DIP1028 - Rationale for accepting as is

[Paul Backus]

On Sunday, 24 May 2020 at 03:28:25 UTC, Walter Bright wrote:
> I'd like to emphasize:
>
> 1. It is not possible for the compiler to check any 
> declarations where the implementation is not available. Not in 
> D, not in any language. Declaring a declaration safe does not 
> make it safe.
>
> 2. If un-annotated declarations cause a compile time error, it 
> is highly likely the programmer will resort to "greenwashing" - 
> just slapping @safe on it. I've greenwashed code. Atila has. 
> Bruce Eckel has. We've all done it. Sometimes even for good 
> reasons.
>
> 3. Un-annotated declarations are easily detectable in a code 
> review.
>
> [...]

If we were designing a new language from scratch, I would agree 
100% with your reasoning.

The problem is that there are un-annotated declarations in 
existing code that have already been reviewed, committed, and 
published under the assumption of @system-by-default. Those 
declarations need to be flagged for re-review in order to avoid 
introducing silent safety violations to existing D projects.

To address this issue, I'm working on a PR to have dmd emit a 
diagnostic message when it encounters an un-annotated external 
function declaration. Feel free to drop by and comment:

https://github.com/dlang/dmd/pull/11176