Re: [GHC] #10982: Warn about unused pattern variables in type families

#10982: Warn about unused pattern variables in type families -------------------------------------+------------------------------------- Reporter: jstolarek | Owner: msosn Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | UnusedTyVarWarnings, | UnusedTyVarWarningsNamedWCs Blocked By: | Blocking: Related Tickets: #11098 | Differential Rev(s): Phab:D1576 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"eb7796f13e701cce4e7d1d86f36c966aa17f1e9c/ghc" eb7796f/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="eb7796f13e701cce4e7d1d86f36c966aa17f1e9c" Warn about unused type variables in type families The warnings are enabled with the flag -fwarn-unused-matches, the same one that enables warnings on the term level. Identifiers starting with an underscore are now always parsed as type variables. When the NamedWildCards extension is enabled, the renamer replaces those variables with named wildcards. An additional NameSet nwcs is added to LocalRdrEnv. It's used to keep names of the type variables that should be replaced with wildcards. While renaming HsForAllTy, when a name is explicitly bound it is removed from the nwcs NameSet. As a result, the renamer doesn't replace them in the quantifier body. (Trac #11098) Fixes #10982, #11098 Reviewers: alanz, bgamari, hvr, austin, jstolarek Reviewed By: jstolarek Subscribers: goldfire, mpickering, RyanGlScott, thomie Differential Revision: https://phabricator.haskell.org/D1576 GHC Trac Issues: #10982 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10982#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler