Computing the end line can error

[KristofferC]

julia> using JuliaInterpreter, Zygote, CodeTracking

julia> l, back = Zygote.forward(x -> sum(x), ones(10,10,10))
(1000.0, getfield(Zygote, Symbol("##71#72")){typeof(∂(getfield(Main, Symbol("##5#6"))()))}(∂(getfield(Main, Symbol("##5#6"))())))

julia> frame = JuliaInterpreter.enter_call(back, 1f0);

julia> frame, pc = JuliaInterpreter.debug_command(frame, :si);

julia> frame, pc = JuliaInterpreter.debug_command(frame, :si);

julia> frame, pc = JuliaInterpreter.debug_command(frame, :si);

julia> m = frame.framecode.scope; # showing this will crash Julia due to https://github.com/FluxML/Zygote.jl/issues/134

julia> m.name
:Pullback

julia> CodeTracking.definition(String, m)
ERROR: Base.Meta.ParseError("unexpected \"end\"")
Stacktrace:
 [1] #parse#1(::Bool, ::Bool, ::Bool, ::Function, ::String, ::Int64) at .\meta.jl:129
 [2] parse(::String, ::Int64) at .\meta.jl:121
 [3] definition(::Type{String}, ::Method) at C:\Users\Kristoffer\Debugging\Debugger\dev\CodeTracking\src\CodeTracking.jl:209
 [4] top-level scope at none:0

src is at this point equal to

ignore(T) = all(T -> T <: Type, T.parameters)

@generated function _forward(ctx::Context, f, args...)
  T = Tuple{f,args...}
  ignore(T) && return :(f(args...), Pullback{$T}(()))
  g = try _lookup_grad(T) catch e e end
  !(g isa Tuple) && return :(f(args...), Pullback{$T}((f,)))
  meta, forw, _ = g
  argnames!(meta, Symbol("#self#"), :ctx, :f, :args)
  forw = varargs!(meta, forw, 3)
  forw = slots!(pis!(inlineable!(forw)))
  return IRTools.update!(meta, forw)
end

@generated function (j::Pullback{T})(Δ) where T
  ignore(T) && return :nothing
  g = try _lookup_grad(T)
  catch e
    rethrow(CompileError(T,e))
  end
  if g == nothing
    Δ == Nothing && return :nothing
    return :(error("Non-differentiable function $(j.t[1])"))
  end
  meta, _, back = g
  resize!(back.argtypes, 2)
  argnames!(meta, Symbol("#self#"), :Δ)
  back = slots!(inlineable!(back))
  return IRTools.update!(meta, back)
end

with istart = 477 and then:

julia> print(s[477:end])
end

@generated function (j::Pullback{T})(Δ) where T
  ignore(T) && return :nothing
  g = try _
...

starts with an end.