Non-exhaultive patterns from derived Read

When switching from GHC 5.04.1 to 6.0 I started getting 
a load of warnings like these:




 source/SDL/Types.hs:33:


     Warning: Pattern match(es) are non-exhaustive


          In a pattern binding in


             a 'do' expression:


              Patterns not matched:


                  Text.Read.Lex.EOF


                  Text.Read.Lex.Rat _


                  Text.Read.Lex.Int _


                  Text.Read.Lex.Symbol _


                  ...




The source in question looks like this




data Expected


	= ExpectedType String


	| ExpectedValue String


	deriving (Read, Show)




It looks as though everything deriving Read causes this 
warning (there are several such constructs in the file).  
Deriving only Show does not.  Found no mention of 
change to behavior of derived reads in release notes or in 
google.




Cheers,


Jason Feingold


jfeingol@haverford.edu

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Trac field	Value
Version	None
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	ResolvedWon'tFix
Component	Compiler
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