#13509: Perplexing type error with unboxed tuples -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 Resolution: | Keywords: | LevityPolymorphism Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones <simonpj@…>): In [changeset:"bac95f9de5bd8d0a647a3a1e4492497603c2fda2/ghc" bac95f9d/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="bac95f9de5bd8d0a647a3a1e4492497603c2fda2" Yet another attempt at inferring the right quantification TcSimplify.decideQuantification is truly a tricky function! Trac #13509 showed that we were being over-eager with defaulting of runtime-rep variables (levity polymorphism), which meant that a program was wrongly rejected, and with a very odd error message (c.f. Trac #13530) I spent an unreasonably long time figuring out how to fix this in a decent way, and ended up with a major refactoring of decideQuantification, with a kock-on effect in simplifyInfer. It is at least a bit more comprehensible now; but I still can't say I like it. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13509#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler