#13658: Assertion failure on HEAD: "optCoercion changed types!" -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.3 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: | -------------------------------------+------------------------------------- Comment (by bgamari): Indeed this appears to resolve the issue, {{{#!patch diff --git a/compiler/types/OptCoercion.hs b/compiler/types/OptCoercion.hs index b1aa646a97..03e1d6cb5f 100644 --- a/compiler/types/OptCoercion.hs +++ b/compiler/types/OptCoercion.hs @@ -378,6 +378,7 @@ opt_univ env sym prov role oty1 oty2 | Just (tc1, tys1) <- splitTyConApp_maybe oty1 , Just (tc2, tys2) <- splitTyConApp_maybe oty2 , tc1 == tc2 + , equalLength tys1 tys2 -- NB: prov must not be the two interesting ones (ProofIrrel & Phantom); -- Phantom is already taken care of, and ProofIrrel doesn't relate tyconapps = let roles = tyConRolesX role tc1 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13658#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler