False positive undefined variable warning with TimerOutputs.jl

[KristianHolme]

JET is warning about possible undefined variable when using the @timeit macro from TimerOutputs.jl.

MWE:

using TimerOutputs
using JET

module MWE
    using TimerOutputs: TimerOutput, @timeit

    "Simplest possible function that triggers the JET warning"
    function simple_timed()
        to = TimerOutput()
        @timeit to "section" begin
            42
        end
        return to
    end
end

using .MWE

report_simple = @report_call target_modules = (MWE,) MWE.simple_timed()
println(report_simple

this outputs

═════ 1 possible error found ═════
┌ simple_timed() @ Main.MWE /mypath/debug_timeroutputs.jl:11
│ local variable `accumulated_data#375` may be undefined: accumulated_data#375::TimerOutputs.TimeData
└────────────────────

The @timeitmacro expansion:

@timeit timer "label" begin
        body
end

expands to something like

  local_timer = timer
  enabled = local_timer.enabled        # Bool field on TimerOutput
  
  if enabled
      accumulated_data = push!(local_timer, "label")   # ← defined only here
  end
  
  t0 = time_ns()
  b0 = gc_bytes()
  
  try
      body
  finally
      if enabled
          do_accumulate!(accumulated_data, t0, b0)     # ← JET warns: may be undefined
          pop!(local_timer)
      end
  end

Should JET be able to understand that accumulated_data is never accessed when it is not defined?

Versioninfo

julia> versioninfo()
Julia Version 1.12.3
Commit 966d0af0fdf (2025-12-15 11:20 UTC)
Build Info:
Official https://julialang.org release
Platform Info:
OS: Linux (x86_64-linux-gnu)
CPU: 12 × 12th Gen Intel(R) Core(TM) i7-1255U
WORD_SIZE: 64
LLVM: libLLVM-18.1.7 (ORCJIT, alderlake)
GC: Built with stock GC
Threads: 12 default, 1 interactive, 12 GC (on 12 virtual cores)
Environment:
JULIA_EDITOR = code
JULIA_VSCODE_REPL = 1