Wed Sep 5 10:07:30 PDT 2007 [EMAIL PROTECTED]
* Refactor, improve, and document the deriving mechanism
This patch does a fairly major clean-up of the code that implements 'deriving.
* The big changes are in TcDeriv, which is dramatically cleaned up.
In particular, there is a clear split into
a) inference of instance contexts for deriving clauses
b) generation of the derived code, given a context
Step (a) is skipped for standalone instance decls, which
have an explicitly provided context.
* The handling of "taggery", which is cooperative between TcDeriv and
TcGenDeriv, is cleaned up a lot
* I have added documentation for standalone deriving (which was
previously wrong).
* The Haskell report is vague on exactly when a deriving clause should
succeed. Prodded by Conal I have loosened the rules slightly, thereyb
making drv015 work again, and documented the rules in the user manual.
I believe this patch validates ok (once I've update the test suite)
and can go into the 6.8 branch.
M ./compiler/typecheck/TcDeriv.lhs -295 +245
M ./compiler/typecheck/TcEnv.lhs -13 +3
M ./compiler/typecheck/TcGenDeriv.lhs -102 +122
M ./compiler/typecheck/TcInstDcls.lhs -67 +59
M ./compiler/typecheck/TcMType.lhs -2 +69
M ./compiler/typecheck/TcSimplify.lhs -44 +5
M ./compiler/types/TyCon.lhs -4 +17
M ./compiler/types/Type.lhs -2 +8
M ./docs/users_guide/flags.xml -8 +8
M ./docs/users_guide/glasgow_exts.xml -108 +155
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