Parsing module without explicit module declaration fails

[waern]

If a module does not contain an explicit module declaration and starts with

-- | some comment

then parsing fails.

This is a bug in GHC's parser. It is only triggered if Opt_Haddock is used.

Details

GHC's parser has a rule for Haddock comments on module headers. When the parser sees the Haddock comment at the beginning it then wants the next declaration to be a module header (the grammar has an S/R conflict because of this).

One possible solution could be to parse Haddock comments separately from the Haskell code, and match up Haddock comments with AST nodes in a later step.

Steps to reproduce

-- | Hi there
main = print "Hello World!"

Running

$ haddock Main.hs

fails with:

Main.hs:2:1: parse error on input `main'

In contrast both of the following example work just fine:

{-
Hi there
-}
main = print "Hello World!"

foo = 23
-- | Hi there
main = print "Hello World!"

[SimonHengel]

#197 is a duplicate of this.