#8884: Reifying closed type families is broken -------------------------------------+------------------------------------ Reporter: goldfire | Owner: goldfire Type: bug | Status: merge Priority: normal | Milestone: 7.8.1 Component: Template Haskell | Version: 7.8.1-rc2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Changes (by goldfire): * status: new => merge Comment: The fix affects ''open'' type families as well as closed. Both families had exactly the same mis-behavior, upon inspection of the code. Given that, it's unclear to me whether this should be merged. The old behavior was clearly wrong -- for example, reifying a type family and then trying to splice it would end in failure. But, the old behavior was also quite reliable, and it's conceivable that users have noticed the poor behavior and have coded against it. (In fact, a co-author of one of my libraries has done just that, which is how I discovered the GHC bug!) So, we must choose between * Retaining the incorrect behavior (which has been around for some time), while not surprising users in the final 7.8 release, or * Having correct behavior. I slightly favor the latter, believing that this error was so egregious that no one (other than me, evidently) is using this feature of GHC. If anyone else were using the feature, we would have seen the bug report! So, I'm setting this ticket to `merge` but am happy to have others disagree about that decision. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8884#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler