#9173: Better type error messages -------------------------------------+------------------------------------ Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by schyler): Here's an error that a noob making a subtle typo might get from GHC: {{{ Prelude> map 1 [1..5] <interactive>:2:1: Could not deduce (Num (a0 -> b)) arising from the ambiguity check for ‛it’ from the context (Num (a -> b), Num a, Enum a) bound by the inferred type for ‛it’: (Num (a -> b), Num a, Enum a) => [b] at <interactive>:2:1-12 The type variable ‛a0’ is ambiguous When checking that ‛it’ has the inferred type ‛forall a b. (Num (a -> b), Num a, Enum a) => [b]’ Probable cause: the inferred type is ambiguous }}} I wholeheartedly agree that the information needs to be presented in a way that's easier to digest. For what should be a really simple error, I really have to stare that down to understand what it's actually trying to say ... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9173#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler