opAssign and const?

Era Scarecrow rtcvb32 at yahoo.com
Fri May 4 20:43:43 PDT 2012

On Saturday, 5 May 2012 at 03:32:06 UTC, Jonathan M Davis wrote:
> If you've declared an opAssign, I'd be very surprised if _any_  
> assignment worked which didn't work with the opAssign that you 
> declared.  Once you've declared an opAssign, you've taken over 
> the assignment  operator, and you need to define it for all of 
> the types that you want it to work with.

  So define all four... gotcha...

> According to http://dlang.org/function.html:
> ---------
> Func­tions are over­loaded based on how well the  
> ar­gu­ments to a func­tion can match up with the 
> pa­ra­me­ters. The func­tion with the  best match is 
> se­lected. The lev­els of match­ing are:
> 1. no match
> 2. match with im­plicit con­ver­sions
> 3. match with con­ver­sion to const
> 4. exact match
> ---------
> It picks opAssign(X) over opAssign(ref const X) with an 
> argument of type X,because opAssign(X) is an exact match (#4) 
> whereas opAssign(ref const X)requires a conversion to const 
> (#3).

  I guess there's one question left. Where does the struct live? 
If it closes at ending of the scope I believed that meant the 
stack, but then this would be illegal:

ref X func() {
   return X(new ubyte[5]); //reference to local variable!

  If it lives on the heap too rather than the stack, that'd good 
to know. I don't recall it specifying in TDPL, but it would be 
easy enough to assume it does (Coming from C).

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