Precedence errors are reported for undefined operators
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.
Trac metadata
Trac field | Value |
---|---|
Version | 6.10.1 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |