don't evaluate apply to last until the node is transormed

moonscript/compile/statement.lua

@@ -242,7 +242,8 @@ local statement_compilers = {
       _with_0:stms(node[2])
       return _with_0
     end
-  end
+  end,
+  noop = function(self) end
 }
 return {
   statement_compilers = statement_compilers

moonscript/compile/statement.moon

@@ -135,5 +135,7 @@ statement_compilers =
     with @block!
       \stms node[2]
 
+  noop: => -- nothing!
+
 
 { :statement_compilers }

moonscript/transform.lua

@@ -67,7 +67,11 @@ apply_to_last = function(stms, fn)
     local _len_0 = 1
     for i, stm in ipairs(stms) do
       if i == last_exp_id then
-        _accum_0[_len_0] = fn(stm)
+        _accum_0[_len_0] = {
+          "transform",
+          stm,
+          fn
+        }
       else
         _accum_0[_len_0] = stm
       end
@@ -331,6 +335,11 @@ construct_comprehension = function(inner, clauses)
   return current_stms[1]
 end
 local Statement = Transformer({
+  transform = function(self, tuple)
+    local _, node, fn
+    _, node, fn = tuple[1], tuple[2], tuple[3]
+    return fn(node)
+  end,
   root_stms = function(self, body)
     return apply_to_last(body, implicitly_return(self))
   end,
@@ -1354,7 +1363,9 @@ implicitly_return = function(scope)
       return scope.transform.statement(stm, fn)
     elseif types.manual_return[t] or not types.is_value(stm) then
       if is_top and t == "return" and stm[2] == "" then
-        return nil
+        return {
+          "noop"
+        }
       else
         return stm
       end

moonscript/transform.moon

@@ -32,7 +32,7 @@ apply_to_last = (stms, fn) ->
 
   return for i, stm in ipairs stms
     if i == last_exp_id
-      fn stm
+      {"transform", stm, fn}
     else
       stm
 
@@ -150,6 +150,10 @@ construct_comprehension = (inner, clauses) ->
   current_stms[1]
 
 Statement = Transformer {
+  transform: (tuple) =>
+    {_, node, fn} = tuple
+    fn node
+
   root_stms: (body) =>
     apply_to_last body, implicitly_return @
 
@@ -743,7 +747,7 @@ implicitly_return = (scope) ->
     elseif types.manual_return[t] or not types.is_value stm
       -- remove blank return statement
       if is_top and t == "return" and stm[2] == ""
-        nil
+        {"noop"}
       else
         stm
     else