panic: ctFlavId: derived constraint cannot have id

[Lemming]

When trying to check, whether GHC-7.5 still suffers from #5970 I found another bug: When I compile the attached module I get the type error:

ghc: panic! (the 'impossible' happened)
  (GHC version 7.5.20120426 for i386-unknown-linux):
        ctFlavId: derived constraint cannot have id
    pty   = llvm-extra-0.4:LLVM.Extra.Extension.X86.Add'{tc rj}
              llvm-extra-0.4:LLVM.Extra.Extension.X86.D1{tc ri}
              llvm-extra-0.4:LLVM.Extra.Extension.X86.D1{tc ri}
              llvm-extra-0.4:LLVM.Extra.Extension.X86.D2{tc rh}

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

I tried hard to simplify the example and to remove all dependencies (llvm, type-level), but the test case is still rather involved.

Unfortunately it is again a problem with functional dependencies and I want to get rid of them anyway, but instead switching to type families and then to type level natural numbers I prefer to switch to type level numbers immediately.

[Lemming]

compiling this module let ghc-7.5.20120426 crash in type checking phase

[dimitris]

My bad, I know what is going on. It's a silly mistake (but I am amazed our testsuite did not show this yet!). I will push the fix and add the testsuite in a couple of hours. Many thanks for this testcase!

[simonpj@…]

commit 081ee177f3727a4c1bfad5897cab51e30c209521

Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Mon Apr 30 16:20:01 2012 +0100

    Egregious typo (fixes Trac #6055)

 compiler/typecheck/TcInteract.lhs |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)