lix/doc/manual/rl-next/nixversion-fake.md
Jade Lovelace 6d84d6bdc1 builtins: fix builtins.langVersion docs to state it's deprecated
This builtin was always a problem and nixpkgs uses it in exactly one
place, to give up if the Nix version is absurdly old. It has no other
use cases, and doesn't work in a multi-implementation world anyway.

Change-Id: I03c36e118591029e2ef14b091fe14a311c66a08a
2024-05-15 21:54:12 -07:00

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---
synopsis: "`builtins.nixVersion` and `builtins.langVersion` return fixed values"
cls: [558, 1144]
credits: jade
category: Breaking Changes
---
`builtins.nixVersion` now returns a fixed value `"2.18.3-lix"`.
`builtins.langVersion` returns a fixed value `6`, matching CppNix 2.18.
This prevents feature detection assuming that features that exist in Nix
post-Lix-branch-off might exist, even though the Lix version is greater than
the Nix version.
In the future, check for builtins for feature detection. If a feature cannot be
detected by *those* means, please file a Lix bug.