[Issue 12684] New: Allow posblit elision when passing arguments to subfunctions

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12684

          Issue ID: 12684
           Summary: Allow posblit elision when passing arguments to
                    subfunctions
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: DMD
          Assignee: nobody at puremagic.com
          Reporter: monarchdodra at gmail.com

Similar to https://issues.dlang.org/show_bug.cgi?id=12683

Long story short:
//----
void redirect(T)(T t)
{
    bar(t); //Postblit here
}
void bar(T)(T t);
//----

Again, while I don't think we can elide the copy entirelly, I think we *can*
elide the postblit entirely.

Again, the reasons for allowing this are the same as 12683: There are *tons*
"redirect" functions that do nothing more than wrap a call to another
functions. The call to postblit is wasteful, and prevents usage with unique
objects.

Furthermore, this would be necessary for a more efficient "forward" template.
Currently, forward calls "T move(ref T t)". The "move" template in algorithm is
actually incredibly wasteful for types with postblits: It creates a 2
temporaries, it calls 2 memcopies, and it calls a destructor (on an object with
T.init state). *ALL* of this is exceedingly wasteful, for what should be
essentially be a no-op function...


Having this is necessary for fixing:
https://issues.dlang.org/show_bug.cgi?id=12628
emplace does not work for rvalues

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