badness with -fmax-simplifier-iterations

[Hal Daume III]

A few things.  First of all, if you're stupid and say:

  ghc ... -fmax-simplifier-iterations=5

then ghc crashes with:

ghc-5.05: panic! (the `impossible' happened, GHC version 5.05):
        Prelude.read: no parse

Please report it as a compiler bug to glasgow-haskell-bugs at haskell.org,
or http://sourceforge.net/projects/ghc/.

(same thing happens in 5.04.2)

I think in DriverFlags.hs, the command for max-simpl... should be changed
from:

  Prefix (writeIORef v_MaxSimplifierIterations . read)

to

  PrefixPred (all isDigit) (writeIORef v_MaxSimplifierIterations . read)

Now, more importantly, it seems to obey this command unless you give it,
for instance, 0 as an argument:

  ghc ... -v5 -fmax-simplifier-iterations0 | grep 'Simplifier'


yields:

==================== Simplifier phase 0, iteration 1 out of 0
====================
==================== Simplifier phase 0, iteration 1 out of 0
====================
==================== Simplifier phase 0, iteration 2 out of 0
====================
==================== Simplifier phase 0, iteration 2 out of 0
====================


which seems pretty bad to me :)

 - Hal


--
Hal Daume III

 "Computer science is no more about computers    | hdaume at isi.edu
  than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume