Re: [GHC] #11150: New `-fwarn-noncanonical-monoid-instances` warning

#11150: New `-fwarn-noncanonical-monoid-instances` warning -------------------------------------+------------------------------------- Reporter: hvr | Owner: hvr Type: feature request | Status: patch Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #11128, #11139 | Differential Rev(s): Phab:D1553 Wiki Page: | prime:Libraries/Proposals/SemigroupMonoid| -------------------------------------+------------------------------------- Comment (by Herbert Valerio Riedel ): In [changeset:"986ceb1679b501414b996c520b08ce929a40f94c/ghc" 986ceb16/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="986ceb1679b501414b996c520b08ce929a40f94c" Implement new `-fwarn-noncanonical-monoid-instances` This is similiar to the `-fwarn-noncanonical-monad-instances` warning implemented via #11128, but applies to `Semigroup`/`Monoid` instead and the `(<>)`/`mappend` methods (of which `mappend` is planned to move out of `Monoid` at some point in the future being redundant and thus error-prone). This warning is contained in `-Wcompat` but not in `-Wall`. This addresses #11150 Reviewed By: quchen Differential Revision: https://phabricator.haskell.org/D1553 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11150#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler