[Issue 21709] New: std.conv.emplace not usable in betterC - 2.096 beta

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21709

          Issue ID: 21709
           Summary: std.conv.emplace not usable in betterC - 2.096 beta
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: regression
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: mmcomando at gmail.com

Our CI updated to dmd 2.096 and this error showed up:
/root/dlang/dmd-2.096.0/linux/bin64/../../src/druntime/import/core/internal/lifetime.d(35,13):
Error: Cannot use try-catch statements with -betterC
/root/dlang/dmd-2.096.0/linux/bin64/../../src/druntime/import/core/internal/lifetime.d(57,21):
Error: template instance `core.internal.lifetime.emplaceRef!(EntityManager,
EntityManager, uint, uint, uint).emplaceRef.S.__ctor!()` error instantiating

CI job url:
https://gitlab.com/mmcomando/bubel-ecs/-/jobs/1095299347

>From error message it seems that core.internal.lifetime.emplaceRef uses
try-catch statement which is not supported by -betterC.

I have tried to look for the code on github but I have not found lines with
try-catch in druntime/import/core/internal/lifetime.d(35,13) so I am not sure
if try-catch is the problem.

Part of our code which uses emplace:
    static T* make(T, Args...)(Args args)
    {
        T* ret = cast(T*) malloc(T.sizeof);
        static import std.conv;

        static if (__traits(isPOD, T))
        {
            __gshared immutable T init = T.init;
            memcpy(ret, &init, T.sizeof);
        }
        else static if (is(T == struct))
            std.conv.emplace(ret, args);
        return ret;
    }

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