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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?

Trac metadata

Trac field	Value
Version	8.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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