#10079: Coercible solver regression: Couldn't match rep of () with Const () b -------------------------------------+------------------------------------- Reporter: glguy | Owner: goldfire Type: bug | Status: new Priority: high | Milestone: 7.10.1 Component: Compiler (Type | Version: 7.10.1-rc1 checker) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: indexed- valid program | types/should_compile/T10079 Blocked By: | Blocking: Related Tickets: #7788, #8550 | Differential Revisions: Phab:D653 -------------------------------------+------------------------------------- Comment (by goldfire): Just to clarify, the original report with this ticket ''is'' actually already fixed in the 7.10 branch (see comment:12). It's just that the fix in 7.10 is very incomplete, as Simon points out in comment:9. That said, the fix in 7.10 doesn't introduce ''new'' bad behavior. So, if we're happy to live with #7788, #8550, #9554, and #10139, then we can avoid merging this to 7.10. Personally, this is a hard call. If we don't merge, then various (ill- typed) programs will cause GHC to hang, sometimes mysteriously. In particular, #10139 has a program without `UndecidableInstances` but that hangs 7.10RC2. The patch at Phab:D653 allows the program to compile. But I see how this change could rock the boat! I certainly welcome other opinions about how to proceed. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10079#comment:22 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler