[fixed] super call in case where subclass called from doesn't have implementation - hurts runtime performance but the previous impl was a potential infinite loop!

class.lua

@@ -7,22 +7,24 @@
 
 local function class(inherits)
 	local c = {}
-	c.__mt = {
-		__index = c,
-	}
+	--class metatable
 	setmetatable(c, {
 		--wire up call as ctor
 		__call = function(self, ...)
 			return self:new(...)
 		end,
-		--handle single inheritence
+		--handle single inheritence chain
 		__index = inherits,
 	})
+	--instance metatable
+	c.__mt = {
+		__index = c,
+	}
 	--common class functions
 
 	--internal initialisation
 	--sets up an initialised object with a default value table
-	--performing a super construction if necessary and assigning the right metatable
+	--performing a super construction if necessary, and (re-)assigning the right metatable
 	function c:init(t, ...)
 		if inherits and inherits.new then
 			--construct superclass instance, then overlay args table
@@ -45,17 +47,38 @@ local function class(inherits)
 	--get the inherited class for super calls if/as needed
 	--allows overrides that still refer to superclass behaviour
 	function c:super()
-		return inherits or c
+		return inherits
 	end
 
 	--delegate a call to the superclass, by name
-	--still a bit clumsy but cleaner than the inline equivalent
+	--still a bit clumsy but much cleaner than the inline equivalent,
+	--plus handles heirarchical complications, and detects various mistakes
 	function c:super_call(func_name, ...)
-		local f = self:super()[func_name]
-		if f then
-			return f(self, ...)
+		--
+		assert(type(func_name) == "string", "super_call requires a string function name to look up")
+		--todo: memoize the below :)
+		local first_impl = c
+		--find the first superclass that actually has the method
+		while first_impl and not rawget(first_impl, func_name) do
+			first_impl = first_impl:super()
 		end
-		error("failed super call - missing function "..tostring(func_name).." in superclass")
+		if not first_impl then
+			error("failed super call - no superclass in the chain has an implementation of "..func_name)
+		end
+		--get the superclass of that
+		local super = first_impl:super()
+		if not super then
+			error("failed super call - no superclass to call from")
+		end
+
+		local f = super[func_name]
+		if not f then
+			error("failed super call - missing function "..func_name.." in superclass")
+		end
+		if f == self[func_name] then
+			error("failed super call - function "..func_name.." is same in superclass as in derived; this will be a infinite recursion!")
+		end
+		return f(self, ...)
 	end
 
 	--done