skinny delegates

[Steven Schveighoffer]

On 8/2/18 3:57 PM, kinke wrote:
> On Thursday, 2 August 2018 at 15:12:10 UTC, Steven Schveighoffer wrote:
>> On 8/2/18 11:00 AM, Kagamin wrote:
>>> I suppose it's mostly for mutability, so if it's const, it can be 
>>> optimized based on type information only:
>>>
>>> auto foo(in int x)
>>> {
>>>     return { return x + 10; };
>>> }
>>
>> I'm not sure what you mean here.
> 
> I think he's saying that the check for immutability could simply consist 
> in checking that all captured variables (well, not too much room for a 
> lot of them ;)) have a const type.

OK, yes, that's what I was thinking as well. On a 64-bit system, you 
could stuff 2 ints in there, which is a common theme for my code :)

> It's definitely an interesting idea, and the obvious benefit over a 
> library solution is that you wouldn't have to think about this 
> optimization when writing a delegate; if the captured stuff happens to 
> be const and fit into a pointer, the GC won't be bothered, nice.

Yeah, a library solution is opt-in, whereas if the compiler does it as 
an optimization, it's seamless (mostly invisible). And works in @nogc 
when possible.

-Steve