Hi, Simon-
I'm currently trying to generate External Core for all the GHC
libraries and typecheck them using the stand-alone ext-core
typechecker (updated by me for the current incarnation of Core). I'm
running into a problem with the Data.String library. The generated
.hcr file includes, in part:
%newtype DataziString.ZCTIsString a
^ (DataziString.ZCCoZCTIsString :: ((DataziString.ZCTIsString) :=:
(GHCziPrim.ZLzmzgZR (GHCziBase.ZMZN GHCziBase.Char))))
= GHCziBase.ZMZN GHCziBase.Char -> a;
(Hopefully the syntax I introduced for newtype coercion decls is
obvious.) This coercion is saying that :TIsString equals ((->)
[Char]). But on the ext-core side, this doesn't typecheck because the
lhs has kind (*->*), and the rhs has type (?->*).
Is this a bug in GHC? It would be a pretty minor bug if so, since GHC
won't generate Core where the :CoZCTIsString coercion got used to
coerce anything that *didn't* have kind (*->*), but nevertless, the
coercion here isn't kind-correct according to the rules in fig. 3 of
the System FC paper (which say that both sides of the coercion have to
have the same kind.)
Note that there wouldn't be any problem if GHC didn't do the
eta-contraction thing for newtypes... but I don't know how easy it
would be to eta-expand again before printing out External Core.
Thanks,
Tim
--
Tim Chevalier * http://cs.pdx.edu/~tjc * Often in error, never in doubt
"Modesty...is both alien and irrelevant to people who are happy in
themselves, in their beings, in their skins, their natures, their
capacities."--Anne Sayre
_______________________________________________
Cvs-ghc mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/cvs-ghc
