[ ghc-Bugs-1236718 ] TcSimplify.lhs:(2093, 13)-(2094, 38): Non-exhaustive patterns

Bugs item #1236718, was opened at 2005-07-12 06:48
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Category: Compiler (Type checker)
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: TcSimplify.lhs:(2093,13)-(2094,38): Non-exhaustive patterns

Initial Comment:
Dear ghc developers,

instead of giving some kind of 'unresolved overloading'
error message, the following code

% cat Bug.hs
{-# OPTIONS_GHC -fglasgow-exts #-}
module Bug where

class Foo a
instance Foo (a -> b)

foo :: Foo a => a -> ()
foo = undefined

class Bar a r
-- The same happens if we use fundeps:
-- class Bar a r | r -> a

bar :: Bar a r => r -> ()
bar = undefined

test = foo bar

causes ghc to panic:

% ghc Bug.hs
ghc-6.5.20050709: panic! (the `impossible' happened,
GHC version 6.5.20050709):
        typecheck/TcSimplify.lhs:(2093,13)-(2094,38):
Non-exhaustive patterns in case


Best regards,

Thomas Jäger

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