From 8ac27877e4e41c4000d1129d7fe598d9e81d5cea Mon Sep 17 00:00:00 2001
From: Timidger <APragmaticPlace@gmail.com>
Date: Tue, 7 Nov 2017 20:13:30 -0800
Subject: [PATCH 1/2] Only get gc on setmetatable if metatable isn't nil

---
 src/util.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/util.rs b/src/util.rs
index 788788b..41c76fc 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -512,7 +512,7 @@ pub unsafe extern "C" fn safe_setmetatable(state: *mut ffi::lua_State) -> c_int
     // Wrapping the __gc method in setmetatable ONLY works because Lua 5.3 only honors the __gc
     // method when it exists upon calling setmetatable, and ignores it if it is set later.
     push_string(state, "__gc");
-    if ffi::lua_rawget(state, -2) == ffi::LUA_TFUNCTION {
+    if ffi::lua_istable(state, -2) == 1 && ffi::lua_rawget(state, -2) == ffi::LUA_TFUNCTION {
         unsafe extern "C" fn safe_gc(state: *mut ffi::lua_State) -> c_int {
             ffi::lua_pushvalue(state, ffi::lua_upvalueindex(1));
             ffi::lua_insert(state, 1);

From f9c451bd267a02d455eda0e3d79c85e544adce1f Mon Sep 17 00:00:00 2001
From: Timidger <APragmaticPlace@gmail.com>
Date: Tue, 7 Nov 2017 20:13:52 -0800
Subject: [PATCH 2/2] Add test ensuring behaviour is correct

---
 src/tests.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/tests.rs b/src/tests.rs
index c2e3e00..e83b3ba 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -629,6 +629,16 @@ fn test_recursive_callback_panic() {
         .unwrap();
 }
 
+#[test]
+fn test_set_metatable_nil() {
+    let lua = Lua::new();
+    lua.exec::<()>(
+    r#"
+        a = {}
+        setmetatable(a, nil)
+    "#, None).unwrap();
+}
+
 // TODO: Need to use compiletest-rs or similar to make sure these don't compile.
 /*
 #[test]