#13990: Core Lint error on empty case -------------------------------------+------------------------------------- Reporter: mbieleck | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.2.2 Component: Compiler | Version: 8.2.1-rc3 Resolution: | Keywords: core-lint | case Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Without reading all the commentary above: I conjecture that the only way to get this right is to come up with some datatype which serves as evidence that an empty case is acceptable. There may be several constructors of the datatype depending on why GHC believes the empty case, and we may need to do transformations to elements of this type during simplification, etc. In other words, it's all quite like what `Coercion` does for type equality. Then, Lint could check various invariants of the datatype. (Also known as typing rules.) Is this worth it? It certainly doesn't seem like it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13990#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler