type definition with strict products

[S. Doaitse Swierstra]

Title: type definition with strict products

I a file that is too large to post here completely, I have used:

type Result  val s = (# val, Steps s #)

and I get the error message:

UU_Parsing.hs:391:

    Illegal unboxed tuple type as function argument: (# val, Steps s #)
    In the type: (# val, Steps s #)
    While checking the RHS of a type synonym declaration `Result'
    In the type synonym declaration for `Result'

using version "The Glorious Glasgow Haskell Compilation System, version 5.02.2".

Runningan earlier version of the compiler I get on the same file the following error message:

ghc-5.00.2: panic! (the `impossible' happened, GHC version 5.00.2):
        dsExpr: tuple pattern:
let {
  fail_d9jc
    = PrelErr.patError
        @ (b r,
           UU_Parsing.Steps a,
           UU_Parsing.Steps a,
           UU_Parsing.Exp a,
           UU_Parsing.Steps a)
        (PrelBase.unpackCString# "UU_Parsing.hs:735|case")
} in
  case ds_d9iL of wild_B1 { (# v, ds_d9iR #) ->
  case ds_d9iR of wild_B1 {
    UU_Parsing.Best l m f r -> (v, l, m, f, r); __DEFAULT -> fail_d9jc
  }
  }

Please report it as a compiler bug to [EMAIL PROTECTED],
or http://sourceforge.net/projects/ghc/.

which is not very informative either.

My questions are:

- is this type definition really forbidden, and what does the phrase "function argument " in the error message refer to?

- was there a restriction introduced about what one may write at the rhs of a type defintion between version  5.00.2 and  5.02.2?

 Thanks for looking into this,

 Doaitse Swierstra

 

-- 

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S. Doaitse Swierstra, Department of Computer Science, Utrecht University

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