class inheritance

moonscript/compile/line.lua

@@ -209,7 +209,7 @@ line_compile = {
     return nil
   end,
   ["class"] = function(self, node)
-    local _, name, tbl = unpack(node)
+    local _, name, parent, tbl = unpack(node)
     local constructor = nil
     local final_properties = {  }
     local find_special
@@ -277,8 +277,20 @@ line_compile = {
             "slim",
             { { "raw", ("local self = setmetatable({}, %s)"):format(base_name) }, { "chain", "mt.__init", { "call", { "self", "..." } } }, "self" }
           } } } })
+    local parent_var = def_scope:free_name("parent")
+    if parent ~= "" then
+      def_scope:stm({ "if", parent_var, { { "chain", "setmetatable", { "call", { base_name, {
+                  "chain",
+                  "getmetatable",
+                  { "call", { parent_var } },
+                  { "dot", "__index" }
+                } } } } } })
+    end
     def_scope:add_line(("return setmetatable(%s, %s)"):format(cls, cls_mt))
-    local def = concat({ "(function()\n", (def_scope:render()), "\nend)()" })
+    if parent ~= "" then
+      parent = self:value(parent)
+    end
+    local def = concat({ ("(function(%s)\n"):format(parent_var), (def_scope:render()), ("\nend)(%s)"):format(parent) })
     return self:stm({ "assign", { name }, { def } })
   end,
   comprehension = function(self, node, action)

moonscript/compile/line.moon

@@ -161,7 +161,7 @@ line_compile =
     nil
 
   ["class"]: (node) =>
-    _, name, tbl = unpack node
+    _, name, parent, tbl = unpack node
 
     constructor = nil
     final_properties = {}
@@ -195,9 +195,6 @@ line_compile =
     dests = [{"self", name} for name in *self_args]
     insert body, 1, {"assign", dests, self_args} if #self_args > 0
 
-    -- insert body, 1, {"raw", ("local self = setmetatable({}, %s)"):format(mt_name)}
-    -- insert body, {"return", "self"}
-
     def_scope = @block()
     base_name = def_scope:free_name "base"
     def_scope:add_line ("local %s ="):format(base_name), def_scope:value tbl
@@ -216,9 +213,23 @@ line_compile =
         }}}
     }}
 
+    parent_var = def_scope:free_name "parent"
+    if parent != ""
+      def_scope:stm {"if", parent_var,
+        {{"chain", "setmetatable", {"call",
+        {base_name, {"chain", "getmetatable",
+          {"call", {parent_var}}, {"dot", "__index"}}}}}}}
+
     def_scope:add_line ("return setmetatable(%s, %s)"):format(cls, cls_mt)
 
-    def = concat { "(function()\n", (def_scope:render()), "\nend)()" }
+    parent = @value parent if parent != ""
+
+    def = concat {
+      ("(function(%s)\n"):format(parent_var)
+      (def_scope:render())
+      ("\nend)(%s)"):format(parent)
+    }
+
     @stm {"assign", {name}, {def}}
 
   comprehension: (node, action) =>

moonscript/parse.lua

@@ -340,8 +340,7 @@ local build_grammar = wrap(function()
 
 		TableBlock = Break * #Cmt(Indent, advance_indent) * TableBlockInner * OutBlock / mark"table",
 
-		ClassDecl = key"class" * Name * (key"extends" * Name)^-1 * TableBlock / mark"class",
-
+		ClassDecl = key"class" * Name * (key"extends" * Exp + C"")^-1 * TableBlock / mark"class",
 		Export = key"export" * Ct(NameList) / mark"export",
 
 		KeyValue = Ct((Name + sym"[" * Exp * sym"]") * symx":" * (Exp + TableBlock)),

tests/inputs/class.moon

@@ -11,4 +11,12 @@ x:hello()
 
 print x
 
+class Simple
+  cool: => print "cool"
+
+class Yikes extends Simple
+  new: => print "created hello"
+
+x = Yikes()
+x:cool()
 

tests/outputs/class.lua

@@ -1,4 +1,4 @@
-local Hello = (function()
+local Hello = (function(_parent_0)
   local _base_0 = { hello = function(self) return print(self.test, self.world) end, __tostring = function(self) return "hello world" end }
   _base_0.__index = _base_0
   return setmetatable({ __init = function(self, test, world)
@@ -12,4 +12,27 @@ local Hello = (function()
 end)()
 local x = Hello(1, 2)
 x:hello()
-print(x)
+print(x)
+local Simple = (function(_parent_0)
+  local _base_0 = { cool = function(self) return print("cool") end }
+  _base_0.__index = _base_0
+  return setmetatable({ __init = function(self) end }, { __index = _base_0, __call = function(mt, ...)
+      local self = setmetatable({}, _base_0)
+      mt.__init(self, ...)
+      return self
+    end })
+end)()
+local Yikes = (function(_parent_0)
+  local _base_0 = {  }
+  _base_0.__index = _base_0
+  if _parent_0 then
+    setmetatable(_base_0, getmetatable(_parent_0).__index)
+  end
+  return setmetatable({ __init = function(self) return print("created hello") end }, { __index = _base_0, __call = function(mt, ...)
+      local self = setmetatable({}, _base_0)
+      mt.__init(self, ...)
+      return self
+    end })
+end)(Simple)
+x = Yikes()
+x:cool()