Accessing an ArrayPartition through x doesn't work with VariableRateJump

Example:

function f(du,u,p,t)
  #du[1] = -u[1]
  du.x[1][1] = -u.x[1][1]  # ERROR here
end

u0 = ArrayPartition([1.0],[1.0])
ode = ODEProblem(f,u0,(0.0,1.0))

rate(u,p,t) = 10*u[1]
function affect!(integrator)
  #integrator.u[2] += randn()
  integrator.u.x[2] .+= randn() # ERROR here
end
jump = VariableRateJump(rate,affect!)
jump_prob = JumpProblem(ode,Direct(),jump)
sol = solve(jump_prob,Tsit5())

Results in:
type SubArray has no field x
inside the function f, where apparently u is of type SubArray{Float64,1,Array{Float64,1},Tuple{UnitRange{Int64}},true} rather than an ArrayPartition.
Replacing the offending line with the commented-out line in f, a similar exception appears in affect!:
type ExtendedJumpArray has no field x.
In the offending line is similarly replaced in affect!, it works as expected.

Reproduce the example with f, affect!, VariableRateJump, and JumpProblem, then trace how u becomes a SubArray and how the jump state becomes an ExtendedJumpArray. No source file or test is named, so begin by locating the callback and state-wrapping paths. Done means ArrayPartition state access through .x works in both callbacks without breaking ordinary indexing.