Ian Lynagh wrote:
Context if you haven't been following:
http://hackage.haskell.org/trac/ghc/ticket/1215
On Tue, Mar 13, 2007 at 03:12:33PM -0000, GHC wrote:
Interesting. It turns out I misinterpreted the Haskell lexical syntax:
GHC lexes `M.default` as `M` `.` `default`, because `M.default` is not a
valid qvarid but I neglected to take into account the maximal munch rule.
We have an open ticket for Haskell' about this:
http://hackage.haskell.org/cgi-bin/haskell-prime/trac.cgi/wiki/QualifiedIdentifiers
which was until just now
inaccurate (I've now fixed it). I propose to fix GHC in 6.8 to match the
Haskell' proposal.
If I understand correctly then the proposal would make e.g.
foo = Bar.where
a syntactically valid program, but one which would be guaranteed to fail
to compile with a not-in-scope error?
Wouldn't it be cleaner for it to be a lexical error? Unfortunately I'm
not sure how to say this in the grammar; the best I can come up with is:
program -> {lexeme | whitespace | error }
error -> [ modid . ] reservedid
Or make lexeme overlap with error, and do this:
program -> { lexeme_<error> | whitespace }
to make it clear that a valid program doesn't contain any error lexemes. But
then people might wonder why the error production doesn't contain all the
lexical errors.
I don't really have a strong opinion here, but I lean towards not doing this, on
the grounds that it's not strictly necessary and I'm a bit of a minimalist. The
compiler is already free to report the error as a lexical error if it likes.
Cheers,
Simon
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