#![no_main] breaks compiling with --test

[bjorn3]

I tried this code:

See title

I expected to see this happen: #![no_main] gets ignored as libtest can't possibly work with it.
Instead, this happened: A linker error complaining that main doesn't exist.

Meta

Someone hit this at https://users.rust-lang.org/t/error-when-testing-library/125842

[ChrisDenton]

The other option would be to error rather than ignore? Though that would require users to write #![cfg_attr(not(test), no_main)] or so.