#11572: BangPatterns-related behavior regressions on GHC 8.0 -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 8.0.1-rc2 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): Another strange facet of the GHCi portion of the bug: the behavior is different depending on whether a wildcard or a named type variable is used. Here's another bizarre error you can get in GHCi (but not compiled code): {{{ λ> :set -XMagicHash -XBangPatterns λ> import GHC.Prim λ> let !a = (undefined :: Int#) in print 2 <interactive>:3:5: error: • You can't mix polymorphic and unlifted bindings !a = (undefined :: Int#) Probable fix: add a type signature • In the expression: let !a = (undefined :: Int#) in print 2 In an equation for ‘it’: it = let !a = (undefined :: Int#) in print 2 }}} This works without issue in GHCi 7.10.3. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11572#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler