Sample based on `Equivalence.onResultOf`:
Sample based on `Equivalence.onResultOf`:

- https://github.com/google/guava/blob/a5eb7fd6fbc3e5fdebe65f90dc6c41729f17b7b0/guava/src/com/google/common/base/Equivalence.java#L157
- https://github.com/google/guava/blob/a5eb7fd6fbc3e5fdebe65f90dc6c41729f17b7b0/guava/src/com/google/common/base/FunctionalEquivalence.java#L41

The current version of our hacky checker wrongly permits a call to the
constructor. The forthcoming version catches the mistake. I'll be
updating Guava accordingly.

jspecify/jspecify