* @-patterns as in Haskell. For instance, in a function definition

    f = args @ {x, y, z}: ...;

  `args' refers to the argument as a whole, which is further
  pattern-matched against the attribute set pattern {x, y, z}.

1 files changed, 16 insertions, 0 deletions

diff --git a/tests/lang/eval-okay-patterns.nix b/tests/lang/eval-okay-patterns.nix
new file mode 100644
index 000000000000..bcb9f3842e47
--- /dev/null
+++ b/tests/lang/eval-okay-patterns.nix
@@ -0,0 +1,16 @@
+let
+
+  f = args@{x, y, z}: x + args.y + z;
+
+  g = {x, y, z}@args: f args;
+
+  h = {x ? "d", y ? x, z ? args.x}@args: x + y + z;
+
+  i = args@args2: args.x + args2.y;
+
+in
+  f {x = "a"; y = "b"; z = "c";} +
+  g {x = "x"; y = "y"; z = "z";} +
+  h {x = "D";} +
+  h {x = "D"; y = "E"; z = "F";} +
+  i {x = "g"; y = "h";}