Nix integer overflow is implemented by undefined behavior

[roberth]

Describe the bug

See https://git.lix.systems/lix-project/lix/issues/423

1. Nix currently behaves by overflowing.
2. Overflowing is UB, but predictable, so a few users might rely on it without difficulties such as impurities showing through hashes and substitution

Steps To Reproduce

nix-repl> 500000000*50000000000
6553255926290448384

Expected behavior

I'm inclined to make it throw instead. If that is a problem, we may revisit. Have some thoughts on how; see https://git.lix.systems/lix-project/lix/issues/423#issuecomment-4604

nix-env --version output

Additional context

Priorities

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[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/2024-06-26-nix-team-meeting-minutes-156/47740/1