Re: [GHC] #4047: Incorrect unused-import warning in ghci

[GHC]

#4047: Incorrect unused-import warning in ghci
+---
  Reporter:  Berengal   |  Owner:   
   
  Type:  bug| Status:  closed   
   
  Priority:  normal |  Milestone:   
   
 Component:  GHCi   |Version:  6.12.1   
   
Resolution:  worksforme |   Keywords:   
   
Difficulty: | Os:  
Unknown/Multiple
  Testcase: |   Architecture:  
Unknown/Multiple
   Failure:  Incorrect warning at compile-time  |  
+---
Changes (by simonpj):

  * status:  new => closed
  * resolution:  => worksforme


Comment:

 I believe you may be misled by two things:

  * `ghc --make` does not recompile things that have already been compiled,
 and that can lead to lack of warnings if you do `ghc --make` right after
 (say) your `ghci` run.  Try adding `-fforce-recomp`

  * `undefined` is not a keyword: it is simply a named definition that is
 indeed imported from the Prelude. So there really is a difference between
 `[]` and `undefined` on the RHS of your definition.

 Everything seems to be working fine to me.  If you still thing there's a
 bug, by all means re-open this.

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[GHC] #4047: Incorrect unused-import warning in ghci

[GHC]

#4047: Incorrect unused-import warning in ghci
-+--
Reporter:  Berengal  |   Owner: 
  
Type:  bug   |  Status:  new
  
Priority:  normal|   Component:  GHCi   
  
 Version:  6.12.1|Keywords: 
  
  Os:  Unknown/Multiple  |Testcase: 
  
Architecture:  Unknown/Multiple  | Failure:  Incorrect warning at 
compile-time
-+--
 Try to load the following in ghci with -fwarn-unused-imports:

 {{{
 import Prelude hiding (zip)

 zip :: [a] -> [b] -> [(a,b)]
 zip _ _ = []
 }}}

 It spits out the usual warning for unused imports:
 {{{
 Warning: The import of `Prelude' is redundant
except perhaps to import instances from `Prelude'
  To import instances alone, use: import Prelude()
 }}}

 When compiled with `ghc --make -fwarn-unused-imports` no warning is
 printed. Also, the following does not generate a warning in ghci:

 {{{
 import Prelude hiding (zip)

 zip :: [a] -> [b] -> [(a,b)]
 zip _ _ = undefined
 }}}

 I expect ghci and ghc to agree on the warnings unless there's a good
 reason not to, and I do not expect warnings about declarations to depend
 on their implementation.

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