Bug in dmd?

[Dukc]

On Tuesday, 14 June 2022 at 13:39:12 UTC, Andrey Zherikov wrote:
> I have [pretty simple code in my 
> library](https://github.com/andrey-zherikov/argparse/blob/bug/source/argparse/help.d#L27-L47):
> ```d
> alias CC = SumType!(AA,BB);
> struct AA {}
> struct BB
> {
>     CC[] c;
> }
>
> private void ppp(T, Output)(auto ref Output output, in 
> CommandArguments!T cmd, in Config config)
> {
>     auto cc = CC(AA());  // (1)
> }
> private void printHelp(T, Output)(auto ref Output output, in 
> CommandArguments!T cmd, in Config config)
> {
>     auto cc = CC(AA());  // (2)
> }
>
> void printHelp(T, Output)(auto ref Output output, in Config 
> config)
> {
>     ppp(output, CommandArguments!T(config), config);
>     printHelp(output, CommandArguments!T(config), config);
> }
> ```
>
> [Line (2) 
> produces](https://github.com/andrey-zherikov/argparse/runs/6880350900?check_suite_focus=true#step:5:12) `undefined reference to '_D3std7sumtype__T7SumTypeTS8argparse4help2AATSQtQm2BBZQBl6__dtorMFNaNbNiNfZv'` (it demangles to `pure nothrow @nogc @safe void std.sumtype.SumType!(argparse.help.AA, argparse.help.BB).SumType.__dtor()`)
>
> If I comment line (2) then everything is good (no link errors). 
> Note that there is the same code at (1) which doesn't produce 
> any error. Any idea what's going on?

No idea. The functions seems indeed to be exactly the same, so I 
assume this is a DMD bug. It cannot be a bug in `std.sumtype`, 
since that would trigger in both of the templates.

BTW, thanks for taking the effort to write your question this 
well (demagling, link to your library and all).