Re: [GHC] #15361: Error message displays redundant equality constraint

#15361: Error message displays redundant equality constraint -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: 8.8.1 Component: Compiler (Type | Version: 8.4.3 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Poor/confusing | Unknown/Multiple error message | Test Case: Blocked By: | Blocking: Related Tickets: #14394 | Differential Rev(s): Phab:D5002 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Krzysztof Gogolewski ): In [changeset:"c552feea127d8ed8cbf4994a157c4bbe254b96c3/ghc" c552feea/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c552feea127d8ed8cbf4994a157c4bbe254b96c3" Suppress redundant givens during error reporting Summary: When GHC reports that it cannot solve a constraint in error messages, it often reports what given constraints it has in scope. Unfortunately, sometimes redundant constraints (like `* ~ *`, from #15361) can sneak in. The fix is simple: blast away these redundant constraints using `mkMinimalBySCs`. Test Plan: make test TEST=T15361 Reviewers: simonpj, bgamari Subscribers: rwbarton, thomie, carter GHC Trac Issues: #15361 Differential Revision: https://phabricator.haskell.org/D5002 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15361#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler