From 12edcd22c20f480ca73bcfdfb08477fb0480657d Mon Sep 17 00:00:00 2001
From: Alasdair
Date: Sun, 1 Nov 2020 15:00:11 +0000
Subject: Fix interpreter pattern matching bug

---
 src/interpreter.ml       |  2 +-
 test/c/empty_list.expect |  5 +++++
 test/c/empty_list.sail   | 21 +++++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 test/c/empty_list.expect
 create mode 100644 test/c/empty_list.sail

diff --git a/src/interpreter.ml b/src/interpreter.ml
index b0faabce..fb798b65 100644
--- a/src/interpreter.ml
+++ b/src/interpreter.ml
@@ -748,7 +748,7 @@ and pattern_match env (P_aux (p_aux, (l, _)) as pat) value =
         let hd_match, hd_bind = pattern_match env hd_pat hd_value in
         let tl_match, tl_bind = pattern_match env tl_pat (V_list tl_values) in
         hd_match && tl_match, Bindings.merge combine hd_bind tl_bind
-     | None -> failwith "Cannot match cons pattern against non-list"
+     | None -> false, Bindings.empty
      end
   | P_string_append _ -> assert false (* TODO *)
 
diff --git a/test/c/empty_list.expect b/test/c/empty_list.expect
new file mode 100644
index 00000000..e9c361a4
--- /dev/null
+++ b/test/c/empty_list.expect
@@ -0,0 +1,5 @@
+end
+.
+.
+.
+end
diff --git a/test/c/empty_list.sail b/test/c/empty_list.sail
new file mode 100644
index 00000000..a6ce0a91
--- /dev/null
+++ b/test/c/empty_list.sail
@@ -0,0 +1,21 @@
+default Order dec
+$include <prelude.sail>
+$include <string.sail>
+
+val list_test : list(int) -> unit
+
+function list_test(xs) =
+  match xs {
+    x :: xs => {
+      print_endline(".");
+      list_test(xs)
+    },
+    [||] => print_endline("end")
+  }
+
+val main : unit -> unit
+
+function main() = {
+  list_test([||]);
+  list_test([|1, 2, 3|])
+}
-- 
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