diff --git a/code_obj.lua b/code_obj.lua
index 4fd01d6..376ee0c 100644
--- a/code_obj.lua
+++ b/code_obj.lua
@@ -110,9 +110,23 @@ do
       return self:text()
     end,
     as_lua = function(self)
-      return tostring(self.__class.__name) .. "(" .. tostring(concat({
-        tostring(self.source):as_lua(),
-        unpack((function()
+      if self.source then
+        return tostring(self.__class.__name) .. ":from(" .. tostring(concat({
+          tostring(self.source):as_lua(),
+          unpack((function()
+            local _accum_0 = { }
+            local _len_0 = 1
+            local _list_0 = self.bits
+            for _index_0 = 1, #_list_0 do
+              local b = _list_0[_index_0]
+              _accum_0[_len_0] = b:as_lua()
+              _len_0 = _len_0 + 1
+            end
+            return _accum_0
+          end)())
+        }, ", ")) .. ")"
+      else
+        return tostring(self.__class.__name) .. "(" .. tostring(concat((function()
           local _accum_0 = { }
           local _len_0 = 1
           local _list_0 = self.bits
@@ -122,8 +136,8 @@ do
             _len_0 = _len_0 + 1
           end
           return _accum_0
-        end)())
-      }, ", ")) .. ")"
+        end)(), ", ")) .. ")"
+      end
     end,
     __len = function(self)
       return #self:text()
@@ -246,12 +260,8 @@ do
   }
   _base_0.__index = _base_0
   _class_0 = setmetatable({
-    __init = function(self, source, ...)
-      self.source = source
+    __init = function(self, ...)
       self.bits = { }
-      if type(self.source) == 'string' then
-        self.source = Source:from_string(self.source)
-      end
       return self:append(...)
     end,
     __base = _base_0,
@@ -266,6 +276,14 @@ do
   })
   _base_0.__class = _class_0
   local self = _class_0
+  self.from = function(self, source, ...)
+    local inst = self(...)
+    if type(source) == 'string' then
+      source = Source:from_string(source)
+    end
+    inst.source = source
+    return inst
+  end
   self.is_instance = function(self, x)
     return type(x) == 'table' and x.__class == self
   end
@@ -370,27 +388,8 @@ do
       end
       return to_declare
     end,
-    as_statements = function(self, prefix, suffix)
-      if prefix == nil then
-        prefix = ""
-      end
-      if suffix == nil then
-        suffix = ";"
-      end
-      if self:text():matches(";$") or self:text() == "" then
-        return self
-      end
-      local statements = LuaCode(self.source)
-      if prefix ~= "" then
-        statements:append(prefix)
-      end
-      statements:append(self)
-      if suffix ~= "" then
-        statements:append(suffix)
-      end
-      return statements
-    end,
     make_offset_table = function(self)
+      assert(self.source, "This code doesn't have a source")
       local lua_to_nomsu, nomsu_to_lua = { }, { }
       local walk
       walk = function(lua, pos)
diff --git a/code_obj.moon b/code_obj.moon
index fcf2217..e7fb5f3 100644
--- a/code_obj.moon
+++ b/code_obj.moon
@@ -43,13 +43,17 @@ class Source
 
 class Code
     is_code: true
-    new: (@source, ...)=>
+    new: (...)=>
         @bits = {}
-        if type(@source) == 'string'
-            @source = Source\from_string(@source)
-        --assert(@source and Source\is_instance(@source), "Source has the wrong type")
         @append(...)
 
+    @from: (source, ...)=>
+        inst = self(...)
+        if type(source) == 'string'
+            source = Source\from_string(source)
+        inst.source = source
+        return inst
+
     @is_instance: (x)=> type(x) == 'table' and x.__class == @
 
     text: =>
@@ -71,7 +75,10 @@ class Code
     __tostring: => @text!
 
     as_lua: =>
-        "#{@__class.__name}(#{concat {tostring(@source)\as_lua!, unpack([b\as_lua! for b in *@bits])}, ", "})"
+        if @source
+            "#{@__class.__name}:from(#{concat {tostring(@source)\as_lua!, unpack([b\as_lua! for b in *@bits])}, ", "})"
+        else
+            "#{@__class.__name}(#{concat [b\as_lua! for b in *@bits], ", "})"
 
     __len: => #@text!
     
@@ -214,18 +221,8 @@ class LuaCode extends Code
             @prepend "local #{concat to_declare, ", "};\n"
         return to_declare
 
-    as_statements: (prefix="", suffix=";")=>
-        if @text!\matches(";$") or @text! == ""
-            return self
-        statements = LuaCode(@source)
-        if prefix != ""
-            statements\append prefix
-        statements\append self
-        if suffix != ""
-            statements\append suffix
-        return statements
-
     make_offset_table: =>
+        assert @source, "This code doesn't have a source"
         -- Return a mapping from output (lua) character number to input (nomsu) character number
         lua_to_nomsu, nomsu_to_lua = {}, {}
         walk = (lua, pos)->
diff --git a/compatibility/compatibility.nom b/compatibility/compatibility.nom
index 184ca56..4e22dbc 100644
--- a/compatibility/compatibility.nom
+++ b/compatibility/compatibility.nom
@@ -79,13 +79,13 @@ externally [..]
         if ((%ver as list) > (%end_version as list)): stop %ver
         if %ACTION_UPGRADES.%ver:
             %tree = (..)
-                %tree with % -> (..)
+                %tree with % ->:
                     if ((% is "Action" syntax tree) and %ACTION_UPGRADES.%ver.(%.stub)):
                         %with_upgraded_args = (..)
                             %k = (%v upgraded from %start_version to %end_version) for %k = %v in %
                         set %with_upgraded_args 's metatable to (% 's metatable)
                         return (..)
-                            call %ACTION_UPGRADES.%ver.(%.stub) with [%with_upgraded_args, %end_version]
+                            %ACTION_UPGRADES.%ver.(%.stub) %with_upgraded_args %end_version
         
         if %UPGRADES.%ver:
             %with_upgraded_args = (..)
diff --git a/containers.lua b/containers.lua
index 17d37a2..f33c2ff 100644
--- a/containers.lua
+++ b/containers.lua
@@ -210,19 +210,21 @@ local _list_mt = {
     end,
     from_1_to = function(self, start, stop)
       local n = #self
-      if n < 0 then
+      if start < 0 then
         start = (n + 1 - start)
       end
-      if n < 0 then
+      if stop < 0 then
         stop = (n + 1 - stop)
       end
-      local _accum_0 = { }
-      local _len_0 = 1
-      for i = start, stop do
-        _accum_0[_len_0] = self[i]
-        _len_0 = _len_0 + 1
-      end
-      return _accum_0
+      return List((function()
+        local _accum_0 = { }
+        local _len_0 = 1
+        for i = start, stop do
+          _accum_0[_len_0] = self[i]
+          _len_0 = _len_0 + 1
+        end
+        return _accum_0
+      end)())
     end
   },
   __newindex = function(self, k, v)
diff --git a/containers.moon b/containers.moon
index 4cafdaf..990a741 100644
--- a/containers.moon
+++ b/containers.moon
@@ -85,9 +85,9 @@ _list_mt =
             return nil
         from_1_to: (start, stop)=>
             n = #@
-            start = (n+1-start) if n < 0
-            stop = (n+1-stop) if n < 0
-            return [@[i] for i=start,stop]
+            start = (n+1-start) if start < 0
+            stop = (n+1-stop) if stop < 0
+            return List[@[i] for i=start,stop]
     -- TODO: remove this safety check to get better performance?
     __newindex: (k,v)=>
         assert type(k) == 'number', "List indices must be numbers"
diff --git a/core/control_flow.nom b/core/control_flow.nom
index cba0777..ff1a7c1 100644
--- a/core/control_flow.nom
+++ b/core/control_flow.nom
@@ -4,7 +4,6 @@
     like "if" statements and loops.
 
 use "core/metaprogramming.nom"
-use "core/text.nom"
 use "core/operators.nom"
 use "core/errors.nom"
 
diff --git a/core/io.nom b/core/io.nom
index edeeab4..2df0999 100644
--- a/core/io.nom
+++ b/core/io.nom
@@ -9,17 +9,17 @@ use "core/metaprogramming.nom"
 (say %message) compiles to:
     lua> "\
         ..if \%message.type == "Text" then
-            return LuaCode(tree.source, "print(", \(%message as lua expr), ");");
+            return LuaCode("print(", \(%message as lua expr), ");");
         else
-            return LuaCode(tree.source, "print(tostring(", \(%message as lua expr), "));");
+            return LuaCode("print(tostring(", \(%message as lua expr), "));");
         end"
 
 (ask %prompt) compiles to:
     lua> "\
         ..if \%prompt.type == "Text" then
-            return LuaCode(tree.source, "(io.write(", \(%prompt as lua expr), ") and io.read())");
+            return LuaCode("(io.write(", \(%prompt as lua expr), ") and io.read())");
         else
-            return LuaCode(tree.source, "(io.write(tostring(", \(..)
+            return LuaCode("(io.write(tostring(", \(..)
             %prompt as lua expr
         .., ")) and io.read())");
         end"
diff --git a/core/math.nom b/core/math.nom
index 1c7306e..8951721 100644
--- a/core/math.nom
+++ b/core/math.nom
@@ -85,7 +85,7 @@ externally [all of %items, all %items] all mean:
     return (yes)
 [all of %items, all %items] all compile to:
     unless (%items.type is "List"):
-        return %tree
+        return \(all of %items)
     if ((size of %items) == 0): return (Lua "true")
     %lua = (Lua "(")
     %lua::add ((% as lua expr) for % in %items) joined with " and "
@@ -99,7 +99,7 @@ externally [any of %items, any %items] all mean:
     return (no)
 [any of %items, any %items] all compile to:
     unless (%items.type is "List"):
-        return %tree
+        return \(any of %items)
     if ((size of %items) == 0): return (Lua "false")
     %lua = (Lua "(")
     %lua::add ((% as lua expr) for % in %items) joined with " or "
@@ -114,7 +114,7 @@ externally [sum of %items, sum %items] all mean:
     return %total
 [sum of %items, sum %items] all compile to:
     unless (%items.type is "List"):
-        return %tree
+        return \(sum of %items)
     if ((size of %items) == 0): return (Lua "0")
     %lua = (Lua "(")
     %lua::add ((% as lua expr) for % in %items) joined with " + "
@@ -127,7 +127,7 @@ externally [product of %items, product %items] all mean:
     return %prod
 [product of %items, product %items] all compile to:
     unless (%items.type is "List"):
-        return %tree
+        return \(product of %items)
     if ((size of %items) == 0): return (Lua "1")
     %lua = (Lua "(")
     %lua::add ((% as lua expr) for % in %items) joined with " * "
diff --git a/core/metaprogramming.nom b/core/metaprogramming.nom
index 1f787c2..fc81e15 100644
--- a/core/metaprogramming.nom
+++ b/core/metaprogramming.nom
@@ -17,13 +17,13 @@ lua> "\
             end
         end
     end
-    compile.action["define mangler"] = function(compile, tree)
-        return LuaCode(tree.source, "local mangle = mangler()")
+    compile.action["define mangler"] = function(compile)
+        return LuaCode("local mangle = mangler()")
     end"
 
 lua> "\
-    ..compile.action["1 ->"] = function(compile, tree, \%args, \%body)
-        local lua = LuaCode(tree.source, "(function(")
+    ..compile.action["1 ->"] = function(compile, \%args, \%body)
+        local lua = LuaCode("(function(")
         if SyntaxTree:is_instance(\%args) and \%args.type == "Action" then \%args = \%args:get_args() end
         local lua_args = table.map(\%args, function(a) return SyntaxTree:is_instance(a) and compile(a):text() or a end)
         lua:concat_append(lua_args, ", ")
@@ -36,11 +36,10 @@ lua> "\
     end"
 
 lua> "\
-    ..compile.action["what 1 compiles to"] = function(compile, tree, \%action)
-        local lua = LuaCode(tree.source, "compile.action[", \%action.stub:as_lua(), "](")
+    ..compile.action["what 1 compiles to"] = function(compile, \%action)
+        local lua = LuaCode("compile.action[", \%action.stub:as_lua(), "](")
         local lua_args = table.map(\%action:get_args(), function(a) return compile(a) end)
         table.insert(lua_args, 1, "compile")
-        table.insert(lua_args, 2, "tree")
         lua:concat_append(lua_args, ", ")
         lua:append(")")
         return lua
@@ -66,12 +65,12 @@ test:
     asdf
     assume (%tmp is (nil)) or barf "compile to is leaking variables"
 lua> "\
-    ..compile.action["1 compiles to"] = function(compile, tree, \%action, \%body)
-        local \%args = List{\(\%compile), \(\%tree), unpack(\%action:get_args())}
+    ..compile.action["1 compiles to"] = function(compile, \%action, \%body)
+        local \%args = List{\(\%compile), unpack(\%action:get_args())}
         if \%body.type == "Text" then
             \%body = SyntaxTree{source=\%body.source, type="Action", "Lua", \%body}
         end
-        return LuaCode(tree.source, "compile.action[", \%action.stub:as_lua(),
+        return LuaCode("compile.action[", \%action.stub:as_lua(),
             "] = ", \(what (%args -> %body) compiles to))
     end"
 
@@ -82,11 +81,11 @@ lua> "\
         ..if \%actions.type ~= "List" then
             compile_error(\%actions, "This should be a list of actions.")
         end
-        local lua = LuaCode(tree.source, \(what (%actions.1 compiles to %body) compiles to))
-        local \%args = List{\(\%compile), \(\%tree), unpack(\%actions[1]:get_args())}
+        local lua = \(what (%actions.1 compiles to %body) compiles to)
+        local \%args = List{\(\%compile), unpack(\%actions[1]:get_args())}
         for i=2,#\%actions do
             local alias = \%actions[i]
-            local \%alias_args = List{\(\%compile), \(\%tree), unpack(alias:get_args())}
+            local \%alias_args = List{\(\%compile), unpack(alias:get_args())}
             lua:append("\\ncompile.action[", alias.stub:as_lua(), "] = ")
             if \%alias_args == \%args then
                 lua:append("compile.action[", \%actions[1].stub:as_lua(), "]")
@@ -100,7 +99,7 @@ lua> "\
 
 (call %fn with %args) compiles to:
     lua> "\
-        ..local lua = LuaCode(tree.source, compile(\%fn), "(")
+        ..local lua = LuaCode(compile(\%fn), "(")
         if \%args.type == 'List' then
             lua:concat_append(table.map(\%args, function(a) return compile(a) end), ", ")
         else
@@ -126,14 +125,14 @@ test:
     lua> "\
         ..local fn_name = \%action.stub:as_lua_id()
         local \%args = \%action:get_args()
-        local lua = LuaCode(tree.source, fn_name, " = ", \(what (%args -> %body) compiles to))
+        local lua = LuaCode(fn_name, " = ", \(what (%args -> %body) compiles to))
         lua:add_free_vars({fn_name})
         return lua"
 (%actions all mean %body) compiles to:
     lua> "\
         ..local fn_name = \%actions[1].stub:as_lua_id()
         local \%args = List(\%actions[1]:get_args())
-        local lua = LuaCode(tree.source, \(what (%actions.1 means %body) compiles to))
+        local lua = \(what (%actions.1 means %body) compiles to)
         for i=2,#\%actions do
             local alias = \%actions[i]
             local alias_name = alias.stub:as_lua_id()
@@ -222,7 +221,7 @@ test:
                 return t:as_lua()
             end
         end
-        local \%new_body = LuaCode(\%body.source,
+        local \%new_body = LuaCode:from(\%body.source,
             "local mangle = mangler()",
             "\\nreturn ", make_tree(\%body))
         local ret = \(what (%actions all compile to %new_body) compiles to)
diff --git a/core/operators.nom b/core/operators.nom
index 38fc9a8..19a61d7 100644
--- a/core/operators.nom
+++ b/core/operators.nom
@@ -31,7 +31,7 @@ test:
     lua> "\
         ..local \%var_lua = \(%var as lua expr)
         local \%value_lua = \(%value as lua expr)
-        local lua = LuaCode(tree.source, \%var_lua, ' = ', \%value_lua, ';')
+        local lua = LuaCode(\%var_lua, ' = ', \%value_lua, ';')
         if \%var.type == 'Var' then
             lua:add_free_vars({compile(\%var):text()})
         end
@@ -49,7 +49,7 @@ test:
     assume (%assignments.type is "Dict") or barf "\
         ..Expected a Dict for the assignments part of '<- %' statement, not \%assignments"
     lua> "\
-        ..local lhs, rhs = LuaCode(tree.source), LuaCode(tree.source)
+        ..local lhs, rhs = LuaCode(), LuaCode()
         for i, item in ipairs(\%assignments) do
             local \%target, \%value = item[1], item[2]
             \%value = \%value:map(function(t)
@@ -69,7 +69,7 @@ test:
             lhs:append(target_lua)
             rhs:append(value_lua)
         end
-        return LuaCode(tree.source, lhs, " = ", rhs, ";")"
+        return LuaCode(lhs, " = ", rhs, ";")"
 
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -111,7 +111,7 @@ test:
 (with %assignments %body) compiles to:
     %lua = (%body as lua)
     lua> "\
-        ..local lhs, rhs = LuaCode(tree.source), LuaCode(tree.source)
+        ..local lhs, rhs = LuaCode(), LuaCode()
         local vars = {}
         for i, item in ipairs(\%assignments) do
             local \%target, \%value = item[1], item[2]
@@ -233,8 +233,7 @@ test:
 
 test:
     assume ((size of [1, 2, 3]) == 3)
-[size of %list, size of %list, size of %list, size of %list] all compile to (..)
-    "(#\(%list as lua expr))"
+(size of %list) compiles to "(#\(%list as lua expr))"
 
 (%list is empty) compiles to "(#\(%list as lua expr) == 0)"
 
diff --git a/core/text.nom b/core/text.nom
index 2d72f01..d4cd227 100644
--- a/core/text.nom
+++ b/core/text.nom
@@ -4,6 +4,8 @@
     color codes.
 
 use "core/metaprogramming.nom"
+use "core/operators.nom"
+use "core/control_flow.nom"
 
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -47,17 +49,9 @@ test:
     assume "\n" == (newline)
 
 # Text literals
-lua> "\
-    ..do
-        local escapes = {
-            nl="\\\\n", newline="\\\\n", tab="\\\\t", bell="\\\\a", cr="\\\\r",
-            ["carriage return"]="\\\\r", backspace="\\\\b", ["form feed"]="\\\\f",
-            formfeed="\\\\f", ["vertical tab"]="\\\\v",
-        };
-        for name, e in pairs(escapes) do
-            local lua = "'"..e.."'"
-            compile.action[name] = function(compile, tree)
-                return LuaCode(tree.source, lua)
-            end
-        end
-    end"
+%escapes = {..}
+    nl:"\n", newline:"\n", tab:"\t", bell:"\a", cr:"\r", "carriage return":"\r",
+    backspace:"\b", "form feed":"\f", formfeed:"\f", "vertical tab":"\v"
+for %name = %str in %escapes:
+    with {%lua: Lua (quote %str)}:
+        %compile.action.%name = ([]-> %lua)
diff --git a/lib/consolecolor.nom b/lib/consolecolor.nom
index d8b078f..1016c0b 100644
--- a/lib/consolecolor.nom
+++ b/lib/consolecolor.nom
@@ -17,7 +17,7 @@ for %name = %colornum in %colors:
     #(=lua "COMPILE_ACTIONS").%name = (..)
         [%nomsu, %tree] -> (Lua "'\\027[\(%colornum)m'")
     %compile.action.%name = (..)
-        [%nomsu, %tree, %text] ->:
+        [%nomsu, %text] ->:
             if %text:
                 return (Lua "('\\027[\(%colornum)m'..\(%text as lua expr)..'\\027[0m')")
             ..else: return (Lua "'\\027[\(%colornum)m'")
diff --git a/lib/object.nom b/lib/object.nom
index 2af5412..bb2de3a 100644
--- a/lib/object.nom
+++ b/lib/object.nom
@@ -56,7 +56,7 @@ test:
         ..local fn_name = \%actions[1].stub:as_lua_id()
         local \%args = List(\%actions[1]:get_args())
         table.insert(\%args, 1, \(\%me))
-        local lua = LuaCode(tree.source, "class.", fn_name, " = ", \(..)
+        local lua = LuaCode("class.", fn_name, " = ", \(..)
             what (%args -> %body) compiles to
         ..)
         for i=2,#\%actions do
diff --git a/lib/things.nom b/lib/things.nom
index 4f15e68..50c7aaa 100644
--- a/lib/things.nom
+++ b/lib/things.nom
@@ -60,7 +60,7 @@ test:
     lua> "\
         ..local fn_name = \%actions[1].stub:as_lua_id()
         local \%args = List{\(\%its), unpack(\%actions[1]:get_args())}
-        local lua = LuaCode(tree.source, "class.", fn_name, " = ", \(..)
+        local lua = LuaCode("class.", fn_name, " = ", \(..)
             what (%args -> %body) compiles to
         ..)
         for i=2,#\%actions do
diff --git a/nomsu.lua b/nomsu.lua
index 82c0d02..9010227 100644
--- a/nomsu.lua
+++ b/nomsu.lua
@@ -181,7 +181,7 @@ run = function()
         if args.check_syntax then
           local code = Files.read(filename)
           local source = Source(filename, 1, #code)
-          nomsu_environment._1_parsed(NomsuCode(source, code))
+          nomsu_environment._1_parsed(NomsuCode:from(source, code))
           print("Parse succeeded: " .. tostring(filename))
         elseif args.compile then
           local output
@@ -192,7 +192,7 @@ run = function()
           end
           local code = Files.read(filename)
           local source = Source(filename, 1, #code)
-          code = NomsuCode(source, code)
+          code = NomsuCode:from(source, code)
           local tree = nomsu_environment._1_parsed(code)
           if not (tree.type == 'FileChunks') then
             tree = {
@@ -214,7 +214,7 @@ run = function()
         elseif args.verbose then
           local code = Files.read(filename)
           local source = Source(filename, 1, #code)
-          code = NomsuCode(source, code)
+          code = NomsuCode:from(source, code)
           local tree = nomsu_environment._1_parsed(code)
           if not (tree.type == 'FileChunks') then
             tree = {
diff --git a/nomsu.moon b/nomsu.moon
index 8825ba5..35726e7 100755
--- a/nomsu.moon
+++ b/nomsu.moon
@@ -117,7 +117,7 @@ run = ->
                 -- Check syntax
                 code = Files.read(filename)
                 source = Source(filename, 1, #code)
-                nomsu_environment._1_parsed(NomsuCode(source, code))
+                nomsu_environment._1_parsed(NomsuCode\from(source, code))
                 print("Parse succeeded: #{filename}")
             elseif args.compile
                 -- Compile .nom files into .lua
@@ -125,7 +125,7 @@ run = ->
                 else io.open(filename\gsub("%.nom$", ".lua"), "w")
                 code = Files.read(filename)
                 source = Source(filename, 1, #code)
-                code = NomsuCode(source, code)
+                code = NomsuCode\from(source, code)
                 tree = nomsu_environment._1_parsed(code)
                 tree = {tree} unless tree.type == 'FileChunks'
                 for chunk in *tree
@@ -139,7 +139,7 @@ run = ->
             elseif args.verbose
                 code = Files.read(filename)
                 source = Source(filename, 1, #code)
-                code = NomsuCode(source, code)
+                code = NomsuCode\from(source, code)
                 tree = nomsu_environment._1_parsed(code)
                 tree = {tree} unless tree.type == 'FileChunks'
                 for chunk in *tree
diff --git a/nomsu_compiler.lua b/nomsu_compiler.lua
index d293d99..f262dd8 100644
--- a/nomsu_compiler.lua
+++ b/nomsu_compiler.lua
@@ -63,30 +63,11 @@ do
   tree_to_nomsu, tree_to_inline_nomsu = _obj_0.tree_to_nomsu, _obj_0.tree_to_inline_nomsu
 end
 local math_expression = re.compile([[ (([*/^+-] / [0-9]+) " ")* [*/^+-] !. ]])
-local compile_math_expression
-compile_math_expression = function(compile, tree, ...)
-  local lua = LuaCode(tree.source)
-  for i, tok in ipairs(tree) do
-    if type(tok) == 'string' then
-      lua:append(tok)
-    else
-      local tok_lua = compile(tok)
-      if tok.type == "Action" then
-        tok_lua:parenthesize()
-      end
-      lua:append(tok_lua)
-    end
-    if i < #tree then
-      lua:append(" ")
-    end
-  end
-  return lua
-end
 local MAX_LINE = 80
 local compile = setmetatable({
   action = Importer({
-    [""] = function(compile, tree, fn, ...)
-      local lua = LuaCode(tree.source)
+    [""] = function(compile, fn, ...)
+      local lua = LuaCode()
       local fn_lua = compile(fn)
       lua:append(fn_lua)
       if not (fn_lua:text():match("^%(.*%)$") or fn_lua:text():match("^[_a-zA-Z][_a-zA-Z0-9.]*$")) then
@@ -102,9 +83,9 @@ local compile = setmetatable({
       lua:append(")")
       return lua
     end,
-    ["Lua"] = function(compile, tree, code)
+    ["Lua"] = function(compile, code)
       if code.type ~= "Text" then
-        return LuaCode(code.source, "LuaCode(", tostring(code.source):as_lua(), ", ", compile(code), ")")
+        return LuaCode("LuaCode:from(", tostring(code.source):as_lua(), ", ", compile(code), ")")
       end
       local add_bit_lua
       add_bit_lua = function(lua, bit_lua)
@@ -114,7 +95,7 @@ local compile = setmetatable({
       end
       local operate_on_text
       operate_on_text = function(text)
-        local lua = LuaCode(text.source, "LuaCode(", tostring(text.source):as_lua())
+        local lua = LuaCode:from(text.source, "LuaCode:from(", tostring(text.source):as_lua())
         for _index_0 = 1, #text do
           local bit = text[_index_0]
           if type(bit) == "string" then
@@ -130,13 +111,13 @@ local compile = setmetatable({
       end
       return operate_on_text(code)
     end,
-    ["lua >"] = function(compile, tree, code)
+    ["lua >"] = function(compile, code)
       if code.type ~= "Text" then
-        return tree
+        return code
       end
       local operate_on_text
       operate_on_text = function(text)
-        local lua = LuaCode(text.source)
+        local lua = LuaCode:from(text.source)
         for _index_0 = 1, #text do
           local bit = text[_index_0]
           if type(bit) == "string" then
@@ -151,18 +132,18 @@ local compile = setmetatable({
       end
       return operate_on_text(code)
     end,
-    ["= lua"] = function(compile, tree, code)
-      return compile.action["lua >"](compile, tree, code)
+    ["= lua"] = function(compile, code)
+      return compile.action["lua >"](compile, code)
     end,
-    ["use"] = function(compile, tree, path)
-      return LuaCode(tree.source, "run_file_1_in(" .. tostring(compile(path)) .. ", _ENV)")
+    ["use"] = function(compile, path)
+      return LuaCode("run_file_1_in(" .. tostring(compile(path)) .. ", _ENV)")
     end,
-    ["tests"] = function(compile, tree)
-      return LuaCode(tree.source, "TESTS")
+    ["tests"] = function(compile)
+      return LuaCode("TESTS")
     end,
-    ["test"] = function(compile, tree, body)
+    ["test"] = function(compile, body)
       if not (body.type == 'Block') then
-        compile_error(tree, "This should be a Block")
+        compile_error(body, "This should be a Block")
       end
       local test_nomsu = body:get_source_code():match(":[ ]*(.*)")
       do
@@ -171,16 +152,16 @@ local compile = setmetatable({
           test_nomsu = test_nomsu:gsub("\n" .. indent, "\n")
         end
       end
-      return LuaCode(tree.source, "TESTS[" .. tostring(tostring(tree.source):as_lua()) .. "] = ", test_nomsu:as_lua())
+      return LuaCode("TESTS[" .. tostring(tostring(body.source):as_lua()) .. "] = ", test_nomsu:as_lua())
     end,
-    ["is jit"] = function(compile, tree, code)
-      return LuaCode(tree.source, "jit")
+    ["is jit"] = function(compile, code)
+      return LuaCode("jit")
     end,
-    ["Lua version"] = function(compile, tree, code)
-      return LuaCode(tree.source, "_VERSION")
+    ["Lua version"] = function(compile, code)
+      return LuaCode("_VERSION")
     end,
-    ["nomsu environment"] = function(compile, tree)
-      return LuaCode(tree.source, "_ENV")
+    ["nomsu environment"] = function(compile)
+      return LuaCode("_ENV")
     end
   })
 }, {
@@ -191,25 +172,27 @@ local compile = setmetatable({
     if force_value == nil then
       force_value = false
     end
-    if tree.version then
-      do
-        local get_version = compile.action[("Nomsu version"):as_lua_id()]
-        if get_version then
-          do
-            local upgrade = compile.action[("1 upgraded from 2 to"):as_lua_id()]
-            if upgrade then
-              tree = upgrade(tree, tree.version, get_version())
-            end
-          end
-        end
-      end
-    end
     local _exp_0 = tree.type
     if "Action" == _exp_0 then
       local stub = tree.stub
       local compile_action = compile.action[stub]
       if not compile_action and math_expression:match(stub) then
-        compile_action = compile_math_expression
+        local lua = LuaCode:from(tree.source)
+        for i, tok in ipairs(tree) do
+          if type(tok) == 'string' then
+            lua:append(tok)
+          else
+            local tok_lua = compile(tok)
+            if tok.type == "Action" then
+              tok_lua:parenthesize()
+            end
+            lua:append(tok_lua)
+          end
+          if i < #tree then
+            lua:append(" ")
+          end
+        end
+        return lua
       end
       if compile_action and not tree.target then
         local args
@@ -225,20 +208,21 @@ local compile = setmetatable({
           end
           args = _accum_0
         end
-        local ret = compile_action(compile, tree, unpack(args))
+        local ret = compile_action(compile, unpack(args))
         if ret == nil then
           local info = debug.getinfo(compile_action, "S")
           local filename = Source:from_string(info.source).filename
           compile_error(tree, "The compile-time action here (" .. tostring(stub) .. ") failed to return any value.", "Look at the implementation of (" .. tostring(stub) .. ") in " .. tostring(filename) .. ":" .. tostring(info.linedefined) .. " and make sure it's returning something.")
         end
         if not (SyntaxTree:is_instance(ret)) then
+          ret.source = ret.source or tree.source
           return ret
         end
         if ret ~= tree then
           return compile(ret)
         end
       end
-      local lua = LuaCode(tree.source)
+      local lua = LuaCode:from(tree.source)
       if tree.target then
         local target_lua = compile(tree.target)
         local target_text = target_lua:text()
@@ -269,7 +253,7 @@ local compile = setmetatable({
       lua:append(")")
       return lua
     elseif "EscapedNomsu" == _exp_0 then
-      local lua = LuaCode(tree.source, "SyntaxTree{")
+      local lua = LuaCode:from(tree.source, "SyntaxTree{")
       local needs_comma, i = false, 1
       local as_lua
       as_lua = function(x)
@@ -304,7 +288,7 @@ local compile = setmetatable({
       return lua
     elseif "Block" == _exp_0 then
       if not force_value then
-        local lua = LuaCode(tree.source)
+        local lua = LuaCode:from(tree.source)
         lua:concat_append((function()
           local _accum_0 = { }
           local _len_0 = 1
@@ -317,7 +301,7 @@ local compile = setmetatable({
         end)(), "\n")
         return lua
       else
-        local lua = LuaCode(tree.source)
+        local lua = LuaCode:from(tree.source)
         lua:append("((function()")
         for i, line in ipairs(tree) do
           lua:append("\n    ", compile(line))
@@ -326,7 +310,7 @@ local compile = setmetatable({
         return lua
       end
     elseif "Text" == _exp_0 then
-      local lua = LuaCode(tree.source)
+      local lua = LuaCode:from(tree.source)
       local string_buffer = ""
       for i, bit in ipairs(tree) do
         local _continue_0 = false
@@ -348,7 +332,7 @@ local compile = setmetatable({
             lua:append("..")
           end
           if bit.type ~= "Text" then
-            bit_lua = LuaCode(bit.source, "tostring(", bit_lua, ")")
+            bit_lua = LuaCode:from(bit.source, "tostring(", bit_lua, ")")
           end
           lua:append(bit_lua)
           _continue_0 = true
@@ -368,7 +352,7 @@ local compile = setmetatable({
       end
       return lua
     elseif "List" == _exp_0 or "Dict" == _exp_0 then
-      local lua = LuaCode(tree.source, tostring(tree.type) .. "{")
+      local lua = LuaCode:from(tree.source, tostring(tree.type) .. "{")
       local i = 1
       local sep = ''
       while i <= #tree do
@@ -389,32 +373,38 @@ local compile = setmetatable({
       end
       lua:append("}")
       if i <= #tree then
-        lua = LuaCode(tree.source, "(function()\n    local it = ", lua)
+        lua = LuaCode:from(tree.source, "(function()\n    local comprehension = ", lua)
+        if tree.type == "List" then
+          lua:append("\n    local function add(x) comprehension[#comprehension+1] = x end")
+        else
+          lua:append("\n    local function " .. tostring(("add 1 ="):as_lua_id()) .. "(k, v) comprehension[k] = v end")
+        end
         while i <= #tree do
           lua:append("\n    ")
           if tree[i].type == 'Block' or tree[i].type == 'Comment' then
             lua:append(compile(tree[i]))
           elseif tree[i].type == "DictEntry" then
-            lua:append("it[ ", compile(tree[i][1]), "] = ", (tree[i][2] and compile(tree[i][2]) or "true"))
+            local entry_lua = compile(tree[i])
+            lua:append((entry_lua:text():sub(1, 1) == '[' and "comprehension" or "comprehension."), entry_lua)
           else
-            lua:append("it:add(", compile(tree[i]), ")")
+            lua:append("comprehension[#comprehension+1] = ", compile(tree[i]))
           end
           i = i + 1
         end
-        lua:append("\n    return it\nend)()")
+        lua:append("\n    return comprehension\nend)()")
       end
       return lua
     elseif "DictEntry" == _exp_0 then
       local key, value = tree[1], tree[2]
       local key_lua = compile(key)
-      local value_lua = value and compile(value) or LuaCode(key.source, "true")
+      local value_lua = value and compile(value) or LuaCode:from(key.source, "true")
       local key_str = match(key_lua:text(), [=[^["']([a-zA-Z_][a-zA-Z0-9_]*)['"]$]=])
       if key_str and key_str:is_lua_id() then
-        return LuaCode(tree.source, key_str, "=", value_lua)
+        return LuaCode:from(tree.source, key_str, "=", value_lua)
       elseif sub(key_lua:text(), 1, 1) == "[" then
-        return LuaCode(tree.source, "[ ", key_lua, "]=", value_lua)
+        return LuaCode:from(tree.source, "[ ", key_lua, "]=", value_lua)
       else
-        return LuaCode(tree.source, "[", key_lua, "]=", value_lua)
+        return LuaCode:from(tree.source, "[", key_lua, "]=", value_lua)
       end
     elseif "IndexChain" == _exp_0 then
       local lua = compile(tree[1])
@@ -437,13 +427,13 @@ local compile = setmetatable({
       end
       return lua
     elseif "Number" == _exp_0 then
-      return LuaCode(tree.source, tostring(tree[1]))
+      return LuaCode:from(tree.source, tostring(tree[1]))
     elseif "Var" == _exp_0 then
-      return LuaCode(tree.source, (tree[1]):as_lua_id())
+      return LuaCode:from(tree.source, (tree[1]):as_lua_id())
     elseif "FileChunks" == _exp_0 then
       return error("Can't convert FileChunks to a single block of lua, since each chunk's " .. "compilation depends on the earlier chunks")
     elseif "Comment" == _exp_0 then
-      return LuaCode(tree.source, "")
+      return LuaCode:from(tree.source, "")
     elseif "Error" == _exp_0 then
       return error("Can't compile errors")
     else
diff --git a/nomsu_compiler.moon b/nomsu_compiler.moon
index 847da21..97cb0a7 100644
--- a/nomsu_compiler.moon
+++ b/nomsu_compiler.moon
@@ -40,23 +40,12 @@ compile_error = (tree, err_msg, hint=nil)->
 -- math expressions like 2*x + 3^2 without having to define a single
 -- action for every possibility.
 math_expression = re.compile [[ (([*/^+-] / [0-9]+) " ")* [*/^+-] !. ]]
-compile_math_expression = (compile, tree, ...)->
-    lua = LuaCode(tree.source)
-    for i,tok in ipairs tree
-        if type(tok) == 'string'
-            lua\append tok
-        else
-            tok_lua = compile(tok)
-            tok_lua\parenthesize! if tok.type == "Action"
-            lua\append tok_lua
-        lua\append " " if i < #tree
-    return lua
 
 MAX_LINE = 80 -- For beautification purposes, try not to make lines much longer than this value
 compile = setmetatable({
     action: Importer{
-        [""]: (compile, tree, fn, ...)->
-            lua = LuaCode(tree.source)
+        [""]: (compile, fn, ...)->
+            lua = LuaCode!
             fn_lua = compile(fn)
             lua\append fn_lua
             unless fn_lua\text!\match("^%(.*%)$") or fn_lua\text!\match("^[_a-zA-Z][_a-zA-Z0-9.]*$")
@@ -68,15 +57,15 @@ compile = setmetatable({
             lua\append ")"
             return lua
 
-        ["Lua"]: (compile, tree, code)->
+        ["Lua"]: (compile, code)->
             if code.type != "Text"
-                return LuaCode(code.source, "LuaCode(", tostring(code.source)\as_lua!, ", ", compile(code), ")")
+                return LuaCode("LuaCode:from(", tostring(code.source)\as_lua!, ", ", compile(code), ")")
             add_bit_lua = (lua, bit_lua)->
                 bit_leading_len = #(bit_lua\match("^[^\n]*"))
                 lua\append(lua\trailing_line_len! + bit_leading_len > MAX_LINE and ",\n    " or ", ")
                 lua\append(bit_lua)
             operate_on_text = (text)->
-                lua = LuaCode(text.source, "LuaCode(", tostring(text.source)\as_lua!)
+                lua = LuaCode\from(text.source, "LuaCode:from(", tostring(text.source)\as_lua!)
                 for bit in *text
                     if type(bit) == "string"
                         add_bit_lua(lua, bit\as_lua!)
@@ -88,11 +77,11 @@ compile = setmetatable({
                 return lua
             return operate_on_text code
 
-        ["lua >"]: (compile, tree, code)->
+        ["lua >"]: (compile, code)->
             if code.type != "Text"
-                return tree
+                return code
             operate_on_text = (text)->
-                lua = LuaCode(text.source)
+                lua = LuaCode\from(text.source)
                 for bit in *text
                     if type(bit) == "string"
                         lua\append bit
@@ -103,47 +92,53 @@ compile = setmetatable({
                 return lua
             return operate_on_text code
 
-        ["= lua"]: (compile, tree, code)-> compile.action["lua >"](compile, tree, code)
+        ["= lua"]: (compile, code)-> compile.action["lua >"](compile, code)
 
-        ["use"]: (compile, tree, path)->
+        ["use"]: (compile, path)->
             --if path.type == 'Text' and #path == 1 and type(path[1]) == 'string'
             --    unless import_to_1_from(compile, path[1])
             --        compile_error tree, "Could not find anything to import for #{path}"
-            return LuaCode(tree.source, "run_file_1_in(#{compile(path)}, _ENV)")
+            return LuaCode("run_file_1_in(#{compile(path)}, _ENV)")
 
-        ["tests"]: (compile, tree)-> LuaCode(tree.source, "TESTS")
-        ["test"]: (compile, tree, body)->
+        ["tests"]: (compile)-> LuaCode("TESTS")
+        ["test"]: (compile, body)->
             unless body.type == 'Block'
-                compile_error(tree, "This should be a Block")
+                compile_error(body, "This should be a Block")
             test_nomsu = body\get_source_code!\match(":[ ]*(.*)")
             if indent = test_nomsu\match("\n([ ]*)")
                 test_nomsu = test_nomsu\gsub("\n"..indent, "\n")
-            LuaCode tree.source, "TESTS[#{tostring(tree.source)\as_lua!}] = ", test_nomsu\as_lua!
+            return LuaCode "TESTS[#{tostring(body.source)\as_lua!}] = ", test_nomsu\as_lua!
 
-        ["is jit"]: (compile, tree, code)-> LuaCode(tree.source, "jit")
-        ["Lua version"]: (compile, tree, code)-> LuaCode(tree.source, "_VERSION")
-        ["nomsu environment"]: (compile, tree)-> LuaCode(tree.source, "_ENV")
+        ["is jit"]: (compile, code)-> LuaCode("jit")
+        ["Lua version"]: (compile, code)-> LuaCode("_VERSION")
+        ["nomsu environment"]: (compile)-> LuaCode("_ENV")
     }
 }, {
     __import: (other)=>
         import_to_1_from(@action, other.action)
         return
     __call: (compile, tree, force_value=false)->
-        if tree.version
-            if get_version = compile.action[("Nomsu version")\as_lua_id!]
-                if upgrade = compile.action[("1 upgraded from 2 to")\as_lua_id!]
-                    tree = upgrade(tree, tree.version, get_version!)
         switch tree.type
             when "Action"
                 stub = tree.stub
                 compile_action = compile.action[stub]
                 if not compile_action and math_expression\match(stub)
-                    compile_action = compile_math_expression
+                    lua = LuaCode\from(tree.source)
+                    for i,tok in ipairs tree
+                        if type(tok) == 'string'
+                            lua\append tok
+                        else
+                            tok_lua = compile(tok)
+                            tok_lua\parenthesize! if tok.type == "Action"
+                            lua\append tok_lua
+                        lua\append " " if i < #tree
+                    return lua
+
                 if compile_action and not tree.target
                     args = [arg for arg in *tree when type(arg) != "string"]
                     -- Force Lua to avoid tail call optimization for debugging purposes
                     -- TODO: use tail call?
-                    ret = compile_action(compile, tree, unpack(args))
+                    ret = compile_action(compile, unpack(args))
                     if ret == nil
                         info = debug.getinfo(compile_action, "S")
                         filename = Source\from_string(info.source).filename
@@ -151,11 +146,12 @@ compile = setmetatable({
                             "The compile-time action here (#{stub}) failed to return any value.",
                             "Look at the implementation of (#{stub}) in #{filename}:#{info.linedefined} and make sure it's returning something."
                     unless SyntaxTree\is_instance(ret)
+                        ret.source or= tree.source
                         return ret
                     if ret != tree
                         return compile(ret)
 
-                lua = LuaCode(tree.source)
+                lua = LuaCode\from(tree.source)
                 if tree.target -- Method call
                     target_lua = compile tree.target
                     target_text = target_lua\text!
@@ -174,7 +170,7 @@ compile = setmetatable({
                 return lua
 
             when "EscapedNomsu"
-                lua = LuaCode tree.source, "SyntaxTree{"
+                lua = LuaCode\from tree.source, "SyntaxTree{"
                 needs_comma, i = false, 1
                 as_lua = (x)->
                     if type(x) == 'number'
@@ -201,11 +197,11 @@ compile = setmetatable({
             
             when "Block"
                 if not force_value
-                    lua = LuaCode(tree.source)
+                    lua = LuaCode\from(tree.source)
                     lua\concat_append([compile(line) for line in *tree], "\n")
                     return lua
                 else
-                    lua = LuaCode(tree.source)
+                    lua = LuaCode\from(tree.source)
                     lua\append("((function()")
                     for i, line in ipairs(tree)
                         lua\append "\n    ", compile(line)
@@ -213,7 +209,7 @@ compile = setmetatable({
                     return lua
 
             when "Text"
-                lua = LuaCode(tree.source)
+                lua = LuaCode\from(tree.source)
                 string_buffer = ""
                 for i, bit in ipairs tree
                     if type(bit) == "string"
@@ -226,7 +222,7 @@ compile = setmetatable({
                     bit_lua = compile(bit)
                     if #lua.bits > 0 then lua\append ".."
                     if bit.type != "Text"
-                        bit_lua = LuaCode(bit.source, "tostring(",bit_lua,")")
+                        bit_lua = LuaCode\from(bit.source, "tostring(",bit_lua,")")
                     lua\append bit_lua
 
                 if string_buffer ~= "" or #lua.bits == 0
@@ -238,7 +234,7 @@ compile = setmetatable({
                 return lua
 
             when "List", "Dict"
-                lua = LuaCode tree.source, "#{tree.type}{"
+                lua = LuaCode\from tree.source, "#{tree.type}{"
                 i = 1
                 sep = ''
                 while i <= #tree
@@ -255,20 +251,26 @@ compile = setmetatable({
                         sep = ', '
                     i += 1
                 lua\append "}"
+                -- List/dict comprehenstion
                 if i <= #tree
-                    lua = LuaCode tree.source, "(function()\n    local it = ", lua
+                    lua = LuaCode\from tree.source, "(function()\n    local comprehension = ", lua
+                    if tree.type == "List"
+                        lua\append "\n    local function add(x) comprehension[#comprehension+1] = x end"
+                    else
+                        lua\append "\n    local function #{("add 1 =")\as_lua_id!}(k, v) comprehension[k] = v end"
                     while i <= #tree
                         lua\append "\n    "
                         if tree[i].type == 'Block' or tree[i].type == 'Comment'
                             lua\append compile(tree[i])
                         elseif tree[i].type == "DictEntry"
-                            lua\append "it[ ", compile(tree[i][1]), "] = ", (tree[i][2] and compile(tree[i][2]) or "true")
+                            entry_lua = compile(tree[i])
+                            lua\append (entry_lua\text!\sub(1,1) == '[' and "comprehension" or "comprehension."), entry_lua
                         else
-                            lua\append "it:add(", compile(tree[i]), ")"
+                            lua\append "comprehension[#comprehension+1] = ", compile(tree[i])
                         i += 1
-                    lua\append "\n    return it\nend)()"
+                    lua\append "\n    return comprehension\nend)()"
                 return lua
-                --lua = LuaCode tree.source, "#{tree.type}{"
+                --lua = LuaCode\from tree.source, "#{tree.type}{"
                 --lua\concat_append([compile(e) for e in *tree when e.type != 'Comment'], ", ", ",\n  ")
                 --lua\append "}"
                 --return lua
@@ -276,17 +278,17 @@ compile = setmetatable({
             when "DictEntry"
                 key, value = tree[1], tree[2]
                 key_lua = compile(key)
-                value_lua = value and compile(value) or LuaCode(key.source, "true")
+                value_lua = value and compile(value) or LuaCode\from(key.source, "true")
                 key_str = match(key_lua\text!, [=[^["']([a-zA-Z_][a-zA-Z0-9_]*)['"]$]=])
                 return if key_str and key_str\is_lua_id!
-                    LuaCode tree.source, key_str,"=",value_lua
+                    LuaCode\from tree.source, key_str,"=",value_lua
                 elseif sub(key_lua\text!,1,1) == "["
                     -- NOTE: this *must* use a space after the [ to avoid freaking out
                     -- Lua's parser if the inner expression is a long string. Lua
                     -- parses x[[[y]]] as x("[y]"), not as x["y"]
-                    LuaCode tree.source, "[ ",key_lua,"]=",value_lua
+                    LuaCode\from tree.source, "[ ",key_lua,"]=",value_lua
                 else
-                    LuaCode tree.source, "[",key_lua,"]=",value_lua
+                    LuaCode\from tree.source, "[",key_lua,"]=",value_lua
             
             when "IndexChain"
                 lua = compile(tree[1])
@@ -311,10 +313,10 @@ compile = setmetatable({
                 return lua
 
             when "Number"
-                return LuaCode(tree.source, tostring(tree[1]))
+                return LuaCode\from(tree.source, tostring(tree[1]))
 
             when "Var"
-                return LuaCode(tree.source, (tree[1])\as_lua_id!)
+                return LuaCode\from(tree.source, (tree[1])\as_lua_id!)
 
             when "FileChunks"
                 error("Can't convert FileChunks to a single block of lua, since each chunk's "..
@@ -322,7 +324,7 @@ compile = setmetatable({
             
             when "Comment"
                 -- TODO: implement?
-                return LuaCode(tree.source, "")
+                return LuaCode\from(tree.source, "")
             
             when "Error"
                 error("Can't compile errors")
diff --git a/nomsu_decompiler.lua b/nomsu_decompiler.lua
index 8d0aa7c..a3d7f41 100644
--- a/nomsu_decompiler.lua
+++ b/nomsu_decompiler.lua
@@ -47,7 +47,7 @@ local tree_to_inline_nomsu
 tree_to_inline_nomsu = function(tree)
   local _exp_0 = tree.type
   if "Action" == _exp_0 then
-    local nomsu = NomsuCode(tree.source)
+    local nomsu = NomsuCode:from(tree.source)
     if tree.target then
       local inline_target = tree_to_inline_nomsu(tree.target)
       if tree.target.type == "Action" then
@@ -88,9 +88,9 @@ tree_to_inline_nomsu = function(tree)
     if not (tree[1].type == "List" or tree[1].type == "Dict" or tree[1].type == "Var") then
       inner_nomsu:parenthesize()
     end
-    return NomsuCode(tree.source, "\\", inner_nomsu)
+    return NomsuCode:from(tree.source, "\\", inner_nomsu)
   elseif "Block" == _exp_0 then
-    local nomsu = NomsuCode(tree.source, ":")
+    local nomsu = NomsuCode:from(tree.source, ":")
     for i, line in ipairs(tree) do
       nomsu:append(i == 1 and " " or "; ")
       nomsu:append(tree_to_inline_nomsu(line))
@@ -119,11 +119,11 @@ tree_to_inline_nomsu = function(tree)
         end
       end
     end
-    local nomsu = NomsuCode(tree.source)
+    local nomsu = NomsuCode:from(tree.source)
     add_text(nomsu, tree)
-    return NomsuCode(tree.source, '"', nomsu, '"')
+    return NomsuCode:from(tree.source, '"', nomsu, '"')
   elseif "List" == _exp_0 or "Dict" == _exp_0 then
-    local nomsu = NomsuCode(tree.source, (tree.type == "List" and "[" or "{"))
+    local nomsu = NomsuCode:from(tree.source, (tree.type == "List" and "[" or "{"))
     for i, item in ipairs(tree) do
       if i > 1 then
         nomsu:append(", ")
@@ -136,7 +136,7 @@ tree_to_inline_nomsu = function(tree)
     local key, value = tree[1], tree[2]
     local nomsu
     if key.type == "Text" and #key == 1 and is_identifier(key[1]) then
-      nomsu = NomsuCode(key.source, key[1])
+      nomsu = NomsuCode:from(key.source, key[1])
     else
       nomsu = tree_to_inline_nomsu(key)
     end
@@ -154,7 +154,7 @@ tree_to_inline_nomsu = function(tree)
     end
     return nomsu
   elseif "IndexChain" == _exp_0 then
-    local nomsu = NomsuCode(tree.source)
+    local nomsu = NomsuCode:from(tree.source)
     for i, bit in ipairs(tree) do
       if i > 1 then
         nomsu:append(".")
@@ -173,9 +173,9 @@ tree_to_inline_nomsu = function(tree)
     end
     return nomsu
   elseif "Number" == _exp_0 then
-    return NomsuCode(tree.source, tostring(tree[1]))
+    return NomsuCode:from(tree.source, tostring(tree[1]))
   elseif "Var" == _exp_0 then
-    return NomsuCode(tree.source, "%", tree[1])
+    return NomsuCode:from(tree.source, "%", tree[1])
   elseif "FileChunks" == _exp_0 then
     return error("Can't inline a FileChunks")
   elseif "Comment" == _exp_0 then
@@ -188,7 +188,7 @@ tree_to_inline_nomsu = function(tree)
 end
 local tree_to_nomsu
 tree_to_nomsu = function(tree)
-  local nomsu = NomsuCode(tree.source)
+  local nomsu = NomsuCode:from(tree.source)
   local recurse
   recurse = function(t)
     local space = MAX_LINE - nomsu:trailing_line_len()
@@ -214,7 +214,7 @@ tree_to_nomsu = function(tree)
     local indented = tree_to_nomsu(t)
     if t.type == "Action" then
       if indented:is_multiline() then
-        return NomsuCode(t.source, "(..)\n    ", indented)
+        return NomsuCode:from(t.source, "(..)\n    ", indented)
       else
         indented:parenthesize()
       end
@@ -304,7 +304,7 @@ tree_to_nomsu = function(tree)
         nomsu:append(line_nomsu:match('\n[^\n]*\n') and "\n\n" or "\n")
       end
     end
-    return NomsuCode(tree.source, ":\n    ", nomsu)
+    return NomsuCode:from(tree.source, ":\n    ", nomsu)
   elseif "Text" == _exp_0 then
     local max_line = math.floor(1.25 * MAX_LINE)
     local add_text
@@ -357,7 +357,7 @@ tree_to_nomsu = function(tree)
       end
     end
     add_text(tree)
-    return NomsuCode(tree.source, '"\\\n    ..', nomsu, '"')
+    return NomsuCode:from(tree.source, '"\\\n    ..', nomsu, '"')
   elseif "List" == _exp_0 or "Dict" == _exp_0 then
     if #tree == 0 then
       nomsu:append(tree.type == "List" and "[]" or "{}")
@@ -376,14 +376,14 @@ tree_to_nomsu = function(tree)
       end
     end
     if tree.type == "List" then
-      return NomsuCode(tree.source, "[..]\n    ", nomsu)
+      return NomsuCode:from(tree.source, "[..]\n    ", nomsu)
     else
-      return NomsuCode(tree.source, "{..}\n    ", nomsu)
+      return NomsuCode:from(tree.source, "{..}\n    ", nomsu)
     end
   elseif "DictEntry" == _exp_0 then
     local key, value = tree[1], tree[2]
     if key.type == "Text" and #key == 1 and is_identifier(key[1]) then
-      nomsu = NomsuCode(key.source, key[1])
+      nomsu = NomsuCode:from(key.source, key[1])
     else
       nomsu = tree_to_inline_nomsu(key)
     end
diff --git a/nomsu_decompiler.moon b/nomsu_decompiler.moon
index df1c4d6..828df06 100644
--- a/nomsu_decompiler.moon
+++ b/nomsu_decompiler.moon
@@ -31,7 +31,7 @@ escape = (s)->
 tree_to_inline_nomsu = (tree)->
     switch tree.type
         when "Action"
-            nomsu = NomsuCode(tree.source)
+            nomsu = NomsuCode\from(tree.source)
             if tree.target
                 inline_target = tree_to_inline_nomsu(tree.target)
                 if tree.target.type == "Action"
@@ -61,10 +61,10 @@ tree_to_inline_nomsu = (tree)->
             inner_nomsu = tree_to_inline_nomsu(tree[1])
             unless tree[1].type == "List" or tree[1].type == "Dict" or tree[1].type == "Var"
                 inner_nomsu\parenthesize!
-            return NomsuCode(tree.source, "\\", inner_nomsu)
+            return NomsuCode\from(tree.source, "\\", inner_nomsu)
 
         when "Block"
-            nomsu = NomsuCode(tree.source, ":")
+            nomsu = NomsuCode\from(tree.source, ":")
             for i,line in ipairs tree
                 nomsu\append(i == 1 and " " or "; ")
                 nomsu\append tree_to_inline_nomsu(line)
@@ -86,12 +86,12 @@ tree_to_inline_nomsu = (tree)->
                         elseif bit.type == "Var" and type(tree[i+1]) == 'string' and not match(tree[i+1], "^[ \n\t,.:;#(){}[%]]")
                             interp_nomsu\parenthesize!
                         nomsu\append "\\", interp_nomsu
-            nomsu = NomsuCode(tree.source)
+            nomsu = NomsuCode\from(tree.source)
             add_text(nomsu, tree)
-            return NomsuCode(tree.source, '"', nomsu, '"')
+            return NomsuCode\from(tree.source, '"', nomsu, '"')
 
         when "List", "Dict"
-            nomsu = NomsuCode(tree.source, (tree.type == "List" and "[" or "{"))
+            nomsu = NomsuCode\from(tree.source, (tree.type == "List" and "[" or "{"))
             for i, item in ipairs tree
                 nomsu\append ", " if i > 1
                 nomsu\append tree_to_inline_nomsu(item)
@@ -101,7 +101,7 @@ tree_to_inline_nomsu = (tree)->
         when "DictEntry"
             key, value = tree[1], tree[2]
             nomsu = if key.type == "Text" and #key == 1 and is_identifier(key[1])
-                NomsuCode(key.source, key[1])
+                NomsuCode\from(key.source, key[1])
             else tree_to_inline_nomsu(key)
             nomsu\parenthesize! if key.type == "Action" or key.type == "Block"
             assert(value.type != "Block", "Didn't expect to find a Block as a value in a dict")
@@ -113,7 +113,7 @@ tree_to_inline_nomsu = (tree)->
             return nomsu
         
         when "IndexChain"
-            nomsu = NomsuCode(tree.source)
+            nomsu = NomsuCode\from(tree.source)
             for i, bit in ipairs tree
                 nomsu\append "." if i > 1
                 local bit_nomsu
@@ -127,10 +127,10 @@ tree_to_inline_nomsu = (tree)->
             return nomsu
         
         when "Number"
-            return NomsuCode(tree.source, tostring(tree[1]))
+            return NomsuCode\from(tree.source, tostring(tree[1]))
 
         when "Var"
-            return NomsuCode(tree.source, "%", tree[1])
+            return NomsuCode\from(tree.source, "%", tree[1])
 
         when "FileChunks"
             error("Can't inline a FileChunks")
@@ -146,7 +146,7 @@ tree_to_inline_nomsu = (tree)->
             error("Unknown type: #{tree.type}")
 
 tree_to_nomsu = (tree)->
-    nomsu = NomsuCode(tree.source)
+    nomsu = NomsuCode\from(tree.source)
 
     -- For concision:
     recurse = (t)->
@@ -166,7 +166,7 @@ tree_to_nomsu = (tree)->
         indented = tree_to_nomsu(t)
         if t.type == "Action"
             if indented\is_multiline!
-                return NomsuCode(t.source, "(..)\n    ", indented)
+                return NomsuCode\from(t.source, "(..)\n    ", indented)
             else indented\parenthesize!
         return indented
 
@@ -234,7 +234,7 @@ tree_to_nomsu = (tree)->
                 if i < #tree
                     -- number of lines > 2 (TODO: improve this)
                     nomsu\append(line_nomsu\match('\n[^\n]*\n') and "\n\n" or "\n")
-            return NomsuCode(tree.source, ":\n    ", nomsu)
+            return NomsuCode\from(tree.source, ":\n    ", nomsu)
 
         when "Text"
             -- Multi-line text has more generous wrap margins
@@ -274,7 +274,7 @@ tree_to_nomsu = (tree)->
                         if interp_nomsu\is_multiline!
                             nomsu\append "\n.."
             add_text(tree)
-            return NomsuCode(tree.source, '"\\\n    ..', nomsu, '"')
+            return NomsuCode\from(tree.source, '"\\\n    ..', nomsu, '"')
 
         when "List", "Dict"
             if #tree == 0
@@ -290,14 +290,14 @@ tree_to_nomsu = (tree)->
                 if i < #tree
                     nomsu\append((item_nomsu\is_multiline! or nomsu\trailing_line_len! + #tostring(item_nomsu) >= MAX_LINE) and '\n' or ', ')
             return if tree.type == "List" then
-                NomsuCode(tree.source, "[..]\n    ", nomsu)
+                NomsuCode\from(tree.source, "[..]\n    ", nomsu)
             else
-                NomsuCode(tree.source, "{..}\n    ", nomsu)
+                NomsuCode\from(tree.source, "{..}\n    ", nomsu)
         
         when "DictEntry"
             key, value = tree[1], tree[2]
             nomsu = if key.type == "Text" and #key == 1 and is_identifier(key[1])
-                NomsuCode(key.source, key[1])
+                NomsuCode\from(key.source, key[1])
             else tree_to_inline_nomsu(key)
             nomsu\parenthesize! if key.type == "Block"
             value_nomsu = tree_to_nomsu(value)
diff --git a/nomsu_environment.lua b/nomsu_environment.lua
index e72eb20..dd8b3ec 100644
--- a/nomsu_environment.lua
+++ b/nomsu_environment.lua
@@ -52,6 +52,7 @@ do
   tree_to_nomsu, tree_to_inline_nomsu = _obj_0.tree_to_nomsu, _obj_0.tree_to_inline_nomsu
 end
 local compile = require('nomsu_compiler')
+local _currently_running_files = List({ })
 local nomsu_environment = Importer({
   NOMSU_COMPILER_VERSION = 12,
   NOMSU_SYNTAX_VERSION = max_parser_version,
@@ -113,7 +114,7 @@ local nomsu_environment = Importer({
   _1_parsed = function(nomsu_code)
     if type(nomsu_code) == 'string' then
       local filename = Files.spoof(nomsu_code)
-      nomsu_code = NomsuCode(Source(filename, 1, #nomsu_code), nomsu_code)
+      nomsu_code = NomsuCode:from(Source(filename, 1, #nomsu_code), nomsu_code)
     end
     local source = nomsu_code.source
     nomsu_code = tostring(nomsu_code)
@@ -186,7 +187,7 @@ local nomsu_environment = Importer({
   run_1_in = function(to_run, environment)
     if type(to_run) == 'string' then
       local filename = Files.spoof(to_run)
-      to_run = NomsuCode(Source(filename, 1, #to_run), to_run)
+      to_run = NomsuCode:from(Source(filename, 1, #to_run), to_run)
       local ret = environment.run_1_in(to_run, environment)
       return ret
     elseif NomsuCode:is_instance(to_run) then
@@ -277,6 +278,14 @@ local nomsu_environment = Importer({
       import_to_1_from(environment, environment.FILE_CACHE[path])
       return 
     end
+    if _currently_running_files:has(path) then
+      local i = _currently_running_files:index_of(path)
+      _currently_running_files:add(path)
+      local circle = _currently_running_files:from_1_to(i, -1)
+      print(_currently_running_files, path)
+      error("Circular import detected:\n           " .. circle:joined_with("\n..imports  "))
+    end
+    _currently_running_files:add(path)
     local mod = _1_forked(environment)
     assert(mod._1_parsed)
     mod._ENV = mod
@@ -291,10 +300,10 @@ local nomsu_environment = Importer({
         local code
         if optimization ~= 0 and Files.read(lua_filename) then
           local file = Files.read(lua_filename)
-          code = LuaCode(Source(filename, 1, #file), file)
+          code = LuaCode:from(Source(filename, 1, #file), file)
         else
           local file = Files.read(filename)
-          code = NomsuCode(Source(filename, 1, #file), file)
+          code = NomsuCode:from(Source(filename, 1, #file), file)
         end
         environment.run_1_in(code, mod)
         _continue_0 = true
@@ -305,6 +314,7 @@ local nomsu_environment = Importer({
     end
     import_to_1_from(environment, mod)
     environment.FILE_CACHE[path] = mod
+    return _currently_running_files:remove()
   end,
   compile_error_at = function(tree, err_msg, hint)
     if hint == nil then
diff --git a/nomsu_environment.moon b/nomsu_environment.moon
index b216242..bfc5edc 100644
--- a/nomsu_environment.moon
+++ b/nomsu_environment.moon
@@ -32,6 +32,7 @@ for version=1,999
 
 {:tree_to_nomsu, :tree_to_inline_nomsu} = require "nomsu_decompiler"
 compile = require('nomsu_compiler')
+_currently_running_files = List{} -- Used to check for circular imports in run_file_1_in
 nomsu_environment = Importer{
     NOMSU_COMPILER_VERSION: 12, NOMSU_SYNTAX_VERSION: max_parser_version
     -- Lua stuff:
@@ -57,7 +58,7 @@ nomsu_environment = Importer{
     _1_parsed: (nomsu_code)->
         if type(nomsu_code) == 'string'
             filename = Files.spoof(nomsu_code)
-            nomsu_code = NomsuCode(Source(filename, 1, #nomsu_code), nomsu_code)
+            nomsu_code = NomsuCode\from(Source(filename, 1, #nomsu_code), nomsu_code)
         source = nomsu_code.source
         nomsu_code = tostring(nomsu_code)
         version = nomsu_code\match("^#![^\n]*nomsu[ ]+-V[ ]*([0-9.]+)")
@@ -88,7 +89,7 @@ nomsu_environment = Importer{
     run_1_in: (to_run, environment)->
         if type(to_run) == 'string'
             filename = Files.spoof(to_run)
-            to_run = NomsuCode(Source(filename, 1, #to_run), to_run)
+            to_run = NomsuCode\from(Source(filename, 1, #to_run), to_run)
             ret = environment.run_1_in(to_run, environment)
             return ret
         elseif NomsuCode\is_instance(to_run)
@@ -151,6 +152,13 @@ nomsu_environment = Importer{
         if environment.FILE_CACHE[path]
             import_to_1_from(environment, environment.FILE_CACHE[path])
             return
+        if _currently_running_files\has(path)
+            i = _currently_running_files\index_of(path)
+            _currently_running_files\add path
+            circle = _currently_running_files\from_1_to(i, -1)
+            print(_currently_running_files, path)
+            error("Circular import detected:\n           "..circle\joined_with("\n..imports  "))
+        _currently_running_files\add path
         mod = _1_forked(environment)
         assert mod._1_parsed
         mod._ENV = mod
@@ -160,13 +168,14 @@ nomsu_environment = Importer{
             -- TODO: don't automatically use precompiled version?
             code = if optimization != 0 and Files.read(lua_filename)
                 file = Files.read(lua_filename)
-                LuaCode(Source(filename, 1, #file), file)
+                LuaCode\from(Source(filename, 1, #file), file)
             else
                 file = Files.read(filename)
-                NomsuCode(Source(filename, 1, #file), file)
+                NomsuCode\from(Source(filename, 1, #file), file)
             environment.run_1_in(code, mod)
         import_to_1_from(environment, mod)
         environment.FILE_CACHE[path] = mod
+        _currently_running_files\remove!
 
     compile_error_at: (tree, err_msg, hint=nil)->
         err_str = pretty_error{