Error with control flow

We've come across a strange bug involving control flow:

julia> using FiniteDifferences

julia> using Zygote

julia> function f(x)
         y = [[x]', [x]]
         r = 0.0
         o = 1.0
         for n in 1:2
           o *= y[n]
           if n < 2
             proj_o = o * [1.0]
           else
             # Error
             proj_o = o
             # Fix
             # proj_o = o * 1.0
           end
           r += proj_o
         end
         return r
       end
f (generic function with 1 method)

julia> x = 1.2
1.2

julia> f(x)
2.6399999999999997

julia> central_fdm(5, 1)(f, x)
3.4000000000000967

julia> f'(x)
ERROR: MethodError: no method matching +(::Float64, ::LinearAlgebra.Adjoint{Float64, Vector{Float64}})
For element-wise addition, use broadcasting with dot syntax: scalar .+ array
Closest candidates are:
  +(::Any, ::Any, ::Any, ::Any...) at ~/software/julia-1.7.3/share/julia/base/operators.jl:655
  +(::Union{Float16, Float32, Float64}, ::BigFloat) at ~/software/julia-1.7.3/share/julia/base/mpfr.jl:413
  +(::ChainRulesCore.Tangent{P}, ::P) where P at ~/.julia/packages/ChainRulesCore/GUvJT/src/tangent_arithmetic.jl:146
  ...
Stacktrace:
 [1] accum(x::Float64, y::LinearAlgebra.Adjoint{Float64, Vector{Float64}})
   @ Zygote ~/.julia/packages/Zygote/DkIUK/src/lib/lib.jl:17
 [2] Pullback
   @ ./REPL[16]:15 [inlined]
 [3] (::typeof(∂(f)))(Δ::Float64)
   @ Zygote ~/.julia/packages/Zygote/DkIUK/src/compiler/interface2.jl:0
 [4] (::Zygote.var"#52#53"{typeof(∂(f))})(Δ::Float64)
   @ Zygote ~/.julia/packages/Zygote/DkIUK/src/compiler/interface.jl:41
 [5] (::Zygote.var"#54#55"{typeof(f)})(x::Float64)
   @ Zygote ~/.julia/packages/Zygote/DkIUK/src/compiler/interface.jl:83
 [6] top-level scope
   @ REPL[20]:1

Changing the line:

proj_o = o

to:

proj_o = o * 1.0

fixes the issue and outputs:

julia> f(x)
2.6399999999999997

julia> central_fdm(5, 1)(f, x)
3.4000000000000967

julia> f'(x)
3.4000000000000004

Version information:

julia> versioninfo()
Julia Version 1.7.3
Commit 742b9abb4d (2022-05-06 12:58 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Xeon(R) E-2176M  CPU @ 2.70GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-12.0.1 (ORCJIT, skylake)
Environment:
  JULIA_EDITOR = vim

julia> using Pkg

julia> Pkg.status("Zygote")
      Status `~/.julia/environments/v1.7/Project.toml`
  [e88e6eb3] Zygote v0.6.40

julia> Pkg.status("ChainRules")
      Status `~/.julia/environments/v1.7/Project.toml`
  [082447d4] ChainRules v1.35.1

Original issue is here: https://github.com/ITensor/ITensorMPS.jl/issues/73