1 files changed, 36 insertions, 0 deletions

diff --git a/test/testdata/eval-fail-mutual-recursion.nix b/test/testdata/eval-fail-mutual-recursion.nix
new file mode 100644
index 0000000..d090d31
--- /dev/null
+++ b/test/testdata/eval-fail-mutual-recursion.nix
@@ -0,0 +1,36 @@
+# Check that stack frame deduplication only affects consecutive intervals, and
+# that they are reported independently of any preceding sections, even if
+# they're indistinguishable.
+#
+# In terms of the current implementation, we check that we clear the set of
+# "seen frames" after eliding a group of frames.
+#
+# Suppose we have:
+# - 10 frames in a function A
+# - 10 frames in a function B
+# - 10 frames in a function A
+#
+# We want to output:
+# - a few frames of A (skip the rest)
+# - a few frames of B (skip the rest)
+# - a few frames of A (skip the rest)
+#
+# If we implemented this in the naive manner, we'd instead get:
+# - a few frames of A (skip the rest)
+# - a few frames of B (skip the rest, _and_ skip the remaining frames of A)
+let
+  throwAfterB = recurse: n:
+    if n > 0
+    then throwAfterB recurse (n - 1)
+    else if recurse
+    then throwAfterA false 10
+    else throw "Uh oh!";
+
+  throwAfterA = recurse: n:
+    if n > 0
+    then throwAfterA recurse (n - 1)
+    else if recurse
+    then throwAfterB true 10
+    else throw "Uh oh!";
+in
+  throwAfterA true 10