Flycheck extension for Apple’s Xcode.
(use-package flycheck-xcode
:ensure t
:commands (flycheck-xcode-setup)
:init
(mapc
(lambda (x)
(add-hook x #'flycheck-xcode-setup))
'(c-mode-hook c++-mode-hook objc-mode-hook swift-mode-hook)))
These are screenshots comparing Emacs vs Xcode’s display of errors/warnings.