#7989: "No constructor has all these fields" message can be improved ---------------------------------+------------------------------------------ Reporter: akio | Owner: Type: feature request | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 7.7 Keywords: | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: Other Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: | ---------------------------------+------------------------------------------ Comment(by simonpj): OK.... It's not easy to understand that code! Maybe it would be worth a few more named intermediate values, with types, and a comment? You could produce a very big set when a very small set exists, couldn't you? Could you ameliorate that as follows? Use `T` to mean the data type of the first field in `rbinds`. * Sort the `membership` list in order of increasing number of `True` fields. So the earlier fields `f` in the list have few `T` constructors that have field `f`. * Now a field with a different type will be right at the front of the list. * And the `(&&)` process will terminate more quickly because of all the `False` items. Simon -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7989#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler