Use compiler feedback for encoded relationships and appropriate observations for behavior the compiler cannot know. Ask which requirement gives an assertion its authority. Preserve legitimate behavior and compatibility; retire checks that only preserve a discarded private arrangement.
Why: implementation and test can repeat the same mistake. Counting tests, traits or passing checks does not establish the intended promise.
Consequence: use independent expectations where that risk matters, and report unexecuted checks honestly. An adapter invocation does not prove a real effect. If a project maintains negative compiler examples, they must fail at their claimed boundary with a working valid use in the same environment.
Projects decide whether and how to maintain such examples, and choose their own
development and release sequence. This doctrine neither requires nor bans
tests/ui, trybuild or another project-specific check. Human learning exercises
are judged by their designated human reviewer.