#7167: Make it a warning (not error) to hide an import that isn't exported
---------------------------------+------------------------------------------
Reporter: simonpj | Owner:
Type: bug | Status: new
Priority: highest | Milestone: 7.6.1
Component: Compiler | Version: 7.4.2
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: None/Unknown
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
---------------------------------+------------------------------------------
We often see build failures like
{{{
Module `Prelude' does not export `catch'
}}}
elicited by an `import` statement
{{{
import Prelude hiding( catch )
}}}
John Lato and others suggest making this a warning, not an error. Simon
and I agree and we propose to do this for GHC 7.6, thus:
* Warn, rather than error, when a `hiding` clause mentions something that
the module does not export.
* Suppress with warning with `-fno-warn-dodgy-imports`, an existing
warning-suppression flag.
* Document the change, in the `-fwarn-docugy-imports` flag, and the
release notes.
We propose to make this change without a language extension. Doing so is
technically wrong, since H2010 says it's an error to mention something in
`hiding` that isn't exported, but it seems too heavyweight to make a
language extension just for this; and in any case it would have to be on
by default to be any use in practice.
Paolo, can you do all this?
* The relevant function is `RnNames.filterImports`.
* I suggest you make `lookup_ie` return `TcRn [(LIE Name,AvailInfo)]`
rather than the `MaybeErr ...` that it currently returns.
* The `want_hiding` flag is `True` if this is a hiding clause; in that
case `bad_ie` should warn (unless the warning is suppressed) rather than
error.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7167>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
