eval: poor performance with large disjunction and matchIf

[rogpeppe]

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

$ cue version
2c6ed18e253b33ffe423d6781d1e4b9ac80a5e83

Does this issue reproduce with the latest stable release?

N/A (matchIf isn't present in the latest stable release)

What did you do?

exec time cue vet x.cue
-- x.cue --
import "list"

_schema & _data
_data: {
  "updates": [
    {
      "schedule": {
        "interval": "daily"
      }
    }
  ],
}

_schema: {
    matchIf(
        null | bool | number | string | [...] | {"enable-beta-ecosystems"!: true},
        _,
        null | bool | number | string | [...] | {
            "updates"?: null | bool | number | string | [...null | bool | number | string | [...] | {...}] | {...}
            ...
        }
    ) & {
        "updates"!: [...#update]
    }

    #update: {
        "schedule"!: {
            "timezone"?: #timezone
            ...
        }
        ...
    }

    // This was originally a list of 571 explicit time zones.
    #timezone: or([for i in list.Range(0, 571, 1) {"\(i)"}])
}

What did you expect to see?

A run that's reasonably quick.

What did you see instead?

> env CUE_STATS_FILE=stats.cue
> exec time cue vet x.cue
[stderr]
1.38user 0.02system 0:01.08elapsed 130%CPU (0avgtext+0avgdata 68736maxresident)k
0inputs+8outputs (0major+14150minor)pagefaults 0swaps
> exec cat stats.cue
[stdout]
CUE: {
	Unifications: 15633
	Disjuncts:    46583
	Conjuncts:    108394
	Freed:        46536
	Reused:       45955
	Allocs:       608
	Retained:     47
}
Go: {
	AllocBytes:   248382792
	AllocObjects: 9343904
}
PASS

This schema should not be taking over a second to evaluate.