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 |
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Differential revisions |
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BlockedBy |
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Related |
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Blocking |
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CC |
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Operating system |
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Architecture |
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