#15629: "No skolem info" panic (GHC 8.6 only) -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler (Type | Version: 8.6.1-beta1 checker) | Resolution: | Keywords: TypeInType 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 RyanGlScott): Found it. It's commit 042df603cbb5a77ec13ccfec2ce7bad2bb940aae: {{{ From 042df603cbb5a77ec13ccfec2ce7bad2bb940aae Mon Sep 17 00:00:00 2001 From: Richard Eisenberg <rae@cs.brynmawr.edu> Date: Thu, 5 Jul 2018 14:21:43 -0400 Subject: [PATCH] Unwrap casts before checking vars in eager unifier Previously, checking whether (tv |> co) ~ (tv |> co) got deferred, because we looked for vars before stripping casts. (The left type would get stripped, and then tv ~ (tv |> co) would scare the occurs- checker.) This opportunity for improvement presented itself in other work. This is just an optimization. Some programs can now report more errors simultaneously. }}} Pretty impressive for "just an optimization" :) And yes, we should absolutely add a regression test for this, since I couldn't find another program of this caliber in the test suite currently. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15629#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler