Automatically document builtin constants

This is done in roughly the same way builtin functions are documented.

Also auto-link experimental features for primops, subsuming PR #8371.

Co-authored-by: Eelco Dolstra <edolstra@gmail.com>
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>

3 files changed, 6 insertions, 44 deletions

diff --git a/doc/manual/src/language/builtin-constants-prefix.md b/doc/manual/src/language/builtin-constants-prefix.md
new file mode 100644
index 000000000..50f43006d
--- /dev/null
+++ b/doc/manual/src/language/builtin-constants-prefix.md
@@ -0,0 +1,5 @@
+# Built-in Constants
+
+These constants are built into the Nix language evaluator:
+
+<dl>
diff --git a/doc/manual/src/language/builtin-constants-suffix.md b/doc/manual/src/language/builtin-constants-suffix.md
new file mode 100644
index 000000000..a74db2857
--- /dev/null
+++ b/doc/manual/src/language/builtin-constants-suffix.md
@@ -0,0 +1 @@
+</dl>
diff --git a/doc/manual/src/language/builtin-constants.md b/doc/manual/src/language/builtin-constants.md
deleted file mode 100644
index 99520ad3f..000000000
--- a/doc/manual/src/language/builtin-constants.md
+++ /dev/null
@@ -1,44 +0,0 @@
-# Built-in Constants
-
-These constants are built into the Nix language evaluator:
-
-- [`builtins`]{#builtins-builtins} (attribute set)
-
-  Contains all the [built-in functions](./builtins.md) and values.
-
-  Since built-in functions were added over time, [testing for attributes](./operators.md#has-attribute) in `builtins` can be used for graceful fallback on older Nix installations:
-
-  ```nix
-  # if hasContext is not available, we assume `s` has a context
-  if builtins ? hasContext then builtins.hasContext s else true
-  ```
-
-- [`builtins.currentSystem`]{#builtins-currentSystem} (string)
-
-  The built-in value `currentSystem` evaluates to the Nix platform
-  identifier for the Nix installation on which the expression is being
-  evaluated, such as `"i686-linux"` or `"x86_64-darwin"`.
-
-  Not available in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).
-
-- [`builtins.currentTime`]{#builtins-currentTime} (integer)
-
-  Return the [Unix time](https://en.wikipedia.org/wiki/Unix_time) at first evaluation.
-  Repeated references to that name will re-use the initially obtained value.
-
-  Example:
-
-  ```console
-  $ nix repl
-  Welcome to Nix 2.15.1 Type :? for help.
-
-  nix-repl> builtins.currentTime
-  1683705525
-
-  nix-repl> builtins.currentTime
-  1683705525
-  ```
-
-  The [store path](@docroot@/glossary.md#gloss-store-path) of a derivation depending on `currentTime` will differ for each evaluation.
-
-  Not available in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).