This Flycheck extension shows errors under point in pos-tip popups.
As usual, from MELPA.
In your Cask file:
(source gnu)
(source melpa)
(depends-on "flycheck-pos-tip")
In your init.el
:
(with-eval-after-load 'flycheck
(flycheck-pos-tip-mode))
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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See COPYING for details.