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, 1 insertions, 0 deletions

diff --git a/tvix/eval/src/tests/nix_tests/eval-okay-mapattrs.exp b/tvix/eval/src/tests/nix_tests/eval-okay-mapattrs.exp
new file mode 100644
index 000000000000..3f113f17bab1
--- /dev/null
+++ b/tvix/eval/src/tests/nix_tests/eval-okay-mapattrs.exp
@@ -0,0 +1 @@
+{ x = "x-foo"; y = "y-bar"; }