indenting change causes internal error (#3959) · Issues · Glasgow Haskell Compiler / GHC

indenting change causes internal error

I found a bizarre little bug in GHC 6.12.1 on Mac OS X 10.6 (Haskell Platform 2010.1.0.0 i386). It only occurs when compiling through Cabal; it does not occur when using ghc --make or ghci.

The following code will compile without error but will generate a runtime error:

test = do
       E.throw Failure
       (return "No exception" :: IO String)
     `E.catches`
      [E.Handler (\Failure -> return "Exception")]

The following code will compile and run correctly:

test = do
      E.throw Failure
       (return "No exception" :: IO String)
     `E.catches`
      [E.Handler (\Failure -> return "Exception")]

The only difference between the 2 is that the second has one less leading space.

The generated error is:

test1: internal error: PAP object entered!
    (GHC version 6.12.1 for i386_apple_darwin)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
Abort trap

Deleting my ~/.ghc folder had no effect.

Trac metadata

Trac field	Value
Version	6.12.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
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Related
Blocking
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Operating system
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