#15057: Lint types created by newFamInst -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.1 Keywords: TypeFamilies | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #15012 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In #15012, we observed a terrible failure resulting from `newFamInst` creating a type family instance with an unbound type variable on the right-hand side. What's worse, `-dcore-lint` didn't catch it! Let's fix that by calling `lintType` on the types involved in `newFamInst`. A wrinkle in this plan is that `lintType` currently expands all type synonyms, but the offending type in #15012 had the unbound variable occur in a type synonym application, so expanding type synonyms would make this naughtiness seemingly vanish (from Core Lint's perspective). We should configure `lintType` so that one can control its type synonym expansion behavior. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15057 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler