GHC/Error messages

From HaskellWiki

GHC error messages and their meaning.

1 "Parse error in pattern"

TODO

Example: TODO

2 "Foo' is not a (visible) method of class `Bar'"

This error message occurs when one tries to instantiate a class, but did not import the functions one tries to implement.

Example:

import Prelude hiding ((==)) 
data Foo = Foo 
instance Eq Foo where 
    (==) a b = True