#5910: Holes with other constraints ----------------------------------------+----------------------------------- Reporter: xnyhps | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type checker) | Version: 7.5 Keywords: holes | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: Incorrect warning at compile-time Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: | ----------------------------------------+-----------------------------------
Comment(by dreixel): You might have to treat ambiguity errors in a special way. They can still be deferred with `-fdefer-type-errors`, and the error message adequately says there are two possible instances: {{{ No instance for (Show (Foo a0)) arising from a use of `show' The type variable `a0' is ambiguous Possible fix: add a type signature that fixes these type variable(s) Note: there are several potential instances: instance Show (Foo Bar1) -- Defined at Holes.hs:7:11 instance Show (Foo Bar2) -- Defined at Holes.hs:8:11 Possible fix: add an instance declaration for (Show (Foo a0)) In the expression: show (Foo undefined) In an equation for `test': test = show (Foo undefined) }}} So maybe you could use this in the feedback for holes with an ambiguous type. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5910#comment:10> 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