If I use a final switch and import std.uni (or any other module that imports it, such as std.string), I'm getting unresolved external symbol errors with DMD 2.092.

This code triggers the issue:

---
module test;

import std.uni;

enum Cheese { cheddar, edam }

void test(Cheese cheese) {
  final switch (cheese) {
  case Cheese.cheddar: break;
  case Cheese.edam: break;
  }
}

void main() {
  test(Cheese.cheddar);
}
---

error LNK2019: unresolved external symbol "pure nothrow @nogc @safe void core.internal.switch_.__switch_error!().__switch_error(immutable(char)[], ulong)" (_D4core8internal7switch___T14__switch_errorZQrFNaNbNiNfAyamZv) referenced in function _Dmain

If I remove "final" and add a default case, it compiles fine. Is this a bug or have I made a mistake? This worked a few days ago and I haven't changed my setup since then.

On Sat, Jun 13, 2020 at 09:02:21AM +0000, John Chapman via Digitalmars-d-learn wrote: [...]
> module test;
> 
> import std.uni;
> 
> enum Cheese { cheddar, edam }
> 
> void test(Cheese cheese) {
>   final switch (cheese) {
>   case Cheese.cheddar: break;
>   case Cheese.edam: break;
>   }
> }
> 
> void main() {
>   test(Cheese.cheddar);
> }
> ---
> 
> error LNK2019: unresolved external symbol "pure nothrow @nogc @safe void
> core.internal.switch_.__switch_error!().__switch_error(immutable(char)[],
> ulong)" (_D4core8internal7switch___T14__switch_errorZQrFNaNbNiNfAyamZv)
> referenced in function _Dmain
[...]

Tested it on git master, DMD 2.091.1-beta.1 (Linux/64), could not
reproduce problem.

>From the error message, my first guess would be that your compiler and
druntime are out-of-sync somehow.


T

-- 
My father told me I wasn't at all afraid of hard work. I could lie down right next to it and go to sleep. -- Walter Bright

On Saturday, 13 June 2020 at 09:02:21 UTC, John Chapman wrote:
> Is this a bug or have I made a mistake? This worked a few days ago and I haven't changed my setup since then.

https://issues.dlang.org/show_bug.cgi?id=19548

Your code triggers it by using "-debug" option on https://run.dlang.io/ using DMD

On Saturday, 13 June 2020 at 15:33:55 UTC, Boris Carvajal wrote:
> On Saturday, 13 June 2020 at 09:02:21 UTC, John Chapman wrote:
>> Is this a bug or have I made a mistake? This worked a few days ago and I haven't changed my setup since then.
>
> https://issues.dlang.org/show_bug.cgi?id=19548
>
> Your code triggers it by using "-debug" option on https://run.dlang.io/ using DMD

Hmm, compiling with -release makes it work. Not a huge issue, I'll just avoid final switches in debug mode until it's fixed. Thanks.

On 6/13/20 9:22 AM, John Chapman wrote:

> Hmm, compiling with -release makes it work. Not a huge issue, I'll just avoid final switches in debug mode until it's fixed. Thanks.

Apparently, it's a known issue:

  https://issues.dlang.org/show_bug.cgi?id=19548

Ali

On Saturday, June 13, 2020 10:22:39 AM MDT John Chapman via Digitalmars-d- learn wrote:
> On Saturday, 13 June 2020 at 15:33:55 UTC, Boris Carvajal wrote:
> > On Saturday, 13 June 2020 at 09:02:21 UTC, John Chapman wrote:
> >> Is this a bug or have I made a mistake? This worked a few days ago and I haven't changed my setup since then.
> >
> > https://issues.dlang.org/show_bug.cgi?id=19548
> >
> > Your code triggers it by using "-debug" option on https://run.dlang.io/ using DMD
>
> Hmm, compiling with -release makes it work. Not a huge issue, I'll just avoid final switches in debug mode until it's fixed. Thanks.

Just be aware that that removes the code that gets generated which throws a SwitchError if the wrong value is passed to the final switch. So, instead of getting a SwitchError thrown, you'll get who-knows-what weird behavior happening if you have a bug with what you pass to the the switch (and of course, you lose assertions in general). It does sound like the problem that's resulting in the compilation error relates to the invisible default case that gets generated without -release though.

- Jonathan M Davis