Compiler version

3.4.2 and 3.5.0-RC1, so probably all

Minimized code

With -Yexplicit-nulls and coverage enabled (project available at https://github.com/mohe2015/scala3-broken-coverage-explicit-nulls)

@main def hello(): Unit = println("Hello world!".nn)

Output

The expression is not marked as covered:

Expectation

All code is covered.