The "... foo ..." in my example was intended to show that module M does look up 'foo'.
From: Manuel M T Chakravarty [mailto:c...@cse.unsw.edu.au] Sent: 25 July 2012 08:26 To: Sittampalam, Ganesh Cc: Lennart Augustsson; Haskell Prime Subject: Re: Proposal: Scoping rule change If Lennart's suggestion is combined with GHC's lazy checking for name clashes (i.e., only check if you ever look a name up in a particular scope), it would also work in your example. Manuel "Sittampalam, Ganesh" <ganesh.sittampa...@credit-suisse.com>: If you're using unqualified and unrestricted imports, there's still the risk that another module will export something you care about, e.g. module M where import I -- currently exports foo import J -- might be changed in future to export foo ... foo ... So I think you need to use import lists or qualified anyway to avoid any risk of future name clashes - given that, does this change buy much? From: haskell-prime-boun...@haskell.org <mailto:haskell-prime-boun...@haskell.org> [mailto:haskell-prime-boun...@haskell.org <mailto:prime-boun...@haskell.org> ] On Behalf Of Lennart Augustsson Sent: 24 July 2012 02:29 To: Haskell Prime Subject: Proposal: Scoping rule change It's not often that one gets the chance to change something as fundamental as the scoping rules of a language. Nevertheless, I would like to propose a change to Haskell's scoping rules. The change is quite simple. As it is, top level entities in a module are in the same scope as all imported entities. I suggest that this is changed to that the entities from the module are in an inner scope and do not clash with imported identifiers. Why? Consider the following snippet module M where import I foo = True Assume this compiles. Now change the module I so it exports something called foo. After this change the module M no longer compiles since (under the current scoping rules) the imported foo clashes with the foo in M. Pros: Module compilation becomes more robust under library changes. Fewer imports with hiding are necessary. Cons: There's the chance that you happen to define a module identifier with the same name as something imported. This will typically lead to a type error, but there is a remote chance it could have the same type. Implementation status: The Mu compiler has used the scoping rule for several years now and it works very well in practice. -- Lennart ======================================================================== ====== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html <http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html> ======================================================================== ====== _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org <mailto:Haskell-prime@haskell.org> http://www.haskell.org/mailman/listinfo/haskell-prime <http://www.haskell.org/mailman/listinfo/haskell-prime> =============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ===============================================================================
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