#5331: Warning for unused existentially quantified types
---------------------------------+------------------------------------------
Reporter: Lemming | Owner:
Type: feature request | Status: new
Priority: normal | Component: Compiler
Version: 6.12.3 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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I found a bug in my code that boils down to:
{{{
{-# LANGUAGE ExistentialQuantification #-}
data X = forall a b. X a
}}}
Obviously the type 'b' is not used. It didn't hurt, but it could have
been, that I intended to do something with the 'b' and then forgot it. I
would like to get a warning in this situation like "Unused type variable
'b'".
It might even be, that no existential quantification is needed at all, as
in the following case:
{{{
data Y = forall a. Y
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5331>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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