feat(tvix/eval): Implement builtins.mapAttrs r/5192

I played around a little bit with doing this in-place, but ended up
going with this perhaps slightly clone-heavy approach for now because
ideally most clones on Value are cheap - but later we should benchmark
alternate approaches that get to reuse allocations better if necessary
or possible.

Change-Id: If998eb2056cedefdf2fb480b0568ac8329ccfc44
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7068
Autosubmit: grfn <grfn@gws.fyi>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

1 files changed, 10 insertions, 0 deletions

diff --git a/tvix/eval/src/value/attrs.rs b/tvix/eval/src/value/attrs.rs
index 17c7b422cb..c0f82b9214 100644
--- a/tvix/eval/src/value/attrs.rs
+++ b/tvix/eval/src/value/attrs.rs
@@ -517,3 +517,13 @@ impl<'a> Iterator for Keys<'a> {
         }
     }
 }
+
+impl<'a> IntoIterator for &'a NixAttrs {
+    type Item = (&'a NixString, &'a Value);
+
+    type IntoIter = Iter<KeyValue<'a>>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}