#7021: Tuple (and other exotic predicates) not yet handled in Template Haskell -------------------------+------------------------------------------------- Reporter: | Owner: goldfire | Status: new Type: | Milestone: 7.8.1 feature request | Version: 7.5 Priority: | Keywords: ConstraintKinds normal | TemplateHaskell Component: | Architecture: Unknown/Multiple Template Haskell | Difficulty: Unknown Resolution: | Blocked By: Operating System: | Related Tickets: Unknown/Multiple | Type of failure: | None/Unknown | Test Case: | Blocking: | -------------------------+------------------------------------------------- Comment (by simonpj): I rather agree with Richard: make `Pred` and `Type` into synonyms. That's what GHC does internally, and it works pretty well. However that would be a bit of a bump: people's programs would break. A possible half-way house would be to have {{{ data Pred = TypeP Type | ClassP Name [Type] | EqualP Type Type }}} and then deprecated `ClassP` and `EqualP` in favour of the equivalents in `Type`. Once that has settled down, making `Pred` into a synonym would still be a breaking change, but a very routine one to absorb. Or it might be better to do it all at once. I'm not sure, and would welcome opinions. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7021#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler