Fix Trac #4966
authorsimonpj@microsoft.com <unknown>
Thu, 17 Feb 2011 14:10:00 +0000 (14:10 +0000)
committersimonpj@microsoft.com <unknown>
Thu, 17 Feb 2011 14:10:00 +0000 (14:10 +0000)
commita6c8ac78466af399df1372aa4f9271be32e73fcd
tree6851eb1e0a40c45d6a6474b9899b80d106fb5b3b
parent50d0293555691012f96259de7f8682b94db58517
Fix Trac #4966

This is just a program that exploits overlapping
instances in a delicate way. The fix makes GHC
a bit more friendly towards such programs.

See Note [Overlap and deriving] in TcSimplify
compiler/typecheck/TcSimplify.lhs