yesodweb/yesod — pull request #374 by HairyDude (2012-06-18 21:50:50+00:00)
Title: import (<>) from Data.Monoid with GHC >= 7.0.4

Import.hs defines its own (<>) if your GHC is too old to have (<>) in Data.Monoid, but unfortunately it never imports (<>) even with recent GHC. So with >7.0.4 you perversely get no (<>). This patch should fix this.