[Issue 18407] debug should escape nothrow, @nogc, @safe (not just pure)

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18407

--- Comment #2 from Timothee Cour <timothee.cour2 at gmail.com> ---
workaround suggested here by Adam Ruppe:
 https://forum.dlang.org/post/ojgxdtqodcamkqcrxgqc@forum.dlang.org
```
void foo() {}

@trusted nothrow @nogc void da(scope void delegate() a) {
        auto hack = cast(void delegate() @nogc) a;
        try
        hack();
        catch(Exception e)
                assert(0, e.msg);
}

@safe nothrow @nogc pure void main() {
        debug da({foo();});
}
```

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