DIP 1028---Make @safe the Default---Community Review Round 1

[Manu]

On Thu, Jan 9, 2020 at 12:34 PM H. S. Teoh via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
>
> On Thu, Jan 09, 2020 at 12:01:39PM +1000, Manu via Digitalmars-d wrote:
> > On Thu, Jan 9, 2020 at 10:49 AM H. S. Teoh via Digitalmars-d
> > <digitalmars-d at puremagic.com> wrote:
> [...]
> > >         auto myFunc() @safe {
> > >                 ... // mundane stuff
> > >                 () @trusted {
> > >                         // dangerous stuff goes here
> > >                 }();
> > >                 ... // more mundane stuff
> > >         }
> > >
> > > But it's quite the eyesore, I'll admit.
> [...]
> > Lambdas are usually suggested, but it's a completely unacceptable hack.
> >  * additional function call overhead
> >  * influences the inliner heuristics unfavourably
> >  * may allocate a closure if you're not careful
> [...]
>
> Oh? Didn't somebody post a PR to inline these lambdas when they appear
> in such contexts?  Was that never merged, or is it only active with
> -inline?  Did you check the output asm to see what it actually does?

That has never been behaviour I've observed. And GDC/LDC don't have
`-inline`; they defer to their own optimiser. LDC with -O2 doesn't
inline this.
I'm sure you can tickle the things and make this inline, but this will
still affect the compilers heuristics unfavourably leading to poor
optimisation choices regardless.

https://godbolt.org/z/oVdRP9

Abusing a lambda is not a 'feature', it's a terrible hack that
materially changes functionality and has never been a valid
suggestion. I've argued this so many times before.
We should have attributed scopes in the language, this has been a
feature request forever.