Re: [GHC] #13371: instance selection too eager

#13371: instance selection too eager -------------------------------------+------------------------------------- Reporter: aavogt | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.2 checker) | 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 RyanGlScott): Actually, compiling these commits from the HEAD branch (instead of the 8.0.2 branch) turned out to be more fruitful. I discovered that the commit which introduced this regression is c9bcaf3165586ac214fa694e61c55eb45eb131ab: {{{ From c9bcaf3165586ac214fa694e61c55eb45eb131ab Mon Sep 17 00:00:00 2001 From: Bartosz Nitka Date: Tue, 26 Apr 2016 05:58:24 -0700 Subject: [PATCH] Kill varSetElemsWellScoped in quantifyTyVars varSetElemsWellScoped introduces unnecessary non-determinism in inferred type signatures. Removing this instance required changing the representation of TcDepVars to use deterministic sets. This is the last occurence of varSetElemsWellScoped, allowing me to finally remove it. Test Plan: ./validate I will update the expected outputs when commiting, some reordering of type variables in types is expected. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13371#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler