#2588: Missed suggestion with context on foralls
-----------------------------+----------------------------------------------
Reporter: NeilMitchell | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.9 | Severity: normal
Keywords: | Testcase:
Architecture: Unknown | Os: Unknown
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Given the program:
{{{
module Test where
test :: forall a . a -> a
test = id
}}}
I get the nice and helpful error message:
{{{
Test.hs:3:17:
Illegal operator `.' in type `forall a . (a -> a)'
Perhaps you intended to use -XRankNTypes or similar flag
to enable explicit-forall syntax: forall <tvs>. <type>
}}}
[I personally usually want ScopedTypeVariables rather than RankNTypes, but
its still a very useful hint at where to look]
However, trying the program:
{{{
module Test where
test :: forall a . Eq a => a -> a
test = id
}}}
Gives:
{{{
Test.hs:3:24: parse error on input `=>'
}}}
I think it would be helpful to give the same suggestion as above.
-- Neil
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2588>
GHC <http://www.haskell.org/ghc/>
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