fix Issue 23262 - typesafe variadic function parameter cannot infer r…

[WalterBright]

…eturn

[dlang-bot]

Thanks for your pull request, @WalterBright!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	23262	normal	typesafe variadic function parameter cannot infer return

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#14320"

[WalterBright]

Blocking #14319

[WalterBright]

The buildkite error:

CMake Error at cmake/Modules/FindLLVM.cmake:64 (message):
--
  | No LLVM installation (>= 9.0) found.  Try manually setting the
  | 'LLVM_ROOT_DIR' or 'LLVM_CONFIG' variables.

Doesn't look relevant to this PR.

[WalterBright]

@RazvanN7 the buildkite error is happening on other PRs. It's holding everything up.

[Geod24]

Workaround: dlang/ci#462

[dkorpel]

I think this can be refactored to avoid writing code for the parameter finding logic again, but for this PR it's fine.