Latest release: 0.23 (changelog)
Flycheck is a modern on-the-fly syntax checking extension for GNU Emacs, intended as replacement for the older Flymake extension which is part of GNU Emacs.
It uses various syntax checking and linting tools to automatically check the contents of buffers while you type, and reports warnings and errors directly in the buffer, or in an optional error list:
With Flycheck installed you can read the manual of your Flycheck installation
inside Emacs with