some bugs in Language.Haskell.Parser

[Hal Daume]

The program:

> x =3D v where v =3D 2 where
>
> main =3D putStrLn "hello world"

parses as:

> x =3D v=20
>   where v =3D 2=20
>         main =3D putStrLn "hello world"

which is incorrect.

(in general, the parser can't deal with empty where clauses) as in:

> x =3D 'a' where
> class A a where

this gives a parse error because it's waiting for a real declaration
inside of the first where clause.

it also can't deal with empty statements:

> v =3D do {return 'a';;}

should be accepted but results in a parser error.

in Parser.ly, this essentially boils down to the fact that 'decllist'
must be nonempty, but in certain circumstances (all?), it really *can*
be empty.

the last error (with statements), can be fixed by replacing line
637-639:

> stmtlist :: { [HsStmt] }
>	: '{'  stmts '}'			{ $2 }
>	| open stmts close		{ $2 }

with:

> stmtlist :: { [HsStmt] }
>	: '{'  stmts optsemis '}'	{ $2 }
>	| open stmts optsemis close	{ $2 }

i believe.

 - Hal

 --
 Hal Daume III                                   | hdaume@isi.edu
 "Arrest this man, he talks in maths."           | www.isi.edu/~hdaume