Code:

import std.stdio;
struct Foo {
    int val = 0;
        ~this() {
        writefln("destruct %s", val);
    }
}

void bar(ARGS...)() {
    ARGS args;
    args[0].val = 1;
    writefln("val = %s", args[0].val);
}

void main() {
    bar!Foo();
}

Excpected output:
val = 1
destruct 1

But got:
destruct 0
val = 1

It seems that the compiler destructs 'args' immediately after definition, not at the end of the function.

WORKAROUND:

import std.stdio;

struct Foo {
    int val = 0;
    ~this() {
        writefln("destruct %s", val);
    }
}

void bar(ARGS...)() {
    struct Tuple {
        ARGS args;
        alias args this;
    }
    Tuple args;
    args[0].val = 1;
    writefln("val = %s", args[0].val);
}


void main() {
    bar!Foo();
}

On 01/30/2017 12:55 PM, Jack Applegame wrote:
> Code:
>
> import std.stdio;
> struct Foo {
>     int val = 0;
>         ~this() {
>         writefln("destruct %s", val);
>     }
> }
>
> void bar(ARGS...)() {
>     ARGS args;
>     args[0].val = 1;
>     writefln("val = %s", args[0].val);
> }
>
> void main() {
>     bar!Foo();
> }
>
> Excpected output:
> val = 1
> destruct 1
>
> But got:
> destruct 0
> val = 1
>
> It seems that the compiler destructs 'args' immediately after
> definition, not at the end of the function.

Yup, looks like a (pretty bad) bug to me.

bug report: https://issues.dlang.org/show_bug.cgi?id=17128

On Monday, 30 January 2017 at 12:40:44 UTC, Jack Applegame wrote:
> bug report: https://issues.dlang.org/show_bug.cgi?id=17128

LDC (2.070.2) has a different problem: the dtor is never called.