Dicebot on leaving D: It is anarchy driven development in all its glory.

[Walter Bright]

On 8/25/2018 5:52 PM, David Nadlinger wrote:
> On Saturday, 25 August 2018 at 22:53:44 UTC, Walter Bright wrote:
>> On 8/25/2018 2:46 PM, David Nadlinger wrote:
>>> At least for the transition period, I'd have attributes only apply to the 
>>> user-specified code and infer them for the actual full constructor. (We can 
>>> still print a deprecation warning if they don't match.) —David
>>
>> Inferring is not good enough, for example:
>>
>> https://github.com/dlang/dmd/pull/6816#issuecomment-307972790
>>
>> There the @safe constructor is calling a destructor that calls free(). It 
>> can't be inferred as @safe.
> 
> How did you interpret "only apply to the user-specified code"? In this example, 
> the `@safe` in `this() @safe {}` would only apply to `{}`.

I'm not sure what you're referring to. I'm referring to the specified message, 
and the example:

struct Array
{
     int[] _payload;
     ~this() // (2)
     {
         import core.stdc.stdlib : free;
         free(_payload.ptr); // (3)
     }
}

class Scanner
{
     Array arr;
     this() @safe {}  // (1)
}

In order for (1) to be @safe, then the destructor it calls for arr (2) must also 
be @safe. But the destructor calls free() (3), which is not @safe. Therefore, 
the compilation fails. Inference does not solve this problem, because (2) is 
inferred as @system.


> can be supplemented with 
> deprecation warnings if the specified "inner" and inferred "outer" attributes 
> don't match.

Yes, and that's probably the only viable way forward with this. But Chris' ox 
will get gored, as 2009 code will not compile anymore without modification after 
the deprecation period expires.