This explicitly documents behavior of C++ Nix that goes against the
intuition you'd gather from this document: that e.g. a simple select
from an attribute set causes a value to no longer be pointer equal to
its former self.
The point of documenting this is that we can show in a to be written
section on the use of pointer equality in nixpkgs that pointer equality
is only needed in a limited sense for evaluating it (C++ Nix's exterior
pointer equality). Tvix's pointer equality is far more powerful since
value identity preserving operations also preserve pointer equality,
generally speaking (this is because we implement interior pointer
equality in my made up terminology). This should eventually also be
documented.
Change-Id: I6ce7ef2d67b012f5ebc92f9e81bba33fb9dce7d0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8856
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>
I want to expand on the C++ Nix behavior, since it seems relevant to
note that a lot of operations in C++ Nix (like select) don't preserve
pointer equality (see
<https://github.com/NixOS/nix/issues/3371#issuecomment-1596167957>).
It is especially so, as Tvix establishes pointer equality in a different
way and thus shows differing behavior. Therefore I want to additionally
document Tvix's current behavior and make it more explicit to what
extent nixpkgs needs pointer equality.
Change-Id: I9b4ba75dacb749c9fcbba4b9646c6b48bb57bbad
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8852
Autosubmit: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Main one is the its-it's mistake in the last paragraph, the rest was
suggested by LanguageTool.
Change-Id: If1b87a11f480452f312fc2759be7ded782d0a522
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7930
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
