#14218: GHC.Stack.HasCallStack not compatible with constraint synonyms -------------------------------------+------------------------------------- Reporter: ntc2 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * cc: gridaphobe, simonpj (added) Comment: Hmm, yes, this is an unfortunate consequence of the implementation of the `HasCallStack` implementation. I suspect we find the `C` dictionary in scope when we solve for `callStack`'s constraints in `f`. Consequently we just pass it as a whole to `callStack` and the special callstack solver logic is never invoked. I honestly don't know how best to avoid this, but it certainly suggests that the status quo is rather fragile. I fear this issue may be somewhat intrinsic in the implementation strategy. If this is case we should at very least make sure this wrinkle is well-documented. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14218#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler