New constraint solver: emitWantecCts

[simonpj]

David T says: I'm getting a panic when trying to build the listlike package with ghc HEAD on Mac OSX 10.7, using a 64bit build of ghc.

Building ListLike-3.1.2...
[1 of 8] Compiling Data.ListLike.FoldableLL ( src/Data/ListLike/FoldableLL.hs, dist/build/Data/ListLike/FoldableLL.o
)
[2 of 8] Compiling Data.ListLike.Base ( src/Data/ListLike/Base.hs, dist/build/Data/ListLike/Base.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.3.20111117 for x86_64-apple-darwin):
	emitWantecCts: can't emit non-wanted!

[simonpj]

Fixed by

commit 24d630a804d263184974afae65ffb3031a9cd13a
Author: Dimitrios Vytiniotis <dimitris@microsoft.com>
Date:   Thu Nov 17 16:39:54 2011 +0000

    Fix panic (missing keepWanteds) in simplifyApprox

 compiler/typecheck/TcSimplify.lhs |   24 ++++++------------------
 1 files changed, 6 insertions(+), 18 deletions(-)

Dimitrios is thinking about a test case

Simon

[dimitris]

Just pushed test case in testsuite (typecheck/should_compile/T5643.hs).