Qualified identifiers opinion

[Christian Maeder]

Simon Marlow wrote:
> I believe the solution we adopted for GHC 6.8.1 (and I proposed for
> Haskell') strikes the right balance.
> 
> M.where is lexed as an identifier.  This doesn't require adding any
> exceptions or corner cases to either the implementation or the
> specification of the grammar.  It is much easier to implement than the
> existing Haskell 98 rule (I deleted 30 lines of code from GHC's lexer to
> implement it).  It's easy to understand.  It removes an opportunity for
> obfuscation.  It must be the right thing!

Yes, and fortunately (for all tools that output names unqualified, like
ghci's browse) an identifier like "M.where" is unusable, because ghc
fails with:

  Qualified name in function definition

Otherwise (or nevertheless) I would invest an extra code line in the
lexer to rule out such identifiers.

C.