#15799: GHC panic (and warnings) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #12045 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Discussion this morning essentially agreed with my "first instinct" above. But with a new spin on things: The `tcm_smart` setting on `TyCoMapper` is really about what to do about `Refl` casts. Do we preserve them? Discard them? Or, in our new mode, discard some of them? Previously, the "dumb" mode meant to preserve all casts. This is important for `Note [The well- kinded type invariant]` (where we sometimes use reflexive casts to make a type's kind looked zonked even when the type is not yet zonked). The "smart" mode dropped all reflexive casts. Now, we want a third mode that drops all casts that look reflexive to the type checker. By elucidating what we really mean by "smart", having a third setting does not look so unusual, after all. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15799#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler