Failure due to memcpy being called at compile time

[Steven Schveighoffer]

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