• Manu (2/2) Jan 20 2019 Does anyone understand: https://issues.dlang.org/show_bug.cgi?id=19598
• Simen =?UTF-8?B?S2rDpnLDpXM=?= (29/32) Jan 20 2019 Defining an opAssign for S seems to work:
• Simen =?UTF-8?B?S2rDpnLDpXM=?= (14/17) Jan 21 2019 So I spent a little time looking into this. It seems

Manu <turkeyman gmail.com> writes:

Does anyone understand: https://issues.dlang.org/show_bug.cgi?id=19598
And are there any known workarounds?

Simen =?UTF-8?B?S2rDpnLDpXM=?= <simen.kjaras gmail.com> writes:

On Monday, 21 January 2019 at 00:44:02 UTC, Manu wrote:
 Does anyone understand: 
 https://issues.dlang.org/show_bug.cgi?id=19598 And are there 
 any known workarounds?

Defining an opAssign for S seems to work:

int test()
{
     struct S { int x; void opAssign(S s) { x = s.x; } }
     S t1;
     S* n1 = new S;
     *n1 = t1;

     return 10;
}
pragma(msg, test());

Fascinatingly, it seems 'new' is doing something special in this 
code - replacing 'new S' with '&t1', things compile.

Second workaround: create an array of S, then take the address of 
the first one:

int test2()
{
     struct S { int x;  }
     S t1;
     S* n1 = &(new S[1])[0];
     *n1 = t1;

     return 10;
}
pragma(msg, test2());

Now, as for why the simple, sensible code in the bug report 
doesn't work, I have no idea. It seems `new S` marks the block in 
some way that prevents regular assignment from working.

--
   Simen

Simen =?UTF-8?B?S2rDpnLDpXM=?= <simen.kjaras gmail.com> writes:

On Monday, 21 January 2019 at 07:31:39 UTC, Simen Kjærås wrote:
 Now, as for why the simple, sensible code in the bug report 
 doesn't work, I have no idea. It seems `new S` marks the block 
 in some way that prevents regular assignment from working.

So I spent a little time looking into this. It seems 
assignToLvalue doesn't know how to deal with structs. I simply 
added this to dinterpret.d, around line 4026 (just before the 
"`%s` cannot be evaluated at compile time" block):

         else if (auto sle = e1.isStructLiteralExp())
         {
             oldval = sle;
         }

Now, is this a sufficient fix? I don't know. Does it break things 
elsewhere? I don't know. Does it work in this specific case, 
solving this specific problem? Sure does.

--
   Simen