Re: [GHC] #4124: GHC rejects instance quotations with splices in the instance head

[GHC]

#4124: GHC rejects instance quotations with splices in the instance head
-+--
Reporter:  lilac |Owner:   
Type:  bug   |   Status:  new  
Priority:  normal|Milestone:  6.14.1   
   Component:  Template Haskell  |  Version:  6.12.1   
Keywords:| Testcase:   
   Blockedby:  4230  |   Difficulty:   
  Os:  Unknown/Multiple  | Blocking:   
Architecture:  Unknown/Multiple  |  Failure:  GHC rejects valid program
-+--
Changes (by simonpj):

  * blockedby:  => 4230


Comment:

 This too is related to #4230.

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Re: [GHC] #4124: GHC rejects instance quotations with splices in the instance head

[GHC]

#4124: GHC rejects instance quotations with splices in the instance head
-+--
Reporter:  lilac |Owner:   
Type:  bug   |   Status:  new  
Priority:  normal|Milestone:  6.14.1   
   Component:  Template Haskell  |  Version:  6.12.1   
Keywords:|   Difficulty:   
  Os:  Unknown/Multiple  | Testcase:   
Architecture:  Unknown/Multiple  |  Failure:  GHC rejects valid program
-+--

Comment(by igloo):

 I've fixed the pretty-printer so that it doesn't print `$[t| X |]`.

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Re: [GHC] #4124: GHC rejects instance quotations with splices in the instance head

[GHC]

#4124: GHC rejects instance quotations with splices in the instance head
-+--
Reporter:  lilac |Owner:   
Type:  bug   |   Status:  new  
Priority:  normal|Milestone:  6.14.1   
   Component:  Template Haskell  |  Version:  6.12.1   
Keywords:|   Difficulty:   
  Os:  Unknown/Multiple  | Testcase:   
Architecture:  Unknown/Multiple  |  Failure:  GHC rejects valid program
-+--
Changes (by igloo):

  * milestone:  => 6.14.1


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Re: [GHC] #4124: GHC rejects instance quotations with splices in the instance head

[GHC]

#4124: GHC rejects instance quotations with splices in the instance head
-+--
Reporter:  lilac |   Owner:   
Type:  bug   |  Status:  new  
Priority:  normal|   Component:  Template Haskell 
 Version:  6.12.1|Keywords:   
  Os:  Unknown/Multiple  |Testcase:   
Architecture:  Unknown/Multiple  | Failure:  GHC rejects valid program
-+--

Comment(by lilac):

 Some quick checking indicates the error message is using invalid syntax
 too: $[t| X |] is not accepted by GHC.

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[GHC] #4124: GHC rejects instance quotations with splices in the instance head

[GHC]

#4124: GHC rejects instance quotations with splices in the instance head
-+--
Reporter:  lilac |   Owner:   
Type:  bug   |  Status:  new  
Priority:  normal|   Component:  Template Haskell 
 Version:  6.12.1|Keywords:   
  Os:  Unknown/Multiple  |Testcase:   
Architecture:  Unknown/Multiple  | Failure:  GHC rejects valid program
-+--
 I think the following code should be accepted.

 {{{
 {-# LANGUAGE TemplateHaskell #-}
 class Storable a where
 data X = X
 [d| instance Storable $( [t| X |] ) where |]
 }}}

 GHC disagrees, saying:

 {{{
 test.hs:4:4:
 Illegal instance declaration for `Storable t_aKj'
 (All instance types must be of the form (T a1 ... an)
  where a1 ... an are type *variables*,
  and each type variable appears at most once in the instance head.
  Use -XFlexibleInstances if you want to disable this.)
 In the instance declaration for `Storable $[t| X |]'
 In the Template Haskell quotation
   [d|
   instance Storable $[t| X |] where |]
 In the expression:
 [d|
 instance Storable $[t| X |] where |]
 }}}

 This checking seems inappropriate before the type is actually spliced in!

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