[ ghc-Bugs-1208771 ] forall in pattern type sig has changed from 6.2.2

Bugs item #1208771, was opened at 2005-05-25 21:30
Message generated for change (Comment added) made by simonpj
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Category: Compiler (Type checker)
Group: 6.4
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Mark Tullsen (mtullsen)
Assigned to: Nobody/Anonymous (nobody)
Summary: forall in pattern type sig has changed from 6.2.2

Initial Comment:
------ The program (straight from documentation :-) ------
$ cat Test.hs

test = \(f :: forall a. a -> a) -> (f True,f 'a')

------ Works fine under 6.2.2 ------
tests $ ghci-6.2.2 -fglasgow-exts Test.hs
...
Compiling Test             ( Test.hs, interpreted )
Ok, modules loaded: Test.

------ Doesn't typecheck under 6.4 ------
$ ghci-6.4 -fglasgow-exts Test.hs
...
Compiling Test             ( Test.hs, interpreted )

Test.hs:3:9:
    Inferred type is less polymorphic than expected
      Quantified type variable `a' is mentioned in the environment:
        test :: (a -> a) -> t (bound at Test.hs:3:0)
      Expected type: forall a1. a1 -> a1
      Inferred type: a -> a
    In a lambda abstraction: \ (f :: forall a. a -> a) -> (f True, f 'a')
    In the definition of `test': test = \ (f :: forall a. a -> a) -> (f True, f 
'a')
...


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>Comment By: Simon Peyton Jones (simonpj)
Date: 2005-05-26 21:39

Message:
Logged In: YES 
user_id=50165

Ah yes.  Thank you.  In a cleanup of TcBInds I failed to take 
account of this case; the old code did it fine.

Fixed now. tc194 is the test case

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