#15286: "Can't use Natural in base" when compiling GHC.Natural with -O0 -------------------------------------+------------------------------------- Reporter: alpmestan | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: libraries/base | Version: 8.5 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Building GHC | Unknown/Multiple failed | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4880 Wiki Page: | -------------------------------------+------------------------------------- Comment (by rockbmb): As part of ticket #15622 that I opened, I ran into this issue when I introduced an import to `GHC.TypeNats` in `libraries/base/Data/Fixed.hs`, having used it to replace an import to `GHC.TypeLits`. I also added two extensions, `{-# LANGUAGE DataKinds #-}` and `{-# LANGUAGE KindSignatures #-}`, which may be part of the problem. The associated commit is [here](https://gitlab.haskell.org/rockbmb/ghc/commit/c6726d732273785b53986f152a6e03...), and the failure I got in CI was: ``` HC [stage 1] libraries/base/dist-install/build/Data/Fixed.o HC [stage 1] libraries/base/dist-install/build/Data/Complex.o ghc-stage1: panic! (the 'impossible' happened) (GHC version 8.7.20190206 for x86_64-unknown-linux): Can't use Natural in base Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug make[1]: *** [libraries/base/dist-install/build/Data/Fixed.o] Error 1 make[1]: *** Waiting for unfinished jobs.... libraries/base/ghc.mk:4: recipe for target 'libraries/base/dist- install/build/Data/Fixed.o' failed make: *** [all] Error 2 Makefile:123: recipe for target 'all' failed ```. I included the error here because CI build logs in GitLab disappear after 1 week. I hope this helps, and if there's anything I can do to help close this issue I'll be happy to help. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15286#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler