fix Vararg warning in test

[CarloLucibello]

Tests print a lot of

WARNING: Wrapping `Vararg` directly in UnionAll is deprecated (wrap the tuple instead).
You may need to write `f(x::Vararg{T})` rather than `f(x::Vararg{<:T})` or `f(x::Vararg{T}) where T` instead of `f(x::Vararg{T} where T)`.

We need to find the source of this and fix it

[ToucheSir]

Can we trigger a CI run with julia --depwarn=error to enumerate these?

[mcabbott]

Yes you can, xref JuliaLang/julia#56662

I think they are from inside Enzyme somewhere... ok I found where I looked, and the pointer was this line:

https://github.com/EnzymeAD/Enzyme.jl/blob/main/src/absint.jl#L98

on 23 November, at least:

Enzyme grad check Chain(Dense, Dense): Error During Test at /Users/me/.julia/dev/Flux/test/ext_enzyme/enzyme.jl:115
  Got exception outside of a @test
  Wrapping `Vararg` directly in UnionAll is deprecated (wrap the tuple instead).
  You may need to write `f(x::Vararg{T})` rather than `f(x::Vararg{<:T})` or `f(x::Vararg{T}) where T` instead of `f(x::Vararg{T} where T)`.
  Stacktrace:
    [1] UnionAll(v::TypeVar, t::Any)
      @ Core ./boot.jl:256
    [2] absint(arg::LLVM.CallInst, partial::Bool)
      @ Enzyme.Compiler ~/.julia/packages/Enzyme/RTS5U/src/absint.jl:98
    [3] abs_typeof(arg::LLVM.CallInst, partial::Bool, seenphis::Set{LLVM.PHIInst})
      @ Enzyme.Compiler ~/.julia/packages/Enzyme/RTS5U/src/absint.jl:716
    [4] abs_typeof(arg::LLVM.CallInst, partial::Bool)
      @ Enzyme.Compiler ~/.julia/packages/Enzyme/RTS5U/src/absint.jl:283
    [5] codegen(output::Symbol, job::GPUCompiler.CompilerJob{Enzyme.Compiler.EnzymeTarget, Enzyme.Compiler.EnzymeCompilerParams}; libraries::Bool, deferred_codegen::Bool, optimize::Bool, toplevel::Bool, strip::Bool, validate::Bool, only_entry::Bool, parent_job::Nothing)
      @ Enzyme.Compiler ~/.julia/packages/Enzyme/RTS5U/src/compiler.jl:7169
    [6] codegen
      @ ~/.julia/packages/Enzyme/RTS5U/src/compiler.jl:6146 [inlined]
    [7] _thunk(job::GPUCompiler.CompilerJob{Enzyme.Compiler.EnzymeTarget, Enzyme.Compiler.EnzymeCompilerParams}, postopt::Bool)
      @ Enzyme.Compiler ~/.julia/packages/Enzyme/RTS5U/src/compiler.jl:8468
    [8] _thunk
      @ ~/.julia/packages/Enzyme/RTS5U/src/compiler.jl:8468 [inlined]
    [9] cached_compilation
      @ ~/.julia/packages/Enzyme/RTS5U/src/compiler.jl:8509 [inlined]
   [10] thunkbase(ctx::LLVM.Context, mi::Core.MethodInstance, ::Val{0x0000000000007d08}, ::Type{Const{var"#loss#402"}}, ::Type{Active}, tt::Type{Tuple{Duplicated{Chain{Tuple{Dense{typeof(tanh), Matrix{Float32}, Vector{Float32}}, Dense{typeof(identity), Matrix{Float32}, Vector{Float32}}}}}, Duplicated{Vector{Float32}}}}, ::Val{Enzyme.API.DEM_ReverseModeCombined}, ::Val{1}, ::Val{(false, false, false)}, ::Val{true}, ::Val{false}, ::Type{EnzymeCore.FFIABI}, ::Val{true}, ::Val{false})
      @ Enzyme.Compiler ~/.julia/packages/Enzyme/RTS5U/src/compiler.jl:8641
   [11] #s2103#19072
      @ ~/.julia/packages/Enzyme/RTS5U/src/compiler.jl:8778 [inlined]
   [12] var"#s2103#19072"(FA::Any, A::Any, TT::Any, Mode::Any, ModifiedBetween::Any, width::Any, ReturnPrimal::Any, ShadowInit::Any, World::Any, ABI::Any, ErrIfFuncWritten::Any, RuntimeActivity::Any, ::Any, ::Type, ::Type, ::Type, tt::Any, ::Type, ::Type, ::Type, ::Type, ::Type, ::Type, ::Type, ::Any)
      @ Enzyme.Compiler ./none:0
   [13] (::Core.GeneratedFunctionStub)(::UInt64, ::LineNumberNode, ::Any, ::Vararg{Any})
      @ Core ./boot.jl:602
   [14] autodiff
      @ ~/.julia/packages/Enzyme/RTS5U/src/Enzyme.jl:473 [inlined]
   [15] autodiff(::EnzymeCore.ReverseMode{true, false, EnzymeCore.FFIABI, false, false}, ::var"#loss#402", ::Type{Active}, ::Duplicated{Chain{Tuple{Dense{typeof(tanh), Matrix{Float32}, Vector{Float32}}, Dense{typeof(identity), Matrix{Float32}, Vector{Float32}}}}}, ::Duplicated{Vector{Float32}})
      @ Enzyme ~/.julia/packages/Enzyme/RTS5U/src/Enzyme.jl:512
   [16] gradient_ez(::Function, ::Chain{Tuple{Dense{typeof(tanh), Matrix{Float32}, Vector{Float32}}, Dense{typeof(identity), Matrix{Float32}, Vector{Float32}}}}, ::Vararg{Any})
      @ Main ~/.julia/dev/Flux/test/ext_enzyme/enzyme.jl:30
   [17] test_enzyme_grad(loss::var"#loss#402", model::Chain{Tuple{Dense{typeof(tanh), Matrix{Float32}, Vector{Float32}}, Dense{typeof(identity), Matrix{Float32}, Vector{Float32}}}}, x::Vector{Float32})
      @ Main ~/.julia/dev/Flux/test/ext_enzyme/enzyme.jl:53

[CarloLucibello]

I think they are from inside Enzyme somewhere... ok I found where I looked, and the pointer was this line:
https://github.com/EnzymeAD/Enzyme.jl/blob/main/src/absint.jl#L98

@wsmoses can this be fixed?

[wsmoses]

Yeah, can you find a MWE so we can figure out how to fix?