move line decorator transformation out of the parser

moonscript/parse.lua

@@ -254,25 +254,7 @@ end
 -- transforms a statement that has a line decorator
 local function wrap_decorator(stm, dec)
 	if not dec then return stm end
-
-	local arg = {stm, dec}
-
-	if dec[1] == "if" then
-		local _, cond, fail = unpack(dec)
-		if fail then fail = {"else", {fail}} end
-		stm = {"if", cond, {stm}, fail}
-	elseif dec[1] == "unless" then
-		stm = {
-			"if",
-			{"not", {"parens", dec[2]}},
-			{stm}
-		}
-	elseif dec[1] == "comprehension" then
-		local _, clauses = unpack(dec)
-		stm = {"comprehension", stm, clauses}
-	end
-
-	return stm
+	return { "decorated", stm, dec }
 end
 
 -- wrap if statement if there is a conditional decorator

moonscript/transform.lua

@@ -549,6 +549,45 @@ Statement = Transformer({
     end
     return node
   end,
+  decorated = function(self, node)
+    local stm, dec = unpack(node, 2)
+    local _exp_0 = dec[1]
+    if "if" == _exp_0 then
+      local cond, fail = unpack(dec, 2)
+      if fail then
+        fail = {
+          "else",
+          {
+            fail
+          }
+        }
+      end
+      return {
+        "if",
+        cond,
+        {
+          stm
+        },
+        fail
+      }
+    elseif "unless" == _exp_0 then
+      return {
+        "unless",
+        dec[2],
+        {
+          stm
+        }
+      }
+    elseif "comprehension" == _exp_0 then
+      return {
+        "comprehension",
+        stm,
+        dec[2]
+      }
+    else
+      return error("Unknown decorator " .. dec[1])
+    end
+  end,
   unless = function(self, node)
     return {
       "if",

moonscript/transform.moon

@@ -244,6 +244,21 @@ Statement = Transformer {
     node[2] = apply_to_last node[2], ret if ret
     node
 
+  decorated: (node) =>
+    stm, dec = unpack node, 2
+
+    switch dec[1]
+      when "if"
+        cond, fail = unpack dec, 2
+        fail = { "else", { fail } } if fail
+        { "if", cond, { stm }, fail }
+      when "unless"
+        { "unless", dec[2], { stm } }
+      when "comprehension"
+        { "comprehension", stm, dec[2] }
+      else
+        error "Unknown decorator " .. dec[1]
+
   unless: (node) =>
     { "if", {"not", {"parens", node[2]}}, unpack node, 3 }