diff --git a/code_obj.lua b/code_obj.lua
index 990f3bc..2aba03d 100644
--- a/code_obj.lua
+++ b/code_obj.lua
@@ -12,6 +12,7 @@ Source = immutable({
 }, {
   name = "Source",
   __new = function(self, filename, start, stop)
+    assert(type(filename) == 'string')
     if not start then
       start, stop = 1, #FILE_CACHE[filename]
     end
@@ -159,7 +160,7 @@ do
       if type(self.source) == 'string' then
         self.source = Source:from_string(self.source)
       end
-      return assert(self.source)
+      return assert(self.source and Source:is_instance(self.source))
     end,
     __base = _base_0,
     __name = "Code"
diff --git a/code_obj.moon b/code_obj.moon
index e821b7e..17ec816 100644
--- a/code_obj.moon
+++ b/code_obj.moon
@@ -6,6 +6,7 @@ export LINE_STARTS
 Source = immutable {"filename","start","stop"}, {
     name:"Source"
     __new: (filename, start, stop)=>
+        assert(type(filename) == 'string')
         if not start
             start, stop = 1, #FILE_CACHE[filename]
         if stop and start > stop+1 then error("Invalid range: #{start}, #{stop}")
@@ -71,7 +72,7 @@ class Code
         @append(...)
         if type(@source) == 'string'
             @source = Source\from_string(@source)
-        assert(@source)
+        assert(@source and Source\is_instance(@source))
             
     append: (...)=>
         n = select("#",...)
diff --git a/core/text.nom b/core/text.nom
index 95451ee..8b75ca4 100644
--- a/core/text.nom
+++ b/core/text.nom
@@ -27,7 +27,7 @@ lua> ".."
         };
         for name, e in pairs(escapes) do
             local lua = "'"..e.."'";
-            nomsu:define_compile_action(name, function(tree) return Lua.Value(tree.value, lua); end);
+            nomsu:define_compile_action(name, function(tree) return Lua.Value(tree.source, lua); end);
         end
         local colors = {
             ["reset color"]="\\\\27[0m", bright="\\\\27[1m", dim="\\\\27[2m", underscore="\\\\27[4m",
@@ -42,9 +42,9 @@ lua> ".."
         for name, c in pairs(colors) do
             local color = "'"..c.."'";
             local reset = "'"..colors["reset color"].."'";
-            nomsu:define_compile_action(name, function(tree) return Lua.Value(tree.value, color); end);
+            nomsu:define_compile_action(name, function(tree) return Lua.Value(tree.source, color); end);
             nomsu:define_compile_action(name.." %", function(\%)
-                return Lua.Value(tree.value, color, "..", \(% as lua), "..", reset);
+                return Lua.Value(tree.source, color, "..", \(% as lua), "..", reset);
             end);
         end
     end
diff --git a/nomsu.lua b/nomsu.lua
index 10c907f..ddad7dd 100644
--- a/nomsu.lua
+++ b/nomsu.lua
@@ -233,7 +233,7 @@ setmetatable(NOMSU_DEFS, {
   __index = function(self, key)
     local make_node
     make_node = function(start, value, stop, userdata)
-      local source = userdata.source:sub(start, stop)
+      local source = userdata.source:sub(start, stop - 1)
       local tree
       if Types[key].is_multi then
         tree = Types[key](Tuple(unpack(value)), source)
@@ -313,6 +313,24 @@ do
     define_compile_action = function(self, signature, fn)
       return self:define_action(signature, fn, true)
     end,
+    lua_line_to_nomsu = function(self, source, line_no)
+      local pos = 0
+      local line = 0
+      local filename = source:match('"([^[]*)')
+      for line in FILE_CACHE[filename]:gmatch("[^\n]*\n") do
+        line = line + 1
+        pos = pos + #line
+        if line == line_no then
+          break
+        end
+      end
+      for i, entry in ipairs(self.source_map[source]) do
+        if entry[1] > pos then
+          return self.source_map[source][i - 1][2]
+        end
+      end
+      return self.source_map[source][#self.source_map[source]][2]
+    end,
     parse = function(self, nomsu_code)
       if type(nomsu_code) == 'string' then
         _nomsu_chunk_counter = _nomsu_chunk_counter + 1
@@ -419,7 +437,7 @@ do
             if not file then
               error("File does not exist: " .. tostring(filename), 0)
             end
-            ret = self:run(Nomsu(Source(filename), file), compile_fn)
+            ret = self:run(Nomsu(Source(filename, 1, #file), file), compile_fn)
           else
             error("Invalid filetype for " .. tostring(filename), 0)
           end
@@ -437,7 +455,7 @@ do
     run_lua = function(self, lua)
       assert(type(lua) ~= 'string', "Attempt to run lua string instead of Lua (object)")
       local lua_string = tostring(lua)
-      local run_lua_fn, err = load(lua_string, filename, "t", self.environment)
+      local run_lua_fn, err = load(lua_string, tostring(lua.source), "t", self.environment)
       if not run_lua_fn then
         local n = 1
         local fn
@@ -448,6 +466,69 @@ do
         local line_numbered_lua = "1  |" .. lua_string:gsub("\n", fn)
         error("Failed to compile generated code:\n" .. tostring(colored.bright(colored.blue(colored.onblack(line_numbered_lua)))) .. "\n\n" .. tostring(err), 0)
       end
+      if not (self.source_map[tostring(lua.source)]) then
+        local map = { }
+        local offset = 1
+        local source = lua.source
+        local nomsu_raw = FILE_CACHE[source.filename]:sub(source.start, source.stop)
+        local get_line_starts
+        get_line_starts = function(s)
+          local starts = { }
+          local pos = 1
+          for line in s:gmatch("[^\n]*\n") do
+            insert(starts, pos)
+            pos = pos + #line
+          end
+          insert(starts, pos)
+          return starts
+        end
+        local nomsu_line_to_pos = get_line_starts(nomsu_raw)
+        local lua_line_to_pos = get_line_starts(tostring(lua))
+        local pos_to_line
+        pos_to_line = function(line_starts, pos)
+          local lo, hi = 1, #line_starts
+          while lo <= hi do
+            local mid = math.floor((lo + hi) / 2)
+            if line_starts[mid] > pos then
+              hi = mid - 1
+            else
+              lo = mid + 1
+            end
+          end
+          return hi
+        end
+        local lua_line = 1
+        local nomsu_line = pos_to_line(nomsu_line_to_pos, lua.source.start)
+        local fn
+        fn = function(s)
+          if type(s) == 'string' then
+            map[lua_line] = map[lua_line] or {
+              nomsu_line
+            }
+            for nl in s:gmatch("\n") do
+              lua_line = lua_line + 1
+              map[lua_line] = map[lua_line] or {
+                nomsu_line
+              }
+            end
+          else
+            local old_line = nomsu_line
+            if s.source then
+              nomsu_line = pos_to_line(nomsu_line_to_pos, s.source.start)
+              if nomsu_line ~= old_line then
+                insert(map[lua_line], nomsu_line)
+              end
+            end
+            local _list_0 = s.bits
+            for _index_0 = 1, #_list_0 do
+              local b = _list_0[_index_0]
+              fn(b)
+            end
+          end
+        end
+        fn(lua)
+        self.source_map[tostring(lua.source)] = map
+      end
       return run_lua_fn()
     end,
     tree_to_lua = function(self, tree)
@@ -1185,6 +1266,7 @@ do
       self.file_metadata = setmetatable({ }, {
         __mode = "k"
       })
+      self.source_map = { }
       self.environment = {
         nomsu = self,
         repr = repr,
@@ -1407,6 +1489,27 @@ OPTIONS
           break
         end
       end
+      do
+        local map = nomsu.source_map[info.source]
+        if map then
+          if info.currentline then
+            info.currentline = (map[info.currentline] or {
+              info.currentline
+            })[1]
+          end
+          if info.linedefined then
+            info.linedefined = (map[info.linedefined] or {
+              info.linedefined
+            })[1]
+          end
+          if info.lastlinedefined then
+            info.lastlinedefined = (map[info.lastlinedefined] or {
+              info.lastlinedefined
+            })[1]
+          end
+          info.short_src = info.source:match('"([^[]*)')
+        end
+      end
       local _ = [=[            if metadata = nomsu.action_metadata[info.func]
                 info.name = metadata.aliases[1]
                 filename = if type(metadata.source) == 'string'
diff --git a/nomsu.moon b/nomsu.moon
index 883b702..36911bd 100755
--- a/nomsu.moon
+++ b/nomsu.moon
@@ -202,7 +202,7 @@ NOMSU_DEFS = with {}
 
 setmetatable(NOMSU_DEFS, {__index:(key)=>
     make_node = (start, value, stop, userdata)->
-        source = userdata.source\sub(start, stop)
+        source = userdata.source\sub(start, stop-1)
         tree = if Types[key].is_multi
             Types[key](Tuple(unpack(value)), source)
         else Types[key](value, source)
@@ -242,6 +242,7 @@ class NomsuCompiler
                 return id
         })
         @file_metadata = setmetatable({}, {__mode:"k"})
+        @source_map = {}
 
         @environment = {
             -- Discretionary/convenience stuff
@@ -324,6 +325,20 @@ class NomsuCompiler
     define_compile_action: (signature, fn)=>
         return @define_action(signature, fn, true)
 
+    lua_line_to_nomsu: (source, line_no)=>
+        pos = 0
+        line = 0
+        filename = source\match('"([^[]*)')
+        for line in FILE_CACHE[filename]\gmatch("[^\n]*\n")
+            line += 1
+            pos += #line
+            if line == line_no
+                break
+        for i, entry in ipairs @source_map[source]
+            if entry[1] > pos
+                return @source_map[source][i-1][2]
+        return @source_map[source][#@source_map[source]][2]
+
     _nomsu_chunk_counter = 0
     parse: (nomsu_code)=>
         if type(nomsu_code) == 'string'
@@ -393,7 +408,7 @@ class NomsuCompiler
                 file = file or FILE_CACHE[filename]
                 if not file
                     error("File does not exist: #{filename}", 0)
-                ret = @run(Nomsu(Source(filename), file), compile_fn)
+                ret = @run(Nomsu(Source(filename,1,#file), file), compile_fn)
             else
                 error("Invalid filetype for #{filename}", 0)
             loaded[filename] = ret or true
@@ -405,7 +420,7 @@ class NomsuCompiler
     run_lua: (lua)=>
         assert(type(lua) != 'string', "Attempt to run lua string instead of Lua (object)")
         lua_string = tostring(lua)
-        run_lua_fn, err = load(lua_string, filename, "t", @environment)
+        run_lua_fn, err = load(lua_string, tostring(lua.source), "t", @environment)
         if not run_lua_fn
             n = 1
             fn = ->
@@ -413,6 +428,53 @@ class NomsuCompiler
                 ("\n%-3d|")\format(n)
             line_numbered_lua = "1  |"..lua_string\gsub("\n", fn)
             error("Failed to compile generated code:\n#{colored.bright colored.blue colored.onblack line_numbered_lua}\n\n#{err}", 0)
+        unless @source_map[tostring(lua.source)]
+            map = {}
+            offset = 1
+            source = lua.source
+            nomsu_raw = FILE_CACHE[source.filename]\sub(source.start, source.stop)
+
+            get_line_starts = (s)->
+                starts = {}
+                pos = 1
+                for line in s\gmatch("[^\n]*\n")
+                    insert starts, pos
+                    pos += #line
+                insert starts, pos
+                return starts
+
+            nomsu_line_to_pos = get_line_starts(nomsu_raw)
+            lua_line_to_pos = get_line_starts(tostring(lua))
+
+            pos_to_line = (line_starts, pos)->
+                -- Binary search for line number of position
+                lo, hi = 1, #line_starts
+                while lo <= hi
+                    mid = math.floor((lo+hi)/2)
+                    if line_starts[mid] > pos
+                        hi = mid-1
+                    else lo = mid+1
+                return hi
+
+            lua_line = 1
+            nomsu_line = pos_to_line(nomsu_line_to_pos, lua.source.start)
+            fn = (s)->
+                if type(s) == 'string'
+                    map[lua_line] or= {nomsu_line}
+                    for nl in s\gmatch("\n")
+                        lua_line += 1
+                        map[lua_line] or= {nomsu_line}
+                else
+                    old_line = nomsu_line
+                    if s.source
+                        nomsu_line = pos_to_line(nomsu_line_to_pos, s.source.start)
+                        if nomsu_line != old_line
+                            insert map[lua_line], nomsu_line
+                    for b in *s.bits do fn(b)
+            fn(lua)
+            -- Mapping from lua line number to nomsu line numbers
+            @source_map[tostring(lua.source)] = map
+
         return run_lua_fn!
 
     MAX_LINE = 80 -- For beautification purposes, try not to make lines much longer than this value
@@ -993,6 +1055,15 @@ OPTIONS
                 if v == info.func
                     info.name = k
                     break
+
+            if map = nomsu.source_map[info.source]
+                if info.currentline
+                    info.currentline = (map[info.currentline] or {info.currentline})[1]
+                if info.linedefined
+                    info.linedefined = (map[info.linedefined] or {info.linedefined})[1]
+                if info.lastlinedefined
+                    info.lastlinedefined = (map[info.lastlinedefined] or {info.lastlinedefined})[1]
+                info.short_src = info.source\match('"([^[]*)')
             [=[
             if metadata = nomsu.action_metadata[info.func]
                 info.name = metadata.aliases[1]