test(tvix/eval): verify pointer equality checks r/5369

Change-Id: I9baf2810fbd5b6ee8bfe10fce5b64801a35c1d67
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7369
Reviewed-by: tazjin <tazjin@tvl.su>
Reviewed-by: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI

2 files changed, 47 insertions, 0 deletions

diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-value-pointer-equality.exp b/tvix/eval/src/tests/tvix_tests/eval-okay-value-pointer-equality.exp
new file mode 100644
index 0000000000..aec30f297a
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-value-pointer-equality.exp
@@ -0,0 +1 @@
+[ true true true true false false false true true true true true true true true true false false ]
diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-value-pointer-equality.nix b/tvix/eval/src/tests/tvix_tests/eval-okay-value-pointer-equality.nix
new file mode 100644
index 0000000000..206881d7d9
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-value-pointer-equality.nix
@@ -0,0 +1,46 @@
+# For an explanation of this behavior see //tvix/docs/value-pointer-equality.md
+let
+  # Some incomparable values
+  f = MC: "Boing";
+  t = [ (throw "is a little blue man") ];
+  a = { "with" = abort "headphones and a big smile."; };
+
+  # Aliases
+  f' = f;
+  t' = t;
+  a' = a;
+
+  peq1 = a: b: [ a ] == [ b ];
+  peq2 = a: b: { x = a; } == { x = b; };
+in
+
+[
+  # pointer equality of functions
+  (peq1 f f)
+  (peq2 f f)
+  (peq1 f f')
+  (peq2 f f')
+
+  # encapsulation is necessary for pointer equality
+  (f == f)
+  (f == f')
+  # works with !=
+  ([ f ] != [ f' ])
+
+  # thunks that fail to evaluated wrapped in sets/lists
+  (peq1 t t)
+  (peq2 t t)
+  (peq1 a a)
+  (peq2 a a)
+  (peq1 t t')
+  (peq2 t t')
+  (peq1 a' a)
+  (peq2 a' a)
+
+  # function equality with builtins.elem
+  (builtins.elem f [ 21 f 42 ])
+
+  # pointer inequality
+  (peq1 f (x: x))
+  (peq2 (x: x) f)
+]
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