#2523: Improve warnings for use of "forall" without -XExistentialQuantification
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Reporter: dmhouse | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.8.3 | Severity: minor
Keywords: | Testcase:
Architecture: Unknown | Os: Unknown
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Here's a GHCi session:
{{{
Prelude> let foo :: forall a. a; foo = undefined
<interactive>:1:19:
Illegal operator `.' in type `forall a . a'
(Use -XTypeOperators to allow operators in types)
Prelude> let foo :: forall a. Show a => a; foo = undefined
<interactive>:1:28: parse error on input `=>'
}}}
Both of these errors could be improved, I think, by detecting the use of
'forall' as a type variable name, and suggesting
-XExistentialQuantification if it's being used.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2523>
GHC <http://www.haskell.org/ghc/>
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