patch applied (ghc-6.8/ghc): FIX Trac #1935: generate superclass
constraints for derived classes
igloo at earth.li
Wed Nov 28 13:39:26 EST 2007
Wed Nov 28 07:05:41 PST 2007 simonpj at microsoft.com
* FIX Trac #1935: generate superclass constraints for derived classes
This bug only reports a problem with phantom types, but actually
there was quite a long-standing and significant omission in the
constraint generation for derived classes. See
Note [Superclasses of derived instance] in TcDeriv.
The test deriving-1935 tests both cases.
M ./compiler/typecheck/TcDeriv.lhs -4 +31
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