Created attachment 109862 [details]
Screenshot with missing syntax highlighting.

See the screenshot.
1. Syntax (or semantic?) highlighting is absent for some functions, e.g. Lua auxlib functions (it was absent for other Lua functions as well before some magic that I don’t remember exactly). Autocompletion and argument list works for them, however.
2. Those for which highlighting works are described as “Invalid type” (followed by “Type: Function”!) in the tooltip.

There may be several reasons for that.
a. I have several versions of Lua, one in `/usr/include` and others in subdirectories.
b. Lua uses weird syntax for functions, like
`LUALIB_API int (luaL_callmeta) (lua_State *L, int obj, const char *e);`
(notice the parentheses, like in pointer declaration).
c. Lua uses `#include` inside `extern "C"`.