Trusted Manifesto

[via Digitalmars-d]

On Tuesday, 10 February 2015 at 15:57:28 UTC, Zach the Mystic 
wrote:
> On Tuesday, 10 February 2015 at 15:49:24 UTC, Zach the Mystic 
> wrote:
>>>> As already pointed out in the other thread, there is a 
>>>> non-breaking variant of (3):
>>>>
>>>> 3a. Keep named @trusted functions, allow @system blocks 
>>>> inside them, but only treat those with @system blocks with 
>>>> the new semantics.
>>>
>>> But they *have* no semantics without disallowing @system code 
>>> in the rest of the @trusted function.
>>
>> Wait a second... you're totally right. That is a cool 
>> solution. The only hiccup is that it might be hard to 
>> implement in the compiler because of flow tracking (i.e. the 
>> error comes before the @system block, forcing a recheck of all 
>> preceding functions.).
>
> I'm sorry I misread you at first -- this is actually really 
> cool (notwithstanding the hiccup)!

No problem!

At first I thought it was only a nice deprecation path, but I 
realised that the intermediate stage could even be kept 
indefinitely.

It probably wouldn't be too complicated to implement, because 
semantic analysis already happens in several stages. I think 
@safe checks happen relatively late, which means that there has 
already been one complete traversal of the functions AST which 
can take a note whenever it sees an @system block. If not, it 
would have to do a simple scan first, which doesn't seem to 
complicated either.