[Issue 8740] New: Temporary structs inside of array literals are destroyed and not copied in initialization of array

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=8740

           Summary: Temporary structs inside of array literals are
                    destroyed and not copied in initialization of array
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: dmitry.olsh at gmail.com


--- Comment #0 from Dmitry Olshansky <dmitry.olsh at gmail.com> 2012-09-30 07:32:49 PDT ---
See subject. Which is wrong and is unlike e.g. array append. 
Synposis:

version (msg) import std.stdio;
void main()
{
    struct Int
    {
        int* payload;
        this(int k)
        { 
            payload = new int; 
            *payload = k;
            version(msg) writeln("created: ", k);
        }
        this(this)
        {
            int* np = new int;
            *np = *payload;
            payload = np;
            version(msg) writeln("dupped: ", *payload);
        }
        ~this()
        {
            version(msg) writeln("destroyed: ", *payload);
            *payload = 0; //'destroy' it
        }
        @property int getPayload(){ return *payload; }        
        alias getPayload this;
    }
    //this destroys but not copies
    Int[] arr = [Int(1), Int(4), Int(5)]; 
    assert(arr[0] == 0); //passes while shouldn't (expected == 1)
    assert(arr[1] == 0); //ditto with 4
    assert(arr[2] == 0); //ditto with 5

    //this one does create/copy/destroy
    Int[] arr2;
    arr2 ~= [Int(1), Int(4), Int(5)]; // this copies things over unlike first
case
    assert(arr2[0] == 1);
    assert(arr2[1] == 4);
    assert(arr2[2] == 5);
}

Clearly Int[] arr = [...]; doesn't copy each element in turn, as is evident if
version=msg is specified:

created: 1
created: 4
created: 5
destroyed: 5
destroyed: 4
destroyed: 1
created: 1
created: 4
created: 5
dupped: 1
dupped: 4
dupped: 5
destroyed: 5
destroyed: 4
destroyed: 1

I argue that ideally the first and the 2nd version should just move temporaries
and never destroy them in the first place.
But minimally compiler should copy(dup) them in both cases if it can't figure
out how to move.

Compiler: DMD 2.061 as of git commit caf289137881ec290166afa72bc787bfbd6bd970

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