[GHC] #16275: type hole in hs-boot file triggers GHC internal error

1 Feb 2019


      #16275: type hole in hs-boot file triggers GHC internal error
-------------------------------------+-------------------------------------
           Reporter:  j.waldmann     |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.6.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Put each line in a separate file, the last one is B.hs-boot
 {{{
 module A where { import {-# SOURCE #-} B }

 module B where { }

 module B where { data T a ; foo :: T _ }
 }}}
 then
 {{{
 $ ghci A.hs

 GHCi, version 8.6.3: http://www.haskell.org/ghc/  :? for help
 [1 of 3] Compiling B[boot]          ( B.hs-boot, interpreted )

 B.hs-boot:1:38: error:
     • GHC internal error: ‘_’ is not in scope during type checking, but it
 passed the renamer
       tcl_env of environment: []
     • In the first argument of ‘T’, namely ‘_’
       In the type signature: foo :: T _
   |
 1 | module B where { data T a ; foo :: T _ }
   |                                      ^
 }}}
 I know the program is invalid (the hole has no valid instance) but still
 it should not produce an internal error?

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16275
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler