Well spotted!
Yes, I changed this some time ago. Handling polymorphic subsumption
when matching patterns just turned to be a lot of hassle, with little
obvious payoff. Types in patterns must now match exactly.
I could conceivably back-pedal on this, but you are the first person to
even notice the change (or at least to comment on it).
Simon
| -Original Message-
| From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Bruno Oliveira
| Sent: 21 January 2006 18:44
| To: Haskell Mailing List
| Subject: [Haskell] Pattern Matching with rank-2 types
|
| Hello,
|
| The following function is a valid function in ghc6.2.2:
|
| > func :: (forall a . [a]) -> [b]
| > func [] = []
|
| However, in ghc6.4.1 it does not work anymore:
|
| Iterators4.lhs:56:6:
| Couldn't match `forall a. [a]' against `[a]'
| When checking the pattern: []
| In the definition of `func': func [] = []
|
| Is this supposed to happen?
|
| Cheers,
|
| Bruno
|
|
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