#8411: TypeSynonymInstances with partial type ----------------------------------------------+---------------------------- Reporter: wvv | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Resolution: invalid | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects valid program | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: ----------------------------------------------+---------------------------- Changes (by monoidal): * status: new => closed * resolution: => invalid Comment: Unfortunately, this is by design. Partial application of type synonyms is highly nontrivial; if done, it would require a large upheaval of type inference, and add a lot of complexity. For example, how GHC could know whether given `return :: a -> (a,a)`, is `Monad ((,) a)` or `Monad (RTuple a)` required? The situation gets much more complicated with larger synonyms, and things get ugly. I suggest to ask this question on haskell- cafe or IRC and leave two links found by a google search: #785, http://stackoverflow.com/questions/4922560/. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8411#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler