refactor(treesitter): simplify argument checks for userdata

src/nvim/lua/treesitter.c

@@ -258,14 +258,19 @@ int tslua_remove_lang(lua_State *L)
   return 1;
 }
 
-int tslua_inspect_lang(lua_State *L)
+static TSLanguage *lang_check(lua_State *L, int index)
 {
-  const char *lang_name = luaL_checkstring(L, 1);
+  const char *lang_name = luaL_checkstring(L, index);
-
   TSLanguage *lang = pmap_get(cstr_t)(&langs, lang_name);
   if (!lang) {
-    return luaL_error(L, "no such language: %s", lang_name);
+    luaL_error(L, "no such language: %s", lang_name);
   }
+  return lang;
+}
+
+int tslua_inspect_lang(lua_State *L)
+{
+  TSLanguage *lang = lang_check(L, 1);
 
   lua_createtable(L, 0, 2);  // [retval]
 
@@ -308,19 +313,14 @@ int tslua_inspect_lang(lua_State *L)
 
 int tslua_push_parser(lua_State *L)
 {
-  // Gather language name
+  TSLanguage *lang = lang_check(L, 1);
-  const char *lang_name = luaL_checkstring(L, 1);
-
-  TSLanguage *lang = pmap_get(cstr_t)(&langs, lang_name);
-  if (!lang) {
-    return luaL_error(L, "no such language: %s", lang_name);
-  }
 
   TSParser **parser = lua_newuserdata(L, sizeof(TSParser *));
   *parser = ts_parser_new();
 
   if (!ts_parser_set_language(*parser, lang)) {
     ts_parser_delete(*parser);
+    const char *lang_name = luaL_checkstring(L, 1);
     return luaL_error(L, "Failed to load language : %s", lang_name);
   }
 
@@ -329,9 +329,13 @@ int tslua_push_parser(lua_State *L)
   return 1;
 }
 
-static TSParser **parser_check(lua_State *L, uint16_t index)
+static TSParser *parser_check(lua_State *L, uint16_t index)
 {
-  return luaL_checkudata(L, index, TS_META_PARSER);
+  TSParser **ud = luaL_checkudata(L, index, TS_META_PARSER);
+  if (!ud || !(*ud)) {
+    luaL_argerror(L, index, "TSParser expected");
+  }
+  return *ud;
 }
 
 static void logger_gc(TSLogger logger)
@@ -347,13 +351,9 @@ static void logger_gc(TSLogger logger)
 
 static int parser_gc(lua_State *L)
 {
-  TSParser **p = parser_check(L, 1);
+  TSParser *p = parser_check(L, 1);
-  if (!p) {
+  logger_gc(ts_parser_logger(p));
-    return 0;
+  ts_parser_delete(p);
-  }
-
-  logger_gc(ts_parser_logger(*p));
-  ts_parser_delete(*p);
   return 0;
 }
 
@@ -426,11 +426,7 @@ static void push_ranges(lua_State *L, const TSRange *ranges, const size_t length
 
 static int parser_parse(lua_State *L)
 {
-  TSParser **p = parser_check(L, 1);
+  TSParser *p = parser_check(L, 1);
-  if (!p || !(*p)) {
-    return 0;
-  }
-
   TSTree *old_tree = NULL;
   if (!lua_isnil(L, 2)) {
     TSLuaTree *ud = tree_check(L, 2);
@@ -449,7 +445,7 @@ static int parser_parse(lua_State *L)
   switch (lua_type(L, 3)) {
   case LUA_TSTRING:
     str = lua_tolstring(L, 3, &len);
-    new_tree = ts_parser_parse_string(*p, old_tree, str, (uint32_t)len);
+    new_tree = ts_parser_parse_string(p, old_tree, str, (uint32_t)len);
     break;
 
   case LUA_TNUMBER:
@@ -465,7 +461,7 @@ static int parser_parse(lua_State *L)
     }
 
     input = (TSInput){ (void *)buf, input_cb, TSInputEncodingUTF8 };
-    new_tree = ts_parser_parse(*p, old_tree, input);
+    new_tree = ts_parser_parse(p, old_tree, input);
 
     break;
 
@@ -496,21 +492,14 @@ static int parser_parse(lua_State *L)
 
 static int parser_reset(lua_State *L)
 {
-  TSParser **p = parser_check(L, 1);
+  TSParser *p = parser_check(L, 1);
-  if (p && *p) {
+  ts_parser_reset(p);
-    ts_parser_reset(*p);
-  }
-
   return 0;
 }
 
 static int tree_copy(lua_State *L)
 {
   TSLuaTree *ud = tree_check(L, 1);
-  if (!ud) {
-    return 0;
-  }
-
   TSTree *copy = ts_tree_copy(ud->tree);
   push_tree(L, copy);  // [tree]
 
@@ -525,9 +514,6 @@ static int tree_edit(lua_State *L)
   }
 
   TSLuaTree *ud = tree_check(L, 1);
-  if (!ud) {
-    return 0;
-  }
 
   uint32_t start_byte = (uint32_t)luaL_checkint(L, 2);
   uint32_t old_end_byte = (uint32_t)luaL_checkint(L, 3);
@@ -547,9 +533,6 @@ static int tree_edit(lua_State *L)
 static int tree_get_ranges(lua_State *L)
 {
   TSLuaTree *ud = tree_check(L, 1);
-  if (!ud) {
-    return 0;
-  }
 
   bool include_bytes = (lua_gettop(L) >= 2) && lua_toboolean(L, 2);
 
@@ -562,6 +545,11 @@ static int tree_get_ranges(lua_State *L)
   return 1;
 }
 
+static void range_err(lua_State *L)
+{
+  luaL_error(L, "Ranges can only be made from 6 element long tables or nodes.");
+}
+
 // Use the top of the stack (without popping it) to create a TSRange, it can be
 // either a lua table or a TSNode
 static void range_from_lua(lua_State *L, TSRange *range)
@@ -571,7 +559,7 @@ static void range_from_lua(lua_State *L, TSRange *range)
   if (lua_istable(L, -1)) {
     // should be a table of 6 elements
     if (lua_objlen(L, -1) != 6) {
-      goto error;
+      range_err(L);
     }
 
     lua_rawgeti(L, -1, 1);  // [ range, start_row]
@@ -610,7 +598,7 @@ static void range_from_lua(lua_State *L, TSRange *range)
       .start_byte = start_byte,
       .end_byte = end_byte,
     };
-  } else if (node_check(L, -1, &node)) {
+  } else if (node_check2(L, -1, &node)) {
     *range = (TSRange) {
       .start_point = ts_node_start_point(node),
       .end_point = ts_node_end_point(node),
@@ -618,29 +606,20 @@ static void range_from_lua(lua_State *L, TSRange *range)
       .end_byte = ts_node_end_byte(node)
     };
   } else {
-    goto error;
+    range_err(L);
   }
-  return;
-error:
-  luaL_error(L,
-             "Ranges can only be made from 6 element long tables or nodes.");
 }
 
 static int parser_set_ranges(lua_State *L)
 {
   if (lua_gettop(L) < 2) {
-    return luaL_error(L,
+    return luaL_error(L, "not enough args to parser:set_included_ranges()");
-                      "not enough args to parser:set_included_ranges()");
   }
 
-  TSParser **p = parser_check(L, 1);
+  TSParser *p = parser_check(L, 1);
-  if (!p) {
-    return 0;
-  }
 
   if (!lua_istable(L, 2)) {
-    return luaL_error(L,
+    return luaL_argerror(L, 2, "table expected.");
-                      "argument for parser:set_included_ranges() should be a table.");
   }
 
   size_t tbl_len = lua_objlen(L, 2);
@@ -654,7 +633,7 @@ static int parser_set_ranges(lua_State *L)
   }
 
   // This memcpies ranges, thus we can free it afterwards
-  ts_parser_set_included_ranges(*p, ranges, (uint32_t)tbl_len);
+  ts_parser_set_included_ranges(p, ranges, (uint32_t)tbl_len);
   xfree(ranges);
 
   return 0;
@@ -662,15 +641,12 @@ static int parser_set_ranges(lua_State *L)
 
 static int parser_get_ranges(lua_State *L)
 {
-  TSParser **p = parser_check(L, 1);
+  TSParser *p = parser_check(L, 1);
-  if (!p) {
-    return 0;
-  }
 
   bool include_bytes = (lua_gettop(L) >= 2) && lua_toboolean(L, 2);
 
   uint32_t len;
-  const TSRange *ranges = ts_parser_included_ranges(*p, &len);
+  const TSRange *ranges = ts_parser_included_ranges(p, &len);
 
   push_ranges(L, ranges, len, include_bytes);
   return 1;
@@ -678,28 +654,21 @@ static int parser_get_ranges(lua_State *L)
 
 static int parser_set_timeout(lua_State *L)
 {
-  TSParser **p = parser_check(L, 1);
+  TSParser *p = parser_check(L, 1);
-  if (!p) {
-    return 0;
-  }
 
   if (lua_gettop(L) < 2) {
     luaL_error(L, "integer expected");
   }
 
   uint32_t timeout = (uint32_t)luaL_checkinteger(L, 2);
-  ts_parser_set_timeout_micros(*p, timeout);
+  ts_parser_set_timeout_micros(p, timeout);
   return 0;
 }
 
 static int parser_get_timeout(lua_State *L)
 {
-  TSParser **p = parser_check(L, 1);
+  TSParser *p = parser_check(L, 1);
-  if (!p) {
+  lua_pushinteger(L, (lua_Integer)ts_parser_timeout_micros(p));
-    return 0;
-  }
-
-  lua_pushinteger(L, (lua_Integer)ts_parser_timeout_micros(*p));
   return 1;
 }
 
@@ -723,10 +692,7 @@ static void logger_cb(void *payload, TSLogType logtype, const char *s)
 
 static int parser_set_logger(lua_State *L)
 {
-  TSParser **p = parser_check(L, 1);
+  TSParser *p = parser_check(L, 1);
-  if (!p) {
-    return 0;
-  }
 
   if (!lua_isboolean(L, 2)) {
     return luaL_argerror(L, 2, "boolean expected");
@@ -756,18 +722,14 @@ static int parser_set_logger(lua_State *L)
     .log = logger_cb
   };
 
-  ts_parser_set_logger(*p, logger);
+  ts_parser_set_logger(p, logger);
   return 0;
 }
 
 static int parser_get_logger(lua_State *L)
 {
-  TSParser **p = parser_check(L, 1);
+  TSParser *p = parser_check(L, 1);
-  if (!p) {
+  TSLogger logger = ts_parser_logger(p);
-    return 0;
-  }
-
-  TSLogger logger = ts_parser_logger(*p);
   if (logger.log) {
     TSLuaLoggerOpts *opts = (TSLuaLoggerOpts *)logger.payload;
     lua_rawgeti(L, LUA_REGISTRYINDEX, opts->cb);
@@ -811,15 +773,16 @@ static void push_tree(lua_State *L, TSTree *tree)
 static TSLuaTree *tree_check(lua_State *L, int index)
 {
   TSLuaTree *ud = luaL_checkudata(L, index, TS_META_TREE);
+  if (!ud) {
+    luaL_argerror(L, index, "TSTree expected");
+  }
   return ud;
 }
 
 static int tree_gc(lua_State *L)
 {
   TSLuaTree *ud = tree_check(L, 1);
-  if (ud) {
+  ts_tree_delete(ud->tree);
-    ts_tree_delete(ud->tree);
-  }
   return 0;
 }
 
@@ -832,9 +795,6 @@ static int tree_tostring(lua_State *L)
 static int tree_root(lua_State *L)
 {
   TSLuaTree *ud = tree_check(L, 1);
-  if (!ud) {
-    return 0;
-  }
   TSNode root = ts_tree_root_node(ud->tree);
   push_node(L, root, 1);
   return 1;
@@ -864,7 +824,7 @@ static void push_node(lua_State *L, TSNode node, int uindex)
   lua_setfenv(L, -2);  // [udata]
 }
 
-static bool node_check(lua_State *L, int index, TSNode *res)
+static bool node_check2(lua_State *L, int index, TSNode *res)
 {
   TSNode *ud = luaL_checkudata(L, index, TS_META_NODE);
   if (ud) {
@@ -874,12 +834,18 @@ static bool node_check(lua_State *L, int index, TSNode *res)
   return false;
 }
 
+static TSNode node_check(lua_State *L, int index)
+{
+  TSNode *ud = luaL_checkudata(L, index, TS_META_NODE);
+  if (!ud) {
+    luaL_argerror(L, index, "TSNode expected");
+  }
+  return *ud;
+}
+
 static int node_tostring(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   lua_pushstring(L, "<node ");
   lua_pushstring(L, ts_node_type(node));
   lua_pushstring(L, ">");
@@ -889,37 +855,22 @@ static int node_tostring(lua_State *L)
 
 static int node_eq(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
+  TSNode node2 = node_check(L, 2);
-    return 0;
-  }
-
-  TSNode node2;
-  if (!node_check(L, 2, &node2)) {
-    return 0;
-  }
-
   lua_pushboolean(L, ts_node_eq(node, node2));
   return 1;
 }
 
 static int node_id(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
-
   lua_pushlstring(L, (const char *)&node.id, sizeof node.id);
   return 1;
 }
 
 static int node_range(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
 
   bool include_bytes = (lua_gettop(L) >= 2) && lua_toboolean(L, 2);
 
@@ -945,10 +896,7 @@ static int node_range(lua_State *L)
 
 static int node_start(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSPoint start = ts_node_start_point(node);
   uint32_t start_byte = ts_node_start_byte(node);
   lua_pushinteger(L, start.row);
@@ -959,10 +907,7 @@ static int node_start(lua_State *L)
 
 static int node_end(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSPoint end = ts_node_end_point(node);
   uint32_t end_byte = ts_node_end_byte(node);
   lua_pushinteger(L, end.row);
@@ -973,10 +918,7 @@ static int node_end(lua_State *L)
 
 static int node_child_count(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   uint32_t count = ts_node_child_count(node);
   lua_pushinteger(L, count);
   return 1;
@@ -984,10 +926,7 @@ static int node_child_count(lua_State *L)
 
 static int node_named_child_count(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   uint32_t count = ts_node_named_child_count(node);
   lua_pushinteger(L, count);
   return 1;
@@ -995,20 +934,14 @@ static int node_named_child_count(lua_State *L)
 
 static int node_type(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   lua_pushstring(L, ts_node_type(node));
   return 1;
 }
 
 static int node_symbol(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSSymbol symbol = ts_node_symbol(node);
   lua_pushinteger(L, symbol);
   return 1;
@@ -1016,10 +949,7 @@ static int node_symbol(lua_State *L)
 
 static int node_field(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
 
   size_t name_len;
   const char *field_name = luaL_checklstring(L, 2, &name_len);
@@ -1046,20 +976,14 @@ static int node_field(lua_State *L)
 
 static int node_named(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   lua_pushboolean(L, ts_node_is_named(node));
   return 1;
 }
 
 static int node_sexpr(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   char *allocated = ts_node_string(node);
   lua_pushstring(L, allocated);
   xfree(allocated);
@@ -1068,50 +992,35 @@ static int node_sexpr(lua_State *L)
 
 static int node_missing(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   lua_pushboolean(L, ts_node_is_missing(node));
   return 1;
 }
 
 static int node_extra(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   lua_pushboolean(L, ts_node_is_extra(node));
   return 1;
 }
 
 static int node_has_changes(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   lua_pushboolean(L, ts_node_has_changes(node));
   return 1;
 }
 
 static int node_has_error(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   lua_pushboolean(L, ts_node_has_error(node));
   return 1;
 }
 
 static int node_child(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   uint32_t num = (uint32_t)lua_tointeger(L, 2);
   TSNode child = ts_node_child(node, num);
 
@@ -1121,10 +1030,7 @@ static int node_child(lua_State *L)
 
 static int node_named_child(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   uint32_t num = (uint32_t)lua_tointeger(L, 2);
   TSNode child = ts_node_named_child(node, num);
 
@@ -1134,10 +1040,7 @@ static int node_named_child(lua_State *L)
 
 static int node_descendant_for_range(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSPoint start = { (uint32_t)lua_tointeger(L, 2),
                     (uint32_t)lua_tointeger(L, 3) };
   TSPoint end = { (uint32_t)lua_tointeger(L, 4),
@@ -1150,10 +1053,7 @@ static int node_descendant_for_range(lua_State *L)
 
 static int node_named_descendant_for_range(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSPoint start = { (uint32_t)lua_tointeger(L, 2),
                     (uint32_t)lua_tointeger(L, 3) };
   TSPoint end = { (uint32_t)lua_tointeger(L, 4),
@@ -1164,56 +1064,54 @@ static int node_named_descendant_for_range(lua_State *L)
   return 1;
 }
 
-static int node_next_child(lua_State *L)
+static TSTreeCursor *treecursor_check(lua_State *L, int index)
 {
   TSTreeCursor *ud = luaL_checkudata(L, lua_upvalueindex(1), TS_META_TREECURSOR);
   if (!ud) {
-    return 0;
+    luaL_error(L, "TSTreeCursor expected");
   }
+  return ud;
+}
 
-  TSNode source;
+static int node_next_child(lua_State *L)
-  if (!node_check(L, lua_upvalueindex(2), &source)) {
+{
-    return 0;
+  TSTreeCursor *cursor = treecursor_check(L, lua_upvalueindex(1));
-  }
+  TSNode source = node_check(L, lua_upvalueindex(2));
 
   // First call should return first child
-  if (ts_node_eq(source, ts_tree_cursor_current_node(ud))) {
+  if (ts_node_eq(source, ts_tree_cursor_current_node(cursor))) {
-    if (ts_tree_cursor_goto_first_child(ud)) {
+    if (ts_tree_cursor_goto_first_child(cursor)) {
       goto push;
     } else {
-      goto end;
+      return 0;
     }
   }
 
-  if (ts_tree_cursor_goto_next_sibling(ud)) {
+  if (ts_tree_cursor_goto_next_sibling(cursor)) {
 push:
     push_node(L,
-              ts_tree_cursor_current_node(ud),
+              ts_tree_cursor_current_node(cursor),
               lua_upvalueindex(2));  // [node]
 
-    const char *field = ts_tree_cursor_current_field_name(ud);
+    const char *field = ts_tree_cursor_current_field_name(cursor);
 
     if (field != NULL) {
-      lua_pushstring(L, ts_tree_cursor_current_field_name(ud));
+      lua_pushstring(L, ts_tree_cursor_current_field_name(cursor));
     } else {
       lua_pushnil(L);
     }  // [node, field_name_or_nil]
     return 2;
   }
 
-end:
   return 0;
 }
 
 static int node_iter_children(lua_State *L)
 {
-  TSNode source;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &source)) {
-    return 0;
-  }
 
   TSTreeCursor *ud = lua_newuserdata(L, sizeof(TSTreeCursor));  // [udata]
-  *ud = ts_tree_cursor_new(source);
+  *ud = ts_tree_cursor_new(node);
 
   lua_getfield(L, LUA_REGISTRYINDEX, TS_META_TREECURSOR);  // [udata, mt]
   lua_setmetatable(L, -2);  // [udata]
@@ -1225,17 +1123,14 @@ static int node_iter_children(lua_State *L)
 
 static int treecursor_gc(lua_State *L)
 {
-  TSTreeCursor *ud = luaL_checkudata(L, 1, TS_META_TREECURSOR);
+  TSTreeCursor *cursor = treecursor_check(L, 1);
-  ts_tree_cursor_delete(ud);
+  ts_tree_cursor_delete(cursor);
   return 0;
 }
 
 static int node_parent(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSNode parent = ts_node_parent(node);
   push_node(L, parent, 1);
   return 1;
@@ -1243,10 +1138,7 @@ static int node_parent(lua_State *L)
 
 static int node_next_sibling(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSNode sibling = ts_node_next_sibling(node);
   push_node(L, sibling, 1);
   return 1;
@@ -1254,10 +1146,7 @@ static int node_next_sibling(lua_State *L)
 
 static int node_prev_sibling(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSNode sibling = ts_node_prev_sibling(node);
   push_node(L, sibling, 1);
   return 1;
@@ -1265,10 +1154,7 @@ static int node_prev_sibling(lua_State *L)
 
 static int node_next_named_sibling(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSNode sibling = ts_node_next_named_sibling(node);
   push_node(L, sibling, 1);
   return 1;
@@ -1276,10 +1162,7 @@ static int node_next_named_sibling(lua_State *L)
 
 static int node_prev_named_sibling(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
   TSNode sibling = ts_node_prev_named_sibling(node);
   push_node(L, sibling, 1);
   return 1;
@@ -1287,10 +1170,7 @@ static int node_prev_named_sibling(lua_State *L)
 
 static int node_named_children(lua_State *L)
 {
-  TSNode source;
+  TSNode source = node_check(L, 1);
-  if (!node_check(L, 1, &source)) {
-    return 0;
-  }
   TSTreeCursor cursor = ts_tree_cursor_new(source);
 
   lua_newtable(L);
@@ -1312,11 +1192,7 @@ static int node_named_children(lua_State *L)
 
 static int node_root(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
-
   TSNode root = ts_tree_root_node(node.tree);
   push_node(L, root, 1);
   return 1;
@@ -1324,59 +1200,34 @@ static int node_root(lua_State *L)
 
 static int node_tree(lua_State *L)
 {
-  TSNode node;
+  node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
-
   lua_getfenv(L, 1);  // [udata, reftable]
   lua_rawgeti(L, -1, 1);  // [udata, reftable, tree_udata]
-
   return 1;
 }
 
 static int node_byte_length(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return 0;
-  }
-
   uint32_t start_byte = ts_node_start_byte(node);
   uint32_t end_byte = ts_node_end_byte(node);
-
   lua_pushinteger(L, end_byte - start_byte);
   return 1;
 }
 
 static int node_equal(lua_State *L)
 {
-  TSNode node1;
+  TSNode node1 = node_check(L, 1);
-  if (!node_check(L, 1, &node1)) {
+  TSNode node2 = node_check(L, 2);
-    return 0;
-  }
-
-  TSNode node2;
-  if (!node_check(L, 2, &node2)) {
-    return luaL_error(L, "TSNode expected");
-  }
-
   lua_pushboolean(L, ts_node_eq(node1, node2));
   return 1;
 }
 
 int tslua_push_querycursor(lua_State *L)
 {
-  TSNode node;
+  TSNode node = node_check(L, 1);
-  if (!node_check(L, 1, &node)) {
-    return luaL_error(L, "TSNode expected");
-  }
 
   TSQuery *query = query_check(L, 2);
-  if (!query) {
-    return luaL_error(L, "TSQuery expected");
-  }
-
   TSQueryCursor *cursor = ts_query_cursor_new();
   ts_query_cursor_exec(cursor, query, node);
 
@@ -1388,7 +1239,7 @@ int tslua_push_querycursor(lua_State *L)
 
   if (lua_gettop(L) >= 5 && !lua_isnil(L, 5)) {
     if (!lua_istable(L, 5)) {
-      return luaL_error(L, "table expected");
+      return luaL_argerror(L, 5, "table expected");
     }
     lua_pushnil(L);  // [dict, ..., nil]
     while (lua_next(L, 5)) {
@@ -1443,7 +1294,6 @@ static void push_querymatch(lua_State *L, TSQueryMatch *match, int uindex)
 static int querycursor_next_capture(lua_State *L)
 {
   TSQueryCursor *cursor = querycursor_check(L, 1);
-
   TSQueryMatch match;
   uint32_t capture_index;
   if (!ts_query_cursor_next_capture(cursor, &match, &capture_index)) {
@@ -1477,6 +1327,9 @@ static int querycursor_next_match(lua_State *L)
 static TSQueryCursor *querycursor_check(lua_State *L, int index)
 {
   TSQueryCursor **ud = luaL_checkudata(L, index, TS_META_QUERYCURSOR);
+  if (!ud || !(*ud)) {
+    luaL_argerror(L, index, "TSQueryCursor expected");
+  }
   return *ud;
 }
 
@@ -1487,17 +1340,26 @@ static int querycursor_gc(lua_State *L)
   return 0;
 }
 
-static int querymatch_info(lua_State *L)
+static TSQueryMatch *querymatch_check(lua_State *L, int index)
 {
   TSQueryMatch *ud = luaL_checkudata(L, 1, TS_META_QUERYMATCH);
-  lua_pushinteger(L, ud->id);
+  if (!ud) {
-  lua_pushinteger(L, ud->pattern_index + 1);
+    luaL_argerror(L, index, "TSQueryMatch expected");
+  }
+  return ud;
+}
+
+static int querymatch_info(lua_State *L)
+{
+  TSQueryMatch *match = querymatch_check(L, 1);
+  lua_pushinteger(L, match->id);
+  lua_pushinteger(L, match->pattern_index + 1);
   return 2;
 }
 
 static int querymatch_captures(lua_State *L)
 {
-  TSQueryMatch *match = luaL_checkudata(L, 1, TS_META_QUERYMATCH);
+  TSQueryMatch *match = querymatch_check(L, 1);
   lua_newtable(L);  // [match, nodes, captures]
   for (size_t i = 0; i < match->capture_count; i++) {
     TSQueryCapture capture = match->captures[i];
@@ -1523,11 +1385,7 @@ int tslua_parse_query(lua_State *L)
     return luaL_error(L, "string expected");
   }
 
-  const char *lang_name = lua_tostring(L, 1);
+  TSLanguage *lang = lang_check(L, 1);
-  TSLanguage *lang = pmap_get(cstr_t)(&langs, lang_name);
-  if (!lang) {
-    return luaL_error(L, "no such language: %s", lang_name);
-  }
 
   size_t len;
   const char *src = lua_tolstring(L, 2, &len);
@@ -1625,16 +1483,15 @@ static void query_err_string(const char *src, int error_offset, TSQueryError err
 static TSQuery *query_check(lua_State *L, int index)
 {
   TSQuery **ud = luaL_checkudata(L, index, TS_META_QUERY);
-  return ud ? *ud : NULL;
+  if (!ud || !(*ud)) {
+    luaL_argerror(L, index, "TSQuery expected");
+  }
+  return *ud;
 }
 
 static int query_gc(lua_State *L)
 {
   TSQuery *query = query_check(L, 1);
-  if (!query) {
-    return 0;
-  }
-
   ts_query_delete(query);
   return 0;
 }
@@ -1648,9 +1505,6 @@ static int query_tostring(lua_State *L)
 static int query_inspect(lua_State *L)
 {
   TSQuery *query = query_check(L, 1);
-  if (!query) {
-    return 0;
-  }
 
   // TSQueryInfo
   lua_createtable(L, 0, 2);  // [retval]