Please be more careful when changing the language behavior

[Timon Gehr]

On 01.06.20 21:38, Johan wrote:
> Hi all,
>    Please be more careful when changing the language behavior.
> 
> The change made by https://github.com/dlang/dmd/pull/9289 silently 
> breaks code in ways that can be very hard to detect. We were lucky to 
> detect one case. There is no warning/deprecation whatsoever to warn me 
> about any other potential breakages in a heavily templated 400kloc 
> codebase with 212 instances of alias this.
> 
> The breakage introduced was very obvious, and warning about it is not 
> difficult either. We need to raise the bar for accepting changes like 
> this. The code on buildkite project tester is (fortunately) not the only 
> D code in the world.
> 
> Again, please be more careful when changing language behavior.
> 
> Thanks,
>    Johan
> 

Another example: 
https://github.com/dlang/dmd/commit/0f2889c3aa9fba5534e754dade0cae574b636d55#r36465193