Added safety check to detect non-number keys in lists.

2 files changed, 9 insertions, 1 deletions

diff --git a/containers.lua b/containers.lua
index 09de4e5..9ebbf71 100644
--- a/containers.lua
+++ b/containers.lua
@@ -107,7 +107,11 @@ local _list_mt = {
       end
       return nil
     end
-  }
+  },
+  __newindex = function(self, k, v)
+    assert(type(k) == 'number', "List indices must be numbers")
+    return rawset(self, k, v)
+  end
 }
 list = function(t)
   return setmetatable(t, _list_mt)
diff --git a/containers.moon b/containers.moon
index deb5684..2441ccf 100644
--- a/containers.moon
+++ b/containers.moon
@@ -50,6 +50,10 @@ _list_mt =
                 if x == item
                     return i
             return nil
+    -- TODO: remove this safety check to get better performance?
+    __newindex: (k,v)=>
+        assert type(k) == 'number', "List indices must be numbers"
+        rawset(@, k, v)
 
 list = (t)-> setmetatable(t, _list_mt)