Add compilefail test for Scope::create_nonstatic_userdata

tests/compile-fail/scope_userdata_borrow.rs

@@ -0,0 +1,24 @@
+extern crate rlua;
+
+use rlua::*;
+
+fn main() {
+    let lua = Lua::new();
+    let globals = lua.globals();
+
+    // Should not allow userdata borrow to outlive lifetime of AnyUserData handle
+    struct MyUserData<'a>(&'a i32);
+    impl<'a> UserData for MyUserData<'a> {};
+
+    let igood = 1;
+
+    let lua = Lua::new();
+    lua.scope(|scope| {
+        let ugood = scope.create_nonstatic_userdata(MyUserData(&igood)).unwrap();
+        let ubad = {
+            let ibad = 42;
+            scope.create_nonstatic_userdata(MyUserData(&ibad)).unwrap();
+            //~^ error: `ibad` does not live long enough
+        };
+    });
+}