malcolm 2004/06/16 07:23:10 PDT Modified files: src/compiler98 FixSyntax.hs Log: Fix a pattern-matching bug. Consider the following example: ------------------------------------------------ module Foo where newtype Blah = Blah Int deriving (Eq, Show) instance Num Blah where (Blah i) + (Blah j) = Blah (i + j) ... fromInteger x = Blah (fromInteger x) bar :: Blah -> Bool bar 0 = False bar _ = True ------------------------------------------------ nhc98 previously failed with: Fail: What? matchAltIf at 15:9 because the dictionary for (Num.fromInteger {dict:Blah} 0) in the pattern-match was being flattened to (Num.Blah.fromInteger 0), which made it impossible to later choose the right instance of (Eq.==). This fix ensures that fsExp knows whether it is in an expression context or a pattern-context, and for patterns it now refuses to flatten the dictionary. Revision Changes Path 1.21 +69 -71 nhc98/src/compiler98/FixSyntax.hs