#14759: ListSetOps WARNING causes tests to fail -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4628 Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
I think this can work, but we'd have to remove dups from A's imp_finsts before computing imp_finsts for B if B imports A. Otherwise for bigger module hierarchies a lot of duplicates will accumulate.
Yes, the idea is to allow dups to accumulate (which happens for free, just by `unionBags`) and then when ''consuming'' the bag simply avoid doing things twice. I think that's good, because generally we accumulate the `imp_fints` and then remove dups, sort, etc to make `dep_finists` for this module. But this approach does depend on the "accumulate and consume once" pattern.
Perhaps we could avoid explicitly storing the whole transitive closure if when checking type family consistency we did a traversal with pruning instead
Maybe so, but I'm not certain. For sure you'd want to know whether a module had family instances either in itself or in its transitive imports. Let's call that the "finst flag" Then, to look for imported instances, you could say * For each imported module M, if its finst-flag is off, ignore M. * Otherwise, check for family instances in M, and then * Consider each direct import of M That'd require you to traverse a path of .hi files to get to the one with the family instances in it. (Currently we can jump direct to the latter.) But perhaps that's fine. Looks like a good thing to explore. We could do the same for orphan-instance modules. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14759#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler