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] 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 > ============================================================================== > > _______________________________________________ > Haskell-prime mailing list > Haskell-prime@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-prime
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