compiler does not halt

[guest]

In the included tarball, run make in the code directory. The module ILPSAT takes over 11 minutes compiling. I have not seen it finish. I get the same result turning off the optimizing flags in the provided Makefile, as well as the -threaded flag.

[guest]

Code that elicits this bug.

[igloo]

I haven't tried to reproduce this yet as it depends on QuickCheck?. If anyone makes a small testcase then that would be useful both for diagnosing the problem and for putting in the testsuite once it is fixed.

[igloo]

This module (not well-typed):

module ILPSAT where

data Constraint a = Formula [[Proposition a]]
data Proposition a = Prop a
                   | Auxiliary [Proposition a]

transRHS :: [a] -> Int -> Constraint a
transRHS varSet b =
    if b < 0
      then Formula [[Prop (Auxiliary undefined)]]
      else Formula $
                [[Prop (Auxiliary varSet),
                  Prop (Auxiliary varSet)]
                ]

With 6.8.2 and the HEAD:

$ ghc -dcore-lint -c ILPSAT.hs -fforce-recomp -v
[...]
*** Renamer/typechecker:

at which point it appears to hang.

[simonpj]

Thanks for boiling this down Ian. Fixed by

Tue Feb 26 17:47:43 GMT 2008  simonpj@microsoft.com
  * Fix Trac #1899; missing equality check in typechecker's constraint simplifier

[igloo]

Merged