Fix issue 2128

[bmjames]

This is intended to fix #2128.

That issue relates to the error messaging from the parser; the two failing cases I have added need to be compiled manually to demonstrate that the error message is accurate:

[nix-shell:~/purescript]$ psc examples/failing/2128-instance.purs
Error found:
at /home/ben/purescript/examples/failing/2128-instance.purs line 8, column 9 - line 8, column 9

  Unable to parse module:
  unexpected !!!
  expecting expression

and

[nix-shell:~/purescript]$ psc examples/failing/2128-class.purs
Error found:
at /home/ben/purescript/examples/failing/2128-class.purs line 5, column 15 - line 5, column 15

  Unable to parse module:
  unexpected !!!
  expecting qualifier, proper name, (, {, _, "forall", "\8704" or identifier

If you think the testing should be improved to guard automatically against a regression, please could you give me some guidance on how to approach that?

[paf31]

Do we need this try? reserved "where" should either consume everything or nothing, there should be no reason to backtrack.

[bmjames]

You're right, try is superfluous here.

[paf31]

Thanks for this. Could you please update CONTRIBUTORS.md too?

[paf31]

Thanks!

[kritzcreek]

Cool!

[paf31]

I just realized this is on master. We'll have to remember to merge and cut 0.9.1 from master then.