Code is only considered unreachable if it doesn't start with a throw statement

[jnm2]

Version Used: 16.0.0 RC.3

As expected:

void M()
{
    return;
    // CS0162 Unreachable code detected
    _ = 42;
    throw new NotImplementedException();
}

Broken:

void M()
{
    return;
    // No warning or transparency
    throw new NotImplementedException();
}

[YairHalberstadt]

That might be useful if you want to throw new InvalidOperationException("This location is thought to be unreachable");

[gafter]

The following types of statements are not reported as unreachable (by design)

• Block statements (however, statements within them may be reported unreachable)
• Throw statements
• Empty statements ;

We do this because that's what the older compiler did and we don't want to "break" existing code. I think these are justified philosophically, but in any case we won't change it.