Probably you are right, but for a library I think it should be an obligation to provide 100% coverage. For a generic program, maybe I sould provide 100% coverage at least of the "critical paths".

Might also be worth it to emphasize the "intended paths."

Of course, that is probably just saying that there should be documentation.

Especially given that you can't reasonably enforce the rigor of your test suite by way of your language.

Oddly, you could, in a way. Just treat your language and compiler as a tool in the toolchain. Add in a testing segment and you can set rules on it.