#8634: Relax functional dependency coherence check ("liberal coverage condition") -----------------------------------+--------------------------------------- Reporter: danilo2 | Owner: Type: feature | Status: new request | Milestone: 7.10.1 Priority: high | Version: 7.7 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: None/Unknown | Related Tickets: #1241, #2247, #8356 Test Case: | Blocking: | -----------------------------------+--------------------------------------- Comment (by goldfire): I take back my claim that `-XDysfunctionalDependencies` cannot cause type errors. While it's true that fundeps do not exist in Core, it's conceivable that dysfundeps could cause invalid Core to be produced, leading to errors caught by `-dcore-lint`. I have not thought this out in great detail, but I think I was too quick to judgment in comment:7. To summarize: it's possible that dysfundeps are type-safe, and it's possible that they are not. I have not thought hard enough about the problem to stake a claim on one answer or another: my reasoning in comment:7 is bogus, though perhaps my conclusion is correct. In any case, I don't wish to be cited as the person who thinks that these are safe! :) I still ''do'' think that, if someone discovers these ''are'' safe, they might become an interesting tool. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8634#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler