Precedence errors are reported for undefined operators

[Olathe]

I found a misleading error message.

If I add the import for (<$>), but I forget to save the file

-- other imports
-- import Control.Applicative ((<$>))
main = print $ (+1).(+2) <$> Just 5

I get the error

    precedence parsing error
        cannot mix `(.)' [infixr 9] and `(<$>)' [infixl 9] in the same infix expression

which is rather hard to debug, since it makes it seem that the problem is either with Control.Applicative's precedence definitions or that I've somehow imported (<$>) with a different precedence from somewhere else.

It would be nice if it would report instead that (<$>) wasn't defined yet.

[Olathe]

It appears that (<$>) being undefined is reported in a later error message. I usually fix the first error reported, then move on to others, so it would be nice if it reported that it left out the precedence error for undefined operators entirely.

[simonpj]

A good idea for a snowy day

Mon Feb  2 16:44:50 GMT 2009  simonpj@microsoft.com
  * Improve error reporting for precedence errors

Possibly worth merging. But watch out... TypeRep now exports funTyConName so there's an import patch to Haddock that must go too:

Mon Feb  2 16:47:42 GMT 2009  simonpj@microsoft.com
  * Hide funTyConName, now exported by TypeRep

Simon

[igloo]

Both merged.