#11948: GHC forgets constraints -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: closed Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 7.10.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | typecheck/should_fail/T11948 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones <simonpj@…>): In [changeset:"643706e44935cd15c2248e5345dadd3e9804688e/ghc" 643706e4/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="643706e44935cd15c2248e5345dadd3e9804688e" Narrow the warning for simplifiable constraints In Trac #11948 I added the warning -Wsimplifiable-class-constraints which warns if the class constraints in a type signature are simplifiable. But in fact the fragility it warns about only happens with NoMonoLocalBinds, so this patch switches off the warning if you have MonoLocalBinds (and suggests using it in the error message). See Note [Simplifiable given constraints] in TcValidity. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11948#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler