From d63a5f5dd3b47e629295eb68264b4a6aadc65aa7 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 31 Mar 2022 17:33:06 +0200
Subject: [PATCH] Update release notes

---
 doc/manual/src/release-notes/rl-next.md | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md
index 2ec864ee4..4f3c9ce41 100644
--- a/doc/manual/src/release-notes/rl-next.md
+++ b/doc/manual/src/release-notes/rl-next.md
@@ -14,3 +14,21 @@
 
   This function is only available if you enable the experimental
   feature `fetch-closure`.
+
+* New experimental feature: *impure derivations*. These are
+  derivations that can produce a different result every time they're
+  built. Here is an example:
+
+  ```nix
+  stdenv.mkDerivation {
+    name = "impure";
+    __impure = true; # marks this derivation as impure
+    buildCommand = "date > $out";
+  }
+  ```
+
+  Running `nix build` twice on this expression will build the
+  derivation twice, producing two different content-addressed store
+  paths. Like fixed-output derivations, impure derivations have access
+  to the network. Only fixed-output derivations and impure derivations
+  can depend on an impure derivation.