#15073: Unable to newtype derive `Prim` via DerivingStrategies -------------------------------------+------------------------------------- Reporter: fosskers | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 Resolution: | Keywords: deriving Operating System: Unknown/Multiple | Architecture: x86_64 | (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * keywords: => deriving Comment: Indeed. The fix for #14579 requires generating code for `GeneralizeNewtypeDeriving` that has more explicit type/kinds signatures. The flipside is that `Prim`, whose types mention unboxed tuples and levity polymorphic kinds, now requires enabling `TypeInType` and `UnboxedTuples` to derive, as you've observed. There are a handful of language extensions that GHC always enables under the hood when deriving things (such as `KindSignatures`), but I'm very much doubtful that we'd want to always enable either `TypeInType` or `UnboxedTuples`, since those can cause some other programs to break. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15073#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler