`ghc: panic!` when loading module

I'm learning Haskell from an online book (haskellbook.com) and when I loaded an answers module, this happened:

Prelude> :l ex.hs 
[1 of 1] Compiling Ex               ( ex.hs, interpreted )
ghc: panic! (the 'impossible' happened)
  (GHC version 8.2.1 for x86_64-apple-darwin):
	repSplitAppTys
  a_a1qJ[sk:1]
  Bool
  []
  Call stack:
      CallStack (from HasCallStack):
        prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable
        callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable
        pprPanic, called at compiler/types/Type.hs:808:9 in ghc:Type

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

> 

notice that the Prelude module got unloaded. The source code for my ex.hs module:

module Ex where

import Data.Char

myAny :: (a -> Bool) [a] -> Bool
myAny pred [] = False
myAny pred (x:xs) = pred x || myAny pred xs

You'll notice that I missed a -> in myAny's type signature.

Trac metadata

Trac field	Value
Version	8.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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