evaluator: repeated use of embedded disjunction results in "field not allowed"

[mvdan]

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

$ cue version
cue version v0.5.0-beta.5

go version devel go1.21-25f5d9d4a2 Sat Feb 4 07:03:16 2023 +0000
      -buildmode exe
       -compiler gc
     CGO_ENABLED 1
          GOARCH amd64
            GOOS linux
         GOAMD64 v3

Does this issue reproduce with the latest release?

No; the testscript below succeeds with v0.4.3.

What did you do?

exec cue-v0.4.3 export in.cue
cmp stdout stdout.golden

-- in.cue --
data: forms: [{
	fooID: "00-0000001"
}]

form1040: (#compute & {in: data}).out

#K1: {
	#_base: common: 3
	#FormFoo: {
		#_base
		fooID: string
	}
	#FormBar: {
		#_base
		barID: string
	}
	#Form: {
		#FormFoo | #FormBar
	}
}

#Input: {
	forms: [...#K1.#Form]
}

#summarizeReturn: {
	in:  #Input
	out: [ for k in in.forms { k.common } ]
}

#compute: {
	in:  #Input
	out: (#summarizeReturn & {"in": in}).out
}
-- stdout.golden --
{
    "data": {
        "forms": [
            {
                "fooID": "00-0000001"
            }
        ]
    },
    "form1040": [
        3
    ]
}

Somewhat reduced from @tmm1's code at https://github.com/tmm1/taxes.cue, where the original failure as of c7a9fefa2fa115b5d06fb952636a475823ff14a9 is:

$ make -C returns --always-make sample1
make: Entering directory '/home/mvdan/git/taxes2/returns'
make sample1.txt sample1.freefile
make[1]: Entering directory '/home/mvdan/git/taxes2/returns'
cue export cue: sample1.taxdata -fo sample1.taxdata.json
cue import -l data: -f sample1.taxdata.json
cue export --out cue compute.cue sample1.taxdata.cue -e '{"Form1040": Form1040}' > sample1.txt
in.k1s.0.partnershipEIN: field not allowed:
    ../return.cue:148:15
    ../k1.cue:4:10
    ../k1.cue:17:3
    ../k1.cue:18:3
    ../k1.cue:34:11
    ../k1.cue:35:3
    ../return.cue:19:8
    ../return.cue:19:11
    ../return.cue:46:8
    ../return.cue:146:14
    ../return.cue:147:14
    ../return.cue:148:41
    ./compute.cue:4:7
    ./compute.cue:6:40
    ./sample1.taxdata.cue:70:3
make[1]: *** [Makefile:20: sample1.txt] Error 1
rm sample1.taxdata.json sample1.taxdata.cue
make[1]: Leaving directory '/home/mvdan/git/taxes2/returns'
make: *** [Makefile:25: sample1] Error 2
make: Leaving directory '/home/mvdan/git/taxes2/returns'

What did you expect to see?

A successful testscript run.

What did you see instead?

> exec cue export in.cue
[stderr]
in.forms.0.fooID: field not allowed:
    ./in.cue:33:8
    ./in.cue:2:2
    ./in.cue:5:28
    ./in.cue:8:10
    ./in.cue:10:3
    ./in.cue:11:3
    ./in.cue:17:9
    ./in.cue:18:3
    ./in.cue:23:10
    ./in.cue:23:13
    ./in.cue:27:7
    ./in.cue:32:7
    ./in.cue:33:34
[exit status 1]

Worth noting that current CUE master, 02e19c8, also fails in the same way.

Here's a smaller reproducer, which again succeeds on v0.4.3 but fails on v0.5.0-beta.5:

exec cue export in.cue
cmp stdout stdout.golden

-- in.cue --
#FormFoo: fooID: string
#FormBar: barID: string
#Form: { #FormFoo | #FormBar }

data: {fooID: "123"}
out1: #Form & data
out2: #Form & out1
-- stdout.golden --
{
    "data": {
        "fooID": "123"
    },
    "out1": {
        "fooID": "123"
    },
    "out2": {
        "fooID": "123"
    }
}

Haven't bisected yet; will do so next.

[mvdan]

Bisected via:

git bisect start v0.5.0-beta.5 v0.4.3
git bisect run bash -c 'go install ./cmd/cue && testscript ~/src/cue/repro-cmd.txtar'

The result is https://review.gerrithub.io/c/cue-lang/cue/+/549079.

[mvdan]

cc @myitcv @mpvl; the regression seems to have been introduced while fixing #2209.