Failure due to memcpy being called at compile time

[JG]

On Monday, 13 June 2022 at 20:25:00 UTC, Steven Schveighoffer 
wrote:
> On 6/13/22 4:09 PM, JG wrote:
>> Thanks. It seems to be something to do with the variadic 
>> template since this
>> works:
>> 
>> ```d
>> import std;
>> 
>> struct ParseError { string msg; }
>> 
>> alias ParseErrorOr(T) = SumType!(ParseError,T);
>> auto parseErrorOr(T)(T x) { return ParseErrorOr!T(x); }
>> 
>> auto parserOr(I,alias f, alias g)(I i) {
>>    auto cur = f(i);
>>    if(cur.match!((ParseError e)=>false,_=>true)) { return cur; 
>> }
>>    return g(i);
>> }
>> 
>> auto parseNothing(I)(I i) {
>>      return parseErrorOr(tuple(i[0..0],i));
>> }
>> 
>> void main()
>> {
>>      enum a = 
>> parserOr!(string,parseNothing!string,parseNothing!string)("hello");
>> }
>> ```
>
> Given that it's inside `moveEmplace`, I'd suspect something 
> deep in `SumType`.
>
> -Steve

Really strange. I can also work around it like this:

     ```d
     auto parserOr(I,fs...)(I i) if(fs.length>=2) {
       auto cur = fs[0](i);
       if(cur.match!((ParseError e)=>false,_=>true)) { return cur; 
}
       static if(fs.length==2) { return fs[1](i); }
       else { return parserOr!(I,fs[1..$])(i); }
     }
     ```