#7856: Wrong error message for unknown Instance ------------------------------------------------+--------------------------- Reporter: bas | Owner: Type: feature request | Status: closed Priority: normal | Milestone: _|_ Component: Compiler (Type checker) | Version: 7.6.3 Resolution: invalid | Keywords: Instance Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Difficulty: Unknown Testcase: | Blockedby: Blocking: | Related: ------------------------------------------------+--------------------------- Changes (by monoidal): * status: new => closed * resolution: => invalid Comment:
I would not expect the "actual type" to be "String -> ()", but rather "IO ()".
You do get "IO ()", at least on 7.6.2 and HEAD: {{{ Couldn't match expected type ‛String -> IO ()’ with actual type ‛IO ()’ In the return type of a call of ‛sequence_’ Probable cause: ‛sequence_’ is applied to too many arguments In the expression: sequence_ lst In an equation for ‛tmp’: tmp = sequence_ lst }}} Given {{{tmp :: String -> IO (); tmp = sequence_ lst}}} the error message is clear: `sequence_ lst` is `IO ()` while the signature is `String -> IO ()`. I'm closing the ticket, but please reopen if you disagree. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7856#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler