Re: [GHC] #7888: Impredicativity flag needed more often

#7888: Impredicativity flag needed more often ----------------------------------------------+----------------------------- Reporter: monoidal | Owner: Type: bug | Status: new Priority: normal | Component: Compiler (Type checker) Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Blockedby: Blocking: | Related: ----------------------------------------------+----------------------------- Comment(by simonpj@…): commit a18ea4f20b73e1b3ef5cda2389c713152eb9576e {{{ Author: Simon Peyton Jones Date: Wed May 15 09:51:25 2013 +0100 Make 'undefined' have the magical type 'forall (a:OpenKind).a' This fixes Trac #7888, where the user wanted to use 'undefined' in a context that needed ((forall a. a->a) -> Int). We allow OpenKind unification variables to be instantiate with polytypes (or unboxed types), hence the change. 'error' has always been like this; this change simply extends the special treatment to 'undefined'. It's still magical; you can't define your own wrapper for 'error' and get the same behaviour. Really just a convenience hack. compiler/coreSyn/MkCore.lhs | 48 ++++++++++++++++++++++++++++++++------- compiler/prelude/PrelNames.lhs | 5 ---- 2 files changed, 39 insertions(+), 14 deletions(-) }}} -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7888#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler