[ ghc-Bugs-753777 ] Unboxed tuples as values

Bugs item #753777, was opened at 2003-06-13 07:16
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Category: Compiler (Type checker)
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Simon Peyton Jones (simonpj)
Assigned to: Nobody/Anonymous (nobody)
Summary: Unboxed tuples as values

Initial Comment:
Consider

  type T a = Int -> (# Int, Int #)

  f :: T a -> T a
  f t = \x -> case t x of r -> r

gives the following error message:

  ghc-5.04.1: panic! (the `impossible' happened, GHC 
version 5.04.1):
          codeGen/CgRetConv.lhs:83: Non-exhaustive 
patterns in function
          dataReturnConvPrim

Trouble is that 'r' is bound to an unboxed tuple.  This 
should fail, but in 5.04.1 it crashes the compiler.  In 6.0 
it's worse: the code will core dump because it enters R1.

But it should be rejected in the type checker.




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