What should happen here?

[Ali Çehreli]

On 9/25/21 3:19 PM, Walter Bright wrote:
 > On 9/25/2021 10:46 AM, Steven Schveighoffer wrote:
 >> Right, but the optimizer is working against that.
 >>
 >> For example:
 >>
 >> ```d
 >> auto c = new C;
 >> .... // a whole bunch of other code
 >>
 >> c.method; // not necessarily still live here.
 >> ```
 >>
 >> Why would it not be live there? Because the method might be inlined,
 >> and the compiler might determine at that point that none of the data
 >> inside the method is needed, and therefore the object is no longer
 >> needed.
 >>
 >> So technically, it's not live after the original allocation. But this
 >> is really hard for a person to determine. Imagine having the GC
 >> collect your object when the object is clearly "used" later?
 >
 > I understand your point. It's value is never used again, so there is no
 > reason for the GC to hold on to it.

I must be misunderstanding Steven's example. You say "its value is never 
used again" yet his example has

   c.method

which to me is clearly "using" it again. So, I don't understand Steven's 
"not necessarily still live here" comment either. Is the case today?

 > After the point when the value is
 > never used again, when the destructor is run is indeterminate.

I accept that part.

The to-me-new concept of non-lexical scoping scares me if the 
non-lexical scope is shorter than lexical scope. And especially when the 
value is clearly used by `c.method`. (If I heard non-lexical scoping, I 
must have taken it as "destructor may be executed later than the lexical 
scope".)

Ali