evaluator: 'cycle error' reports no position information

[myitcv]

What version of CUE are you using (cue version)?

$ cue version
cue version v0.0.0-20240503105822-dff77a6d2a5a

go version go1.22.1
      -buildmode exe
       -compiler gc
  DefaultGODEBUG httplaxcontentlength=1,httpmuxgo121=1,tls10server=1,tlsrsakex=1,tlsunsafeekm=1
     CGO_ENABLED 1
          GOARCH arm64
            GOOS linux
             vcs git
    vcs.revision dff77a6d2a5a1133cedf2572dd9464fc62f62a16
        vcs.time 2024-05-03T10:58:22Z
    vcs.modified false
cue.lang.version v0.9.0

Does this issue reproduce with the latest release?

Yes

What did you do?

# new evaluator does output some position information
env CUE_EXPERIMENT='evalv3'
! exec cue export x.cue
stderr 'x\.cue'
cmp stderr new.golden

# old evaluator should output _some_ position information
env CUE_EXPERIMENT=''
! exec cue export x.cue
stderr 'x\.cue'

-- x.cue --
#TimeSpan: {
	start:    float
	duration: float
	end:      float

	start:    end - duration
	duration: end - start
	end:      start + duration

	start: <=end
}

examples: [string]: #TimeSpan

examples: eg1: {
    start: 10.0
    duration: 2.1
}

examples: eg2: {
    start: 10.0
}

examples: eg3: {
    end: 10.0
}
-- new.golden --
examples.eg2.start: non-concrete value end for bound <=:
    ./x.cue:10:11
examples.eg2.duration: non-concrete value float in operand to -:
    ./x.cue:7:12
    ./x.cue:4:12
examples.eg3.duration: non-concrete value <=10.0 & float in operand to -:
    ./x.cue:7:12

What did you expect to see?

Passing test.

What did you see instead?

# new evaluator does output some position information (0.014s)
# old evaluator should output _some_ position information (0.011s)
> env CUE_EXPERIMENT=''
> ! exec cue export x.cue
[stderr]
cycle error
[exit status 1]
> stderr 'x\.cue'
FAIL: /tmp/testscript203630098/repro.txtar/script.txtar:10: no match for `x\.cue` found in stderr

Is there perhaps something we can do with the old evaluator to output some position information here?

cc @b4nst