Every other check in nix/checks.nix is a Rust derivation, so a
.nix-only diff moves no hash, the whole set is cache hits, and
`nix flake check` reports green without evaluating what changed.
`checks.module-eval` is one derivation holding a table of cases, each
named by the PROPERTY it defends. Its builder text embeds the evaluated
results, so the derivation's hash is a function of them: a nix change
that flips a property rebuilds the check and fails in the builder,
naming that property.
PROVEN, not assumed — the mechanism was executed before the cases were
written. Same expression with one property true vs false:
drvPath true -> 5v11mnbv…-module-eval.drv
drvPath false -> ivm3dvv8…-module-eval.drv (differs)
build false -> FAILS, stderr names the property
and the table itself was mutation-tested: inverting one case's
expectation gives `FAILED: a hive that has not opted into all-local
runs no swarm controller / module-eval: 1 of 5 properties broke`. A
check that cannot go red on a broken tree is not evidence.
Cases are named by property and never by ticket: a case named after the
ticket that prompted it has that ticket's lifetime; one named after the
property lives as long as the property does.
⚠️ It evaluates, it does not execute. Where the artifact is a command
line, a request or a certificate, a value assertion cannot stand in —
that is written into the file's header, because the gap is exactly what
made two earlier outages evaluable-but-broken.
