#12130: ghc: panic! (the 'impossible' happened): find_tycon Block [] -------------------------------------+------------------------------------- Reporter: jeiea | Owner: Type: bug | Status: patch Priority: high | Milestone: 8.0.2 Component: Template Haskell | Version: 8.0.1 Resolution: | Keywords: | DisambiguateRecordFields Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash | Test Case: th/T12130 Blocked By: | Blocking: Related Tickets: #11228 | Differential Rev(s): Phab:D2321 Wiki Page: | -------------------------------------+------------------------------------- Changes (by adamgundry): * status: new => patch * testcase: => th/T12130 * differential: => Phab:D2321 Comment: Thanks for the great test case! It turns out this bug was lingering already in 7.10, but laziness meant we didn't hit the panic by sheer luck. Simple fix: replace the panic with `Nothing`, which is reasonable in this context: if the datacon isn't in scope, don't use it for disambiguating record fields. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12130#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler