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  • Glasgow Haskell Compiler
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  • #508

Closed
Open
Created Feb 10, 2001 by qrczak@trac-qrczak

class C a b | a -> b; (C a b, Eq b) => a -- not legal

The following fragment is not accepted:

class C a b | a -> b where f :: a -> b
g :: (C a b, Eq b) => a -> Bool
g x = f x == f x

    Ambiguous type variable(s) `b' in the constraint `Eq b'
    arising from use of `==' at Test.hs:4
    In the right-hand side of an equation for `g': (f x) == (f x)

Hugs accepts it.
Trac metadata
Trac field Value
Version None
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution ResolvedFixed
Component Compiler (Type checker)
Test case
Differential revisions
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