Re: [GHC] #7402: Warn about possible missing -XScopedTypeVariables on errors.
#7402: Warn about possible missing -XScopedTypeVariables on errors. ---+ Reporter: Aninhumer | Owner: Type: feature request | Status: closed Priority: normal| Milestone: Component: Compiler |Version: 7.6.1 Resolution: fixed | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Difficulty: Unknown Testcase:| Blockedby: Blocking:|Related: ---+ Changes (by simonpj): * status: new = closed * difficulty: = Unknown * resolution: = fixed Comment: Good point. I've tightened up the ambiguity check for instance declarations. Now you'll get an ambiguous declaration error from the above. Simon -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7402#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7402: Warn about possible missing -XScopedTypeVariables on errors.
#7402: Warn about possible missing -XScopedTypeVariables on errors. ---+ Reporter: Aninhumer | Owner: Type: feature request | Status: closed Priority: normal| Milestone: Component: Compiler |Version: 7.6.1 Resolution: fixed | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Difficulty: Unknown Testcase:| Blockedby: Blocking:|Related: ---+ Comment(by simonpj): Actually I was mixed up. The ambiguity fix would reject this instance, but the original question was about scoped type variables. The trouble is that this is a perfectly legal program ''without'' scoped type variables, with the 'n' meaning forall n. n. I'm not sure how to improve this. Simon -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7402#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
[GHC] #7402: Warn about possible missing -XScopedTypeVariables on errors.
#7402: Warn about possible missing -XScopedTypeVariables on errors. -+-- Reporter: Aninhumer | Owner: Type: feature request | Status: new Priority: normal| Component: Compiler Version: 7.6.1 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking:|Related: -+-- Suggest that the user they may wish to add -XScopedTypeVariables, if an error results from a free type variable which would be bound in its scope with the flag enabled. (i.e. if its name exists as a variable in the type declaration). I ran into this problem on code similar to this: {{{ instance (Sized a n, Nat n) = Rep a where emptyRep = replicate (toInt (undefined :: n)) 0 }}} and it took me some time to solve, and only by having vague knowledge that such a flag existed. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7402 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs