Error using autodiff_thunk

[sethaxen]

Using autodiff_thunk on sum with a Const return activity results in an AssertionError:

x = [1.1, 2.2]
∂x = zero(x)

fwd, rev = autodiff_thunk(ReverseSplitWithPrimal, Const{typeof(sum)}, Active, Duplicated{typeof(x)});
tape, result, shadow_result = fwd(Const(sum), Duplicated(x, ∂x));
rev(Const(sum), Duplicated(x, ∂x), 1.0, tape)  # fine

fwd, rev = autodiff_thunk(ReverseSplitWithPrimal, Const{typeof(sum)}, Const, Duplicated{typeof(x)});
tape, result, shadow_result = fwd(Const(sum), Duplicated(x, ∂x));
rev(Const(sum), Duplicated(x, ∂x), 1.0, tape)  # error, see below

ERROR: AssertionError: length(argtypes) + needs_tape == length(argexprs)
Stacktrace:
 [1] #s295#184
   @ ~/projects/Enzyme.jl/src/compiler.jl:8357 [inlined]
 [2] var"#s295#184"(RawCall::Any, FA::Any, T::Any, RT::Any, TapeType::Any, N::Any, CC::Any, width::Any, returnPrimal::Any, ::Any, #unused#::Type, fptr::Any, #unused#::Type, #unused#::Type, #unused#::Type, tt::Any, rt::Any, fn::Any, #unused#::Any, args::Any)
   @ Enzyme.Compiler ./none:0
 [3] (::Core.GeneratedFunctionStub)(::Any, ::Vararg{Any})
   @ Core ./boot.jl:602
 [4] (::Enzyme.Compiler.AdjointThunk{Const{typeof(sum)}, Const{Float64}, Tuple{Duplicated{Vector{Float64}}}, Val{1}, Nothing})(::Const{typeof(sum)}, ::Duplicated{Vector{Float64}}, ::Vararg{Any})
   @ Enzyme.Compiler ~/projects/Enzyme.jl/src/compiler.jl:8308
 [5] top-level scope
   @ REPL[44]:1

[wsmoses]

You still pass the active return 1.0 in the second case, where you have the return marked as const.