schemachanger: add error-on-fallthrough guards on vistors

[bghal]

The issue in #169345 demonstrated the risk of switch statements on types
if an unexpected type is passed to the vistor function. This change
guards against future bugs by adding errors-on-default that trip on
unexpected types.

Epic: CRDB-31325

Informed by: #169345

Release note: None

[trunk-io]

😎 Merged successfully - details.

[cockroach-teamcity]

This change is 

[blathers-crl]

Detected infrastructure failure (matched: self-hosted runner lost communication with the server). Automatically rerunning failed jobs. (run link)

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[spilchen]

LGTM

[cockroach-teamcity]

⚪ Sysbench [SQL, 3node, oltp_read_write]

Metric	Old Commit	New Commit	Delta	Note
⚪ sec/op	10.19m ±1%	10.15m ±1%	~	p=0.539 n=15
⚪ allocs/op	8.123k ±0%	8.144k ±0%	~	p=0.300 n=15

Reproduce

benchdiff binaries:

mkdir -p benchdiff/cd36d28/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/cd36d28b77d439fd762a6795ca1fa90a4128d2d0/bin/pkg_sql_tests benchdiff/cd36d28/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/cd36d28/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
mkdir -p benchdiff/bca92f3/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/bca92f3b0e140f41ea2911e939d698e68eae8b06/bin/pkg_sql_tests benchdiff/bca92f3/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/bca92f3/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests

benchdiff command:

# NB: for best (most stable) results, also add a suitable `--benchtime` that
# results in ~1s to ~5s of benchmark runs. For example, if ops average ~3ms, a
# benchtime of `1000x` is appropriate.
#
# Some benchmarks (in particular BenchmarkSysbench) output additional memory
# profiles covering only the execution (excluding the setup/teardown) - those
# should be preferred for analysis since they more closely correspond to what's
# reported as B/op and alloc/op.
benchdiff --run=^BenchmarkSysbench/SQL/3node/oltp_read_write$ --old=bca92f3 --new=cd36d28 --memprofile ./pkg/sql/tests

⚪ Sysbench [KV, 3node, oltp_read_only]

Metric	Old Commit	New Commit	Delta	Note
⚪ sec/op	3.234m ±2%	3.294m ±1%	~	p=0.029 n=15
⚪ allocs/op	2.102k ±0%	2.102k ±0%	~	p=0.883 n=15

Reproduce

benchdiff binaries:

mkdir -p benchdiff/cd36d28/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/cd36d28b77d439fd762a6795ca1fa90a4128d2d0/bin/pkg_sql_tests benchdiff/cd36d28/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/cd36d28/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
mkdir -p benchdiff/bca92f3/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/bca92f3b0e140f41ea2911e939d698e68eae8b06/bin/pkg_sql_tests benchdiff/bca92f3/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/bca92f3/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests

benchdiff command:

# NB: for best (most stable) results, also add a suitable `--benchtime` that
# results in ~1s to ~5s of benchmark runs. For example, if ops average ~3ms, a
# benchtime of `1000x` is appropriate.
#
# Some benchmarks (in particular BenchmarkSysbench) output additional memory
# profiles covering only the execution (excluding the setup/teardown) - those
# should be preferred for analysis since they more closely correspond to what's
# reported as B/op and alloc/op.
benchdiff --run=^BenchmarkSysbench/KV/3node/oltp_read_only$ --old=bca92f3 --new=cd36d28 --memprofile ./pkg/sql/tests

🔴 Sysbench [KV, 3node, oltp_write_only]

Metric	Old Commit	New Commit	Delta	Note
🔴 sec/op	3.079m ±3%	3.199m ±3%	+3.88%	p=0.006 n=15
⚪ allocs/op	4.218k ±0%	4.221k ±0%	~	p=0.382 n=15

Reproduce

benchdiff binaries:

mkdir -p benchdiff/cd36d28/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/cd36d28b77d439fd762a6795ca1fa90a4128d2d0/bin/pkg_sql_tests benchdiff/cd36d28/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/cd36d28/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
mkdir -p benchdiff/bca92f3/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/bca92f3b0e140f41ea2911e939d698e68eae8b06/bin/pkg_sql_tests benchdiff/bca92f3/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/bca92f3/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests

benchdiff command:

# NB: for best (most stable) results, also add a suitable `--benchtime` that
# results in ~1s to ~5s of benchmark runs. For example, if ops average ~3ms, a
# benchtime of `1000x` is appropriate.
#
# Some benchmarks (in particular BenchmarkSysbench) output additional memory
# profiles covering only the execution (excluding the setup/teardown) - those
# should be preferred for analysis since they more closely correspond to what's
# reported as B/op and alloc/op.
benchdiff --run=^BenchmarkSysbench/KV/3node/oltp_write_only$ --old=bca92f3 --new=cd36d28 --memprofile ./pkg/sql/tests

Artifacts

download:

mkdir -p new
gcloud storage cp gs://cockroach-microbench-ci/artifacts/cd36d28b77d439fd762a6795ca1fa90a4128d2d0/25219761023-1/\* new/
mkdir -p old
gcloud storage cp gs://cockroach-microbench-ci/artifacts/bca92f3b0e140f41ea2911e939d698e68eae8b06/25219761023-1/\* old/

built with commit: cd36d28b77d439fd762a6795ca1fa90a4128d2d0

[bghal]

/trunk merge