#11099: Incorrect warning about redundant constraints -------------------------------------+------------------------------------- Reporter: diatchki | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.11 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by diatchki): I don't see how it is redundant---without that constraint I couldn't write the required type for the function: notice that the constraint is used to compute the type of the output from the type of the input. If I was to remove the constraint, then the connection between the input and output type is lost, and so uses of this function would become ambiguous in some contexts. In other situations (e.g., the function `get` [wiki:Proposal/CustomTypeErrors#ExtendedExample here]) this would be not just ambiguous but also plain wrong. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11099#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler