`the_derived_order_puts_primitives_last_and_that_wipes_screens` asserted that
switching primitives on still flattened at least one screen (`wiped_on > 0`),
and said to turn `include_primitives` on by default the day it stopped.
`53f8345` made that day arrive — a keyless primitive that would hide the screen
is now forced to paint first — and the wire had been red since 2026-08-29,
invisible to CI because the runner has no corpus and the suite self-skips.
#38 chose option A: keep the default off, and pin the fix instead. The flatness
proxy stood in for "paint order is solved", and the fix's own record says that
is only partly true — "This does **not** make `include_primitives` safe by
default" (docs/re/structures/ui-prm-primitives.md). So:
* renamed to `no_build_is_wiped_with_primitives_on` — the old name asserted
the bug; it survives in the doc comment for anyone searching from #38;
* `wiped_on > 0` -> `assert_eq!(wiped_on, 0)`, with a message saying what a
failure now means (`forced_backdrop` regressed) and that it must not be
"fixed" by turning primitives off in the test;
* `include_primitives` stays `false`; no library code changes.
It is the only end-to-end check of the rule: the four tests in
`ui_forced_backdrop_disc.rs` pin its mechanics, and none composes with
primitives on.
Verified with the corpus present, including that it can fail:
fix 3 passed 125 builds draw a primitive, 0 wiped
forced_backdrop disabled FAILED 36 of 125 wiped — the new message fired
restored 3 passed 125 builds, 0 wiped
The control's 36 is exactly the "36 builds ... wiped by our own sort" that
`53f8345` and `ui-forced-backdrop.md` report — the guard independently
reproduces the fix's own number, so it measures precisely what was repaired.
The control was a one-line `return false;` in a scratch copy; the working tree
was restored and `git diff` showed only this test file before committing.
Closes#38
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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