@system blocks and safer @trusted (ST) functions

[Walter Bright]

On 7/25/2021 1:16 AM, Bruce Carneal wrote:
> He was the one who recommended that I 
> pursue this DIP at beerconf (it was just an idea that I'd thrown out up to that 
> point).

That's right. I did not think of the case of removing the @system block from a 
@trusted function and then silently losing the safety checking in the rest of 
the @trusted function. Thanks for pointing it out.

One solution would be for the compiler to check such @trusted functions for 
@safe-ty anyway, and issue an error for @trusted functions with no @system{} 
blocks and no @safe errors.

The user could silence this error by adding an empty @system block:

     @system { }