#14490: TTG Snags -------------------------------------+------------------------------------- Reporter: alanz | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #14482 | Differential Rev(s): Wiki Page: | ImplementingTreesThatGrow | -------------------------------------+------------------------------------- Comment (by alanz): My current thoughts on this As I understand it, the Data instances can only be generated for concrete types. As such the index type is a red herring, as we need the Data instances for the indexed type. Effectively, we are tailoring the AST to be a number of concrete versions. This is the point of TTG. So making a Data instance per concrete version may be the best way to go. Plan B. So, we know we can do that with GHC 8.2, and do not want to complicate life in terms of cherry-picking in the interim. So, perhaps either put this work on hold, or do it in a long-running branch until such time as GHC 8.2 is the minimal bootstrap compiler. Yay 6 months cycles. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14490#comment:28 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler