#8827: Inferring Safe mode with GeneralizedNewtypeDeriving is wrong -------------------------------------+------------------------------------ Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: 7.8.1-rc1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by goldfire): From the manual, describing the guarantees of Safe Haskell: Module boundary control — Haskell code compiled using the safe language is guaranteed to only access symbols that are publicly available to it through other modules export lists. An important part of this is that safe compiled code is not able to examine or create data values using data constructors that it cannot import. If a module M establishes some invariants through careful use of its export list then code compiled using the safe language that imports M is guaranteed to respect those invariants. Because of this, Template Haskell and !GeneralizedNewtypeDeriving are disabled in the safe language as they can be used to violate this property. Without the check to make sure that all relevant constructors are in scope, the above property would be false. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8827#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler