  Time
test_rrule: sum on BitVector |     1      1  0.9s
ERROR: Some tests did not pass: 0 passed, 0 failed, 1 errored, 0 broken.

[oxinabox]

Smaller MWE without CRTU

julia> rrule(sum, rand(4) .>0, dims=1)
ERROR: MethodError: kwcall(::@NamedTuple{dims::Int64}, ::typeof(rrule), ::typeof(sum), ::BitVector) is ambiguous.

Candidates:
  kwcall(::NamedTuple, ::typeof(rrule), ::typeof(sum), x::AbstractArray)
    @ ChainRules ~/JuliaEnvs/ChainRules.jl/src/rulesets/Base/mapreduce.jl:28
  kwcall(kwargs, ::typeof(rrule), ::typeof(sum), var"508"::AbstractArray{Bool})
    @ ChainRules none:0

Possible fix, define
  kwcall(::NamedTuple, ::typeof(rrule), ::typeof(sum), ::AbstractArray{Bool})

Stacktrace:
 [1] top-level scope
   @ REPL[5]:1

If we look at the relevant methods via methodswith(typeof(sum))
we can track down the actual methods causing the problem. (rather than the kwarg methods)
The particular ones are

[19] rrule(::typeof(sum), var"508"::AbstractArray{Bool}) @ ChainRules ~/JuliaEnvs/ChainRules.jl/src/rulesets/Base/nondiff.jl:80
[24] rrule(::typeof(sum), x::AbstractArray; dims) @ ChainRules ~/JuliaEnvs/ChainRules.jl/src/rulesets/Base/mapreduce.jl:28`

I am wondering if something in the @non_differentiable macro is lacking